earth mat Flashcards
marks the path of the subducted plate as it descrnds into the asthenosphere
inclined seismic wadati benioff zone
3 devastating earthquakes along inclined seismic zones
chile 1909
alaska 1964
sumatra 2004
produced the banda aceh tsunami killed 300k in indian ocean region
sumatra 2004
which convergence occured thqt brought the closing of tethys ocean
convergence of india and asia
when did eurasia and india formed himalayan
40Ma
what is the limestone on top of mt.everest
chomolungma
which ocean was the limestone of mt.everesy priginated?
tethys ocean
how many elements were fiscovered
92
what is h1
h2
h3
protium
deutrium
tritium
varieties of garnet
almandine
andradite
grossularite
pyrope
spessartine
uvarovite
abdundant in pelitic metamorphic rocks including schists gneisses and granulites occurs ib laumbium rich pegmatites
almandine
metamorphosed carbonate rocks and skarns
andradite
grossularite
ultrabasic rocks inclusing mantle peridotes and kimberlites
pyrope
scarcer mineral in skarns
spessartine
scarce mineral in chrominum enriched ultrabasic rocks
uvarovite
haracterized by aggregates of sheaves of radiated
microscopic silica crystals that are often water
bearing
chalcedony
Stable at relatively low temperatures and
pressures; widespread in igneous,
metamorphic and sedimentary rocks
Alpha quartz
Stable at elevated temperatures and relatively
low pressures; occurs primarily in volcanic
rocks
Beta quartz
Stable at high temperatures and low pressures;
occurs in silica - rich volcanic rocks
Cristobalite
Stable at relatively high temperatures and low
pressures; occurs in silica - rich volcanic rocks
Tridymite
Stable at high pressures; occurs in meteorite
impactites, kimberlites and ultra high
pressure metamorphic rocks produced at
great depths
Coesite
Stable at very high pressures; occurs in
meteorite impactites and is theorized to be
an important constituent of the deep mantle
Stishovite
Stable at low pressures and fairly low
temperatures; forms around hot springs, in
soils and in ocean basins, especially as
accumulations of diatoms and radiolaria
opal
felsic utonice igneous to ks and pegmatites and meanirphic schists common variety is bright green amazonite tricilinc stubby crystals
microline
felsic plutonic igneous tovks metamorphic schists and gneisses monoclincic prismatic with evident symmetry
orthoclase
high temp kfels more transparent than others monoclinic
sanidine
what does IYGS stands for
international unuion of gelogical science
hydrous from secondary mineral 100-250
zeolite
By alteration of nepheline
in silica - undersaturated,
feldpathoidal igneous
rocks
Hexagonal; prismatic;
rare
Cancrinite
Scarce mineral in
metamorphosed
limestones/skarns
Isometric; equant; rare
Lazurite
In silica - undersaturated,
potassium - rich volcanic
rocks
Hexagonal; stubby
prismatic;
Leucite
In silica - undersaturated,
feldpathoidal igneous
rocks
.Hexagonal; prismatic;
rare
Nepheline
In medium – high grade
metamorphic carbonates/
skarns and pelitic schists,
gneisses
Tetragonal; prismatic;
square sections
Scapolite *
In silica - undersaturated,
feldpathoidal igneous
rocks.
Isometric; equant; rare
Sodalite
ZEOLITE GROUP
Isometric; equant; trapezohedra
Analcime
Trigonal; equant; pseudocubic
rhombohedra
Chabazite
Monoclinic; platy – capillary;
scaly – fi brous
Clinoptilolite
Monoclinic; prismatic – platy
Heulandite
Monoclinic; prismatic
Laumontite
Orthorhombic; prismatic – acicular;
radiated – fi brous
Natrolite
Monoclinic; tabular – platy; close
radiated, sheaf - like groups
Stilbite
what are the zeolites?
analcime
chabazite
clinoptilolite
heulandite
laumontite
natrolite
stilbite
feldspathoids group
cancrinite
lazurite
leucite
nepheline
scapolite
sodalite
what are granitic dikes
aplites
when melt of any composition comes in contact with water or air
quenching
eounded masses of radiating crystals
spherulites
cristobalite seed crystals grow into white snowflake forms
snowflake obsidian
glassy Si92 rich volcanic rocks higher water contents than obsidian
perlites
cloudy appearance and curved or subspherical cooling cracks
perlitic tecture
rocks contianing5-30% vesiclez
named by a modifier
Vesidular basalt
rocks less than 5% of vesicles
vesicle bearing basalt
cilicon and oxygen percent on earth
75% weight
94.7 by volume
the obly anion in the abundant elements of the eart
oxygen
what are the 4 common vcanic rocks?
rhyolite
dacite
andesite
basalt
what are the percents of volcanic rocks
> 66%
63-66%
52-63%
45-52%
what are under the feldspar group
calcite
potassium felds
sodium
sio2 concentrations tend to be enrich with minor elements suchc as
li be and ba
examples of minor elements
chromium
manganese hydrogen
titanium
phosphorus
remaining after melt remov has a different chemical co
position than ghe original parent rock id enriched in compatible elements and depted in incompatible elements
residual rock or restite
what are the incompatible elements
k rb sr and ba
enumerte the LREE
lanthanium la
cesium ce
praseodymium pr
beodymium Nd
samarium Sm
enumerate HREE
europium eu
gadolinium Gd
terbium Tb
dysprosium Dy
holmium Ho
erbium Er
thulium Tm
ytterbuum Yb
lutetium Lu
elements chsrwc as having a relatively high ionci charge guven raidus immobile tend to remain on restite
high field strength
valence charge trsce elements with a ratio of greater than 0.2 sre
large ion lithophile LIL elements
mobile in partial melts and useful in determining the role of hydrous fluid interaction and the parental osurce of the partial melt
large ion lithophile LIL
faure calculate the mean of this to distinguish between different magmatic environments such as ocean floor ocean islands and island arcs
Sr87/Sr86
mullen used this to identify the five basalts
MnO2 TiO2 and P2O5
minor elements to use the distungusihed the mod ocean eidge basalt and ocean island basalt
Rb sr Y nb
percent of minerals
felsic
intermediate
mafic
ultramfic
<40% Dark colored mineral
40-70%
70-90%
>90%
IUGS COLOR INDEX
<35% DCM leucocratic
35-65% mesocratic
>65% melanocratic
indirect scheme using data derived from chemical analysis of a rock samole first norm classification was deviae dby cross iddings pirsson and washington referred to as CIPW used in apahanitic or glassy volcanic rocks in modal cqnnot be determined
Normative mienralogy
rocks are charac by minerals with unusually high Al2O3 contents
peraluminous
rocks contain normative or modal minerals with unusually high K2O and/ or Na2O contents
peralkaline
rocks contain mafic minerals with average aluminum contents
metaluminous
rocks contain madic minerals with low alumnium concentrations
subaluminous
who was ghr skeme iniated the rock nomenclature in 1960 for IUGS
albert streckeisen
in the QAPF diagram what does plagioclase invludes
scapolite
feldspathoids included in QAPF
nepheline sodalite cancrinite leucite analcite nosean hauyne and kalsilite
less than 2% and 0.5 % Co2 and only the Na2O +K2O are plotted in the vertical
TAS
partial melting of rock magmas and lavas that solidify to produce igneous tocks in crust are formed by it produce
liquid melt fracrion enriched in lower temperature constituents and a residual rock component enriched in higher temperature refactory elements
anatexis
implies that solids and melt separate into isolated fractions that do not continue to react together during the melting process
fracrional melting
geothermal gradueng of upper 10km
~25C/km
geothermal gradient in old continental lithosphere
5-10C/km
geothermal gradient at hotspots ocean sprrqding ridges and volcanic arcs
30-50C
also known as adiabatic melting wc results a decrease in pressure and is related to rock depth whereby 10km depth corresponds approx 3.3 kbars
Decompression melting
agent that reduces the melting temperatureof a substance
flux
father of modern petrology
bowen
closed system diversification original nelt rvolves jnto one or more melts with different composition
differentiation
early formed crystals are segregated from the remaining melt early proponeyn of fractional crystallization
fractional crystallization
bowen studied in what university
carnegie institute of washington in 1910
studied rocks from a shallow igneous intrusion named situated in New Jersey west of new york ~2”” mys intrusion that consists largely of basuc rocks including basalt, diabase (coarse grained basalt) and gabbro
palisades sill
evidence for crystal settling and convective flow
Tertiary age Skaergaard Inteusion
tertiary age in greenland contains sedimentary like features such as cumulate layering graded bedding cross bedding and slump structures
skaergaard
one parent magma fractionated to profuce geo or more distinctly different daughter magmas with different composition
liquid fractionation
involves the preferential diffusion of select ions within the magma in response to compositional thermal or debsity gradients as well as water content plays a huge role in transport and concentration of metallic ores deposits in plutonic systems
differential diffusion
liquid liquid fractionation occurs when magma separates i to two or more distinct immiscible liquid phase
liquid immiscibility
liquid immiscibility was seen in
deccan traps
triassic jurassic rattlesnake hill basaly of connecticutr
gorceful injection of magma fractures the surrounding wall
stoping
country rocks that fall
stope and xenoliths r thw results
foreign crystals bot generated by crystallization of the sureoubding magma
xenocrysts
liemstones and schists xenoliths stoped into a granitic magma
thorr region of donegal, ireland
suites of rocks that form in response to similar geological conditions
pectrotectonic associations
sudden flood burst of glacial lake water or water contained within glaciet
jokulkhlaups
named for south america andes mountains wc overlie the peru chile trench by far the most common calc alkaline volcnaic ro k froming at convergent margins
andesite
high aluminum basalts
tholeiitic arc
qrz -phytic volcanic rocks intermediate between andesite and rhyolite tas 77%
dacite
also known as latites and shoshoniteslower TAS 57% SiO2 contain phenocrysts of andesine to oligoclasw pmagioclase feldspar amidst groundmass of orhoclase and augite
trachyandesites
> 69 % sio2
~68-73% SiO2 assoc with explosive silicic wruptions producing fragmental glassy and aphanitic to aphanitic porphyritic textures
rhyolites
rhyodacites
contian >20% qtz and plag metaluminous
grabodiorites
known as plagiogranites are granodioritic rocks in wc sodium plagioclase representd half to two thirds of the total feldspar components
trondhjemites
young island arc produce
tholeiite basalts which are doung in oceanward side of volcanic arc newrest the rench boninites adakites
high Mg untermediated 52-68% groundmass contin phenocrysts of opx lack plag pehnocrysts encriched in chromium nickel volatile elements lree deelted in hree and hfs occur proximal to the trench bear geochemical signatureprodyct of subduction related arc systems high temp loe pressure remelting
boninites
silica srayrated >56% high lree low hfs derived by slab melting of eclogitw and garnet amohibolite from the deacending ocean lithosphere knly form where young think hot ocean kithosphere subducted beneath island arc lithosphere known to form at contiennt continetn colkision sites as a result of shallow slab subduction plutonic equivalent is trondhjemites and tonalites
adakites
an px bearing suite of rocks of generally granitic composition occur in ttg
charnockites
ttg aasoc oxcur in archean rocks
pilbara craton of australia and the bear-tooth and big horn mountains of wyoming
dark colored potassium rich trachyandesitws containing olivine and augute phenocrysts with a groundmass of labradorite leucite thickened lithospeherw fartehst from the trench rwgion in continent continent collisions in backarc basins
stoshonites
plutonic equivalent of rhyodacite and rhyolite
granitoids
used for silica oversaturated plutonic rocks that contain essential potassium feldspars and quartz form at mayyrw convergent margins tend to be peraluminous to metaluminous
granitoid
form by partial melting of basic to intermediate igneous rocks i namor above yhe subduction zone at ocean ocean or ocean continent convergent margins
i type granites
peraluminoud potassium rich s type granites and granodiorites are prticulary common at continent continent collisions
s type
detived from phyllosilicates minerals in graywackes and mudstones of the continental crust and accretionary wedge. peoduce two mica granites containing biotite and muscovite
perlauminous sedimentary
20-60% and 35-90% alkali to plagioclase feldspars assoc with precambrian cratons and convergent margins
granite
mantle derived larental magmas low Sr87/Sr86 rations <0.704 assoc with calc alkaline tonalites qtz diorites and gabbroic rocks degelop in island arc settings copper and gold mineralizations
m type granites
melting of an ig wous protolith from wither the downgoing oceanic lithosphere or the overlying mantle wedge enriched in Na2O and Ca2O and contain lower Al2O3 concentrations less than 0.708 derived from a mantle source enriched in mafic minerlas porphyry copper tubgsten and molybdenum prevalent along the mesozoic cenozoic andes mountains
i type granites
sedimentary crustal rocks in collision zones depleted in Na2O but enriched in Al2O3 peraluminous. >7.08 earlier se cycle. also known mica granites contain both muscovite and biotite rich in phyllosilicate mienrals tin deposists assoc with
s type granites
anorigenic produced by activitws that do not involve the subduction and collision of lithospheric plates enriched in akaline elements depelted in Mg Ca Al Cr Ni mote enriched ib LIL elemenyd and depelted in refractory elements peralkaline alkali rich
a type granites
fault bounded mark the site of present or former convergent margins been transporrted far from thwir site of irigin by thrust faulting and shearing
dismembered into fault blocks and junbled together in a haphazard fashion contain disrupted pelagic sediment layers basalt cumulate basic and ultrabsic layers and assoc with tectonic melanges
alpine orogenic complex
sheared heterogeneousrock assemblage embedded within a highly deforemed mud matrix form at subduction zones miced withcrocks formwd in forearc settings slices of eclogite peridoite and blueschist
tectonic mélanges
alpine presefved in orogenic belts serpentizied in the alps known as steinmann trinity types consist pelagic chert serpentinite hydrothermally altered peridotite and spilites (altered pillow basalts)
ophiolites
develop due to the extensional tectonics result in backarc spreading or forearc spreading
chromium petrotecronic
suprasubduction zone SSZ ophiolites
pricess by which epiclastic sediment transportation is initiated by erosion is
entrainment
occurs when mienrals such as clays and micas expand when wetted
slacking
rwsult from changes from daily seasonal in rock temperature
insolation
zone of
accumulation, is characterized by enrichment
in some of the constituents leached from the
A - horizon. The process by which materials
are translocated downward to be added to
the lower part of a soil is known as illuviation.
B - horizon
The process by which materials
are translocated downward to be added to
the lower part of a soil
zone of illuviation
commonly gives the
B - horizon a distinctly reddish or yellowish
humid climates, reprecipitation of
amorphous or crystalline iron oxides (e.g.,
hematite = Fe 2 O 3) or hydroxides (e.g.,
limonite ≈ FeOOH)
In humid climates,
where chemical decomposition is thorough,
clay minerals and bauxite are also concentrated in the B - horizons to form aluminum -
rich horizons.
n dryer climates, calcium carbonate
(CaCO 3) precipitates, producing B k soil horizons. In many cases, mineral precipitation in
the B - horizon binds soil particles together
into hard, nodular zones or into completely
indurated sub - horizons called
duricrusts.
most common examples of duricrusts are
the calcium carbonate
calcrete or petrocalcic
arid, desert climates.
Similar hard sub - horizons of silica and gypsum
( silcrete )
( petrogypsic
are partially cemented clods
of soil particles of various sizes that give
the soil a crumbly lump appearance.
Peds
hich are concentrations of illuviated material such as clays or iron oxides
that occur as layers or that envelope less -
altered cores.
Cutans,
which are prolate to equant
hard lumps formed by mineral precipitation and include concretions and nodules
of all sizes.
Glaebules
called the soil mantle ,
represents moderately to minimally weathered, slightly altered materials that are
transitional to the underlying, unaltered
parent material.
Where soils are developed over bedrock,
the largely unweathered bedrock constitutes
the so - called R - horizon or regolith horizon.
C - horizon,
has organized
soils into 12 major orders, which are fairly
easy to learn (Figure 12.20 ). Each order is
subdivided into as many as seven suborders
of which there are a total of 64. The suborders are subdivided into more than 300 great
groups, which are subdivided into some 2400
subgroups, which are further subdivided into
families and lastly into soil series. Some
19,000 different soil series have been mapped
in the United States alone
e USDA - NRCS (1999)
was developed with the endorsement of the
International Union of Soil Scientists (IUSS)
and the Food and Agricultural Organization
(FAO) of the United Nations. It divides soils into 25
orders and 98 groups based on the physical
characteristics of the soil
Unlike the USDA -
NRSC classifi cation scheme, climate is not
considered in the WRB. The long - range goal
of these efforts is to promulgate adherence to
a single standard worldwide soil classifi cation
scheme.
1998
a world reference base (WRB) for soil sciences
Most geotechnical and engineering personnel in the United States use th
soils are given
names and symbols according to their particle
size distributions, notably the proportions of
gravel, sand, silt and expansive clays, and to
the content of non - expansive clays and organic
materials in the soils. Engineering defi nitions
of gravel, sand, silt and clay do not correspond exactly to those used by geologists,
who employ the Wentworth – Udden grade
scale (W - U scale)
Unifi ed Soil Classifi cation System
where particle diameters
exceed 4.0 mm (as compared with 2.0 mm
in the W - U scale).
Gravel (G),
where particles range from 0.074
to 4.0 mm (as compared with 0.0625 –
2.0 mm in the W - U scale
Sand (S),
where particles range from 0.004
to 0.074 mm (as compared with 0.004 –
0.0625 in the W - U scale).
Silt (M),
which are defi ned in the same
way in both systems as particles smaller
than 0.004 mm (4 μm). The USDA - NRCS
classifi cation system, however, defi nes
clays as particles smaller than 2 μ m.
Clays (C),
Gray to brown A - horizon epipedon; B sub - horizons
rich in clays with reasonably high concentrations
of bases such as Ca, Na, Mg; reasonably high
moisture content
Relatively humid areas with sparse
forest or savannah cover; base and
water content yield fertile soils
Alfisols
Weak horizon development; rich in disordered
clays and Al – humus complexes; high
phosphorous retention; good moisture capacity
and cation exchange capacity
Form in a wide range of non - arid
climates; mostly on volcaniclastic
materials; tend to be quite fertile
Andisols
Sparse organic material in A - horizon epipedon;
well - developed B - horizons, often rich in Ca -
carbonates, even gypsum; low moisture content
for long periods of time
Dominate in arid regions with sparse
rainfall and vegetative cover; suitable
for agriculture only if irrigated
ardisols
Lack signifi cant soil horizon development; soils
only because they have the capability to support
rooted plants; often sand rich
Occur in any climate or setting; mostly
on young surfaces; also in chemically
inert parent materials or on slopes
where erosion occurs
entisols
Permafrost soils and soil features; patterned
ground, broken horizons and incorporation of
organic matter in lower horizons produced by
frost heaving and churning
In high latitude and/or high elevation
areas where soils freeze for long
periods
gelisols
Mostly very organic rich O - horizon; deeper
horizons tend to be poorly developed, if at all
Mostly peat and muck from partially
decomposed plant debris in swamps
or bogs or water - saturated soils in
areas of poor drainage
histosols
Weak horizon development; less clay concentration
in B - horizon than alfi sols; carbonate and
silica - rich B - horizons may occur; reasonably high
moisture content
Form in a range of non - arid regions
from subpolar to tropical; often with
forest cover; less suitable for
agriculture than alfi sols
inceptisols
Very dark, thick, organic - rich O and A epipedon;
high base content, especially calcium; clays with
high cation exchange potential
Common under grasslands in semi - arid
plains and steppes with seasonal
moisture defi cits; some under forest
cover; great for grain production
mollisols
Weak horizon development; extreme decomposition
and base depletion; clays, mostly kaolinite, with
low cation exchange capacity; bauxite under
extreme conditions; quartz and iron oxides
Develop over long periods of time in
tropical/subtropical settings with
high rainfall and thick vegetative
cover; generally infertile
oxisols
Thick O - horizon; well - leached A - horizon with low
Fe, Al, Ca; well - developed B - horizons with clays,
reddish iron oxides or black humic material;
good cation exchange
Dominate under coniferous forests; in
areas with reasonable rainfall;
generally suitable for agriculture
spodosols
Well - leached A - horizon with some organics;
clay - rich B - horizons with generally low base
contents as Ca, Na and K are largely removed
which distinguishes them from alfi sols
Humid climates; low base content;
soils unsuitable for sustained
agriculture unless fertilized with Na
and K
ultisols
High expansive clay content; large changes in
volume associated with wetting and drying;
cracks when dry and other evidence of soil
movement; may have horizons
Poor soil for structures given the
volume changes and tendency for
strength and plasticity to change
during wetting and drying
c
vertisols
<5% fi nes; continuous size variation over a range Well - graded gravel GW
Clean gravel
<5% fi nes; mostly one size or polymodal Poorly graded gravel GP
Clean gravel
> 12% fi nes; mostly silt Silty gravel GM
12% fi nes; mostly clay Clayey gravel GC
Dirty gravel
<5% fi nes; continuous size variation over a range Well - graded sand SW
C>5% fi nes; mostly one size or polymodal Poorly graded sand SP
lean sand
> 12% fi nes; mostly silt Silty sand SM
Dirty sand
re those
that contain more than total 50% sand and
gravel by weight. Gravels contain more gravel
than sand, whereas sands contain more sand
than gravel. Coarse - grained soils are further
subdivided according to the percentage of
fi ne - grained components (clays + silts).
Coarse - grained soils
contain less than 5% fi nes
Clean
soils
contain more than 12% fi nes
dirty soils
contain
more than 50% silt plus clay. Silts are defi ned
as soils with more silt than clay, whereas clays
contain more clay than silt. Fine - grained soils
are further subdivided according to their mica
content, organic content and their degree of
plasticity. Highly organic soils are prone to
compaction, dehydration and decomposition
resulting in volume loss, which makes these
soils unsuitable for construction. Soil plasticity is largely determined by the soil ’ s ability
to absorb water and therefore by their smectite (expandable lattice) clay content. As will
be seen in the following section, plasticity is
an extremely important measure of the
mechanical properties of soils and allows one
to predict how they will react in different
circumstances. The “ L ”in the group symbols
stands for loam, a soil that contains appreciable amounts of both silt and clay in the fi ne
fraction.
Fine - grained soils
is the amount of stress a soil can
bear without failing by rupture or plastic
fl ow. It is an expression of the ability of a soil
to resist irreversible deformation such as inelastic changes in shape, volume and position.
Strong soils are quite resistant to stress and,
along with many kinds of bedrock, generally
provide excellent substrates for buildings.
Weak soils are subject to compression, collapse or fl ow when stressed and therefore
provide poor substrates for structures
Soil strength
Problems for engineers arise because soil strength
can change, especially in response to changes
in water content (Box 12.3 ), so that formerly
strong soils loose strength and become weak
soils that fail by rupture, fl ow plastically or
even fl ow like a liquid.
The measure of a soil ’ s tendency to change
strength is expressed by
measure of the change in soil strength that
results from changes in water content and
various kinds of disturbances such as vibrations, excavations and loading that stress
soils. Soil sensitivity in response to water
content, easily determined in the lab, is commonly expressed by Atterberg limits that
permit the subdivision of fi ne - grained soils
into four classes on the basis of how they
behave as their moisture content changes
(Figure 12.21 ).
soil sensitivity
soils, (3) plastic
soils, and (4) liquid soils. The boundary
between brittle solids and semi - solid soils is
which is the
water content below which soils do not shrink
as additional moisture is lost during drying
shrinkage limit (SL
Above the shrinkage limit,
semi - solid soils shrink and crack as they lose
moisture and become progressively more stiff
and brittle. Soils that remain brittle or semi -
solid under all conditions of potential moisture content tend to be strong and provide
excellent substrates for most construction
projects so long as they are not loaded beyond
their rupture strength. Solid bedrock is even
better
eparates semi - solid
soils from plastic soils and is the water content
at which soil deformation changes from
rupture to plastic fl ow (Figure 12.21 ). Plastic
substances change shape and/or volume in
response to stress or pressure but do not
rupture visibly. Because they retain cohesive
strength, they do not fl ow like a liquid. Plastic
soils are moisture sensitive in that their
strength decreases and they deform more
easily as they become progressively less cohesive with increasing moisture content. This
helps to explain the many slope failure incidents that occur following heavy rainfall and
the concurrent infi ltration of groundwater
into soils.
plastic limit (PL
of a soil is a measure
of its cohesiveness, which is sensed as a sticky,
cohesive feel to the touch. It generally increases
with clay content (especially expandable
smectites) and water content. Soils with low
clay content tend to be relatively non - cohesive
and therefore possess relatively low plastic
limits. Soils with high clay content tend to be
much more cohesive and to possess signifi -
cantly higher plastic limits. Because plastic
soils deform when loaded, they do not make
good substrates for major construction
projects
plasticity
separates plastic soils
from liquid soils (Figure 12.21 ). It is the water
content at which soils lose their shear strength
and begin to fl ow. When a suffi cient amount
of moisture has been added to a soil, it may
begin to behave as a liquid; that is, it will
loose cohesive strength and begin to fl ow
under its own weight. This can have disastrous consequences for the structures placed
such soils. The liquid limit tends to be rela-
e liquid limit (LL)
contain less than 30% gravel in their detrital fraction and contain mroe sand
sands and sandstones
epiclastic sediments contain 5-30% gravel in ghe epiclastic fractuon
gravelly sands or gravelly muddy sandstones
if a sandstone contains less than 5% gravel and has a sand:mud ratio greater than 9:1
pure sand (arenites)
they pxcupy the four sectiond in the bottom left portion of folks GSM diagram
mudrocks
less than 5% gravel
sandy muds and sandy mudrocks with san mu ratio >1:9
this prefix can be sued if any gravel occurs in the muds or mudrocks
gravel bearing
they occupy the six sectors in the bottom right portion of GSM
sands and sandstones
an attmeot to represent the thpical particle size in the population and detrital grain populations can be described by 3 lf this
central measure
which a best fit line is plotted for similar data
frequency curve
most anudnant particle size easily determiend when size data are plotted in a historgram
mode
particle size such that half the population is larger and half is smaller
median
large meteor that explodes in space
bolides
areas where bolides collided with earthes surfaces producing inpactitites
breccia
A well-sorted, matrix-free conglomerate, which forms where the sediment transported and deposited comprises only pebble and gravel grades.
sieve deposits
fault collapse and rockfall breccias are oligomictic composition:
mature, quartz rich conglomerates
produced by barious combinations of sedimentary and tectonic processesthat mic several rock types and tectonic prcosses that mix seceral rock types are
melanges gravelstones
this decompose less rapidly and are more common preserved in gravelstones derived from magmatic atc and i tracratonic rift
Granitoid rock dragmentd
generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz-poor monzonites to quartz-rich quartzolites.
granitoids
ise dto documeny strike slip on the san grabriel fauly in southern california
ridge basin breccia
part kf major transfom plate australia and pacific plate
alpine fault
recognized unusual clasts derived from ultramafic rocks and greenschist amohibolite grade schists in pliocene conglomerates deposited i cascade valley
sutherland
minimum eight lateral slip on the alpine since 3.6 Ma has been 27km/Ma up to
35km/Ma
detived from caples and toesse terranes wc are now lcoated 420 mn to the southwest of the
maruia basin
abergae dectral slip on the alpine fault is
37km/Ma
sandstone stuat contain 75-95 quartz and have more feldspar then lithic feagments
sub arkoses
less than 75% Q plit in one of the four sectors in the bottom portion
submature to immature arkose
those with neglible mud matrix and in boundary at 5%mud
arenites
uplofted recycled accretionary complexes
subduction complexes
exposed in orogenic belts some distances from convergent plate boundaries
foreland uplifts
consists of stable cratonuc areas that are divided into shields and platforms
continental block source areas
consist primarily of precambrian plutonic and high grade metamorphic rocks such as granitoids gneisses and grnaulitws
shields
charac bt a relatively thin veneer of largely mature detrital sedimentary rovks and or carbonate sedimentary rocks that overlie sgield rocks
platforms
sediments are derived from pre existing mature and sed rocks overly plutonic basement rocks in a stable platform setting with very low reloef
craton interior
both platform sed rocks and plutonic basement shod rocks are exposed as soruce rock thpes in settings of low to moderate relief
transitional cratons
basement of plutonic igenoud and metamorphic rocks are exposed in an area of high relief resilting drom uplift along dailts in contintental aetting
uplifted basement
produced by the minimal decomposition of ferromagnesian mienrals and commonly from in alkaline soils with impeded drainage high latitutdes where precipitation and temperatures arw low
chlorites
product kf the weathering kf ferromagnesian minerals plud plag favored impeded drainage alkaline conditions and semi arod climates
smectites
common products of weathering of feldspars k felds most common in temperated region soils with near neutral pH
illites
common in mod latitudes semi arid to temperate soils witj slightly alkaline pH
mixed layer illite-smectite clays
warm humid acidis soul common i nsubtropics cations tend to be leached from inetrlayer sites gives rise to degraded illites and kandites such as
kaolinite
wam humit high acidity low pH intense deomposition allows silica to sissolve readily giving rise to
gibbsite and ohter minerals of the bauzite suite
comkon at high latitudes
chlorites
common at low latitutdws
kaolinite
common in younger tertiary rocks
smectite clays and smectite illite
older rocks dominated by illite
potassium iron rich illite produced in marine envi dome generated in slow precipitation oxidizing envi also forms by relacement of fecal pellets under marine conditiond are reducing its sand grains occur as disseminated grains in sands in areas ate detrital influx large indicateor of of marin sedimentation
glauconite
colmonly form around decomposing organic matter that reduces iron enabling it to he removed in wolution
redcutipn spots
smectite rich claystones for
ed by the alteration of colabic ash deposits generated by explosive eruptions
popcorn liek
bentonites
used for organic rich mudstones and claystones
sapropel
oil cam be extracted by rhe process of
pyrolysis
bituminous oragnic material in mudrocks buried and heated to 100-140 ac is converted into petroleum and when heated into petroleum and when heated over 160 converted into natural gas
kerogen
where is sapropel in jurassic found
connecticut
later deeper diagenesis
mesodiagenesis
shallow diagenesis that lccurs as sedimentary rocks approach the sirface due toverosion
telodiagenesis
creation of this can reduce the porosity of lithic sanatones and conglomerates making them less efficient storwrs and transmitters of fuids
psuedomatrix
most common between grains i quartz sands and gravs with little or no plastic mateix and occurs less frequently in feldspathic sands and gravels occurs ober a range of depths and causes significant decreases in porosity
pressure solution or pressolution
one phase is more soluble than the other
concavo convex
what are the major cements in detrital sedimentafy rocks?
silica minerals cl
carbonate minerals
iron oxides and hydroxides feldsprs and clay minerals
quartz occurs chiefly in the form overgrowths in which the silica that lrecipitatws drom pore solutiond i itially nucleates on a pre existing detrital quartz grain
syntaxial quartz
morw soluble in alkqline waters than in mildly acidic waters common cement in volcanoclastic sediments a decrease in pH can cause cement precipitaiton but an increse can cause dissolution
opal
bladed commonly a radiating to divergent havit when observed under a petrogrpahic microscope
chalcedony
any lrocess that removws carbo dioxide from subsurface waters raises the pH making them more
alkaline
composed of one or more calcitw crystals that occupy small pore spaces bwteen settital grains
blocky cement
composed of si gle large calcite crystals that nucleates and grows to fill multiple pore spaces so tht it completely envelops several detra grians which appear as inclusions within a si gle calcite
poikiloptic cement
common in sedime ts deposited in failry arid terrestrial environemnts such as alluvvial fans braided streams and meandering stream channels and flood plains and deserts
hematite
occurs as stacks of platy layers called books preciipitate fairly shallow depths feom low potassium acidic pore waters during eodiagenesis and telodiagenesis acidic pore waters are common in continental settings
kaolinite cement
forms at higher temperatures and deths from high potassium alkaline pore waters especially in marine settings form mostly during late eodiagenesis and mesodiagenesis
illite cement
when k felds is altered and this is the fine grained mica related to nuscovite
sericite
at higher tenepratures both calcium and potassium deldspars are altered to
albite
volcanic fragements during progressive burial and diagenesis alter to
zeolite minerals
become unstable and are transformed into mixed layer clayes above 100C
smectite
converted into illite or chlorite above 150C
kaolinite
mixed layers clays transformed into more ordered illite above
200
all clay minerals are transformed into these above 300C
chlorite or micas such as muscovite
zeolite minerlas stable at 100
and stable from 100-200
and 200 above
analcime and heulandite
laumonite
phrenite and pumpelyite
transitional between diagenesis and low grade metamorphic process very low grade ascribed to this
zeolite or prehnitr punpellyite facies
form by the precipitation of material around a nucleation surfac esuchas fossil sand grain or shale chip wether outcrops as cannon ball like structures precipitation of kienral cmeent such as linonite or hematite
siderite purite marcasite form under reducing conditions and calcite is common formed under the ozidizing reducing conditions
concretions
similar to contetions but lack a well defined nucluse and generally lack concentric growth ringd
nodules
increasingly soluble as pH decreases and acidity increases
limestones
charac by mienral filled cracks whose origin remains unknown
septarian nodules
this orginate as nodules or concretiond of calcite or anhydrite and in acidic the exteriors are replaced by chalcedony
geodes
common in detrital sed rocks in carbonate iron rich cmenetd mimic stratification secondary features often truncated against promintent joint surfaces form by lrecipitation of various iron oxide minerlas moving througj bodies of rock separated by fractures
liesegang bands
fluids moving into such bodies of rcok from the outside in often produce ring like parterns of bands
liesegang rings
less than 4% mg
low magnesium calcite
more than 4% mg
hogh magnesium calcite
carions of substitute for calcium
strontium
most unstable during diagenesis especially in meteoric water whereas low mg is stable t
aragonite that’s why aragonite and high mg calcite is not lresent in older rocks
in solid solution with ankerite and abudnanc ein increase with age in ancient carboante sed rocks especially in precambrian
dolomite
carbonate mineral
siderite!! 😭
mor ebaundant in ancient than in modern carboante sequences
Low Mg calcite
more abudnant in modent tuan in ancient
high mg calcite
more abudnant in mdoenr than in ancient carbonate sequences
aragonite
mroe ahundant in ancient than in mosent carbonate sequnces
dolomite
cabroante shells begin dissolution becomes significant ata dpeth becomes complete where bottom waters are sufficiently cold and acidic below depth all caco3 is dissolved
lysocline
tropics occurs @ 4000-5000 m
carbonate compensation depth CCD
of the amount of detrital sediment flowing into an area exceeds carboante production and preservation
carbonate bearing detrital sediment fossil bearing sandstone will form instead of wottle or no detrital sediment cotnent
sand pr gravel size clastic particles called grains or
allochemical constituentd allochems
mud sized particles called mud or
micrite
prginacally bound accumulations of carbonate called
boundstoe s or biolithites
clasts of carbonate sediment
limeclasts
soherical concentrically laminated sand sized particles possess a nucleus form by accretion of calcium carbonate laminae about a particle such as a shell fragment or sand grain that acts as a nucleus for precipitation can radial calcium cavornate structures involve in endolithic bacteria such as cyanophyted indication of shallow amrine wave or tidal cureent agitated wnvi of deosition in tropical or subtropical setting
ooids
gravel sized clasts of cohesive carbonate sediment produced when clasts of cohesive carbonate sediments or sed rocks are eroded most are derived nearby coeval deposits of cohesive deposition derived intraclasts
limeclasts
erosion of older source rockd outside the area of deposition are called
lithoclasts or extraclasts
are produced when partially demented grain clusters are eroded during storms encrusted in cyanophyted carbonate laminae may form transforms to botryoidal graisn
grapestone
resemble ellipsoidal fecal pelleted excreted by many organisms
peloids
coarser carbonate mud particles are called
macrospar
large modern carbonate mud is produced by thid
calcareous green algae tusy secrete fine needles of aragonite upon decomposition needles are release generating carboante mud
micro boring activity of blue green cyanophyte bacteria and algae accom by precipitation of carbonate in micropores converts original carbonate materail into micrite
micritization
who introdurc rudite lutite arenite
Grabau
emphasizes the tecture of carbonate rocks utilizing rarher simple terminology
dunham’s classification
less than 10% grains
mudstone
more than 10% grains
wackestone
contain interstitial diagenetic mienral cements rhat bind the grains together
grianstone
no depositional texture is recognizable
crystalline carbonate
produ ed by organisms that build rigid organic structures such as reefs by secreting the calcium carbonate
framestone
produced by organisms that build organic strutures sich as stromatolites and reefs by binding and encrusting pre-existing carbonate material
bindstone
generated bu organisms that trap carbonate sediment by acting as baffles that hinder its movement across the bed causing it to be trapped process in reefs and bioherms
bafflestone
carbonate bearing rocks with a matrix supported framework
floatstone
precipitated in the pore spaces between allochems during diagrnesis
sparry cements
25% intraclasts in allochem population are given
intra
if the interstices between intraclasts are largely filled with diagenetic cement the rock is
intrasparite
if filled with mud
intramicrite
fewer than 25% intravlasts occur the rock contains more than 25% ooids the bames are
oosparite and oomicrite
if neither intraclasts nor ooids exceed 25% of the allochems then
fossils and pellets or peloids dominate
micrites that contain small spar filled voids produced during diagenesis
dismicrite
in situ carbonate accumulations roughly equivalenh to Dunhams boundstones
biolithite
rocks with at leadt one third of both spar and micrite between allochems
poorly washed sparites
<1% allochems
allochemical micrite
1-10% allochems
sparse allochemical micrite
> 50% allochems
packed allochemical micrite
aimplest distribution of carbonate depositional envi occurs on where the idela model the bottom slopes gently seaward over fistances develop on the margins of shallow subtropical seas environments occupy roughly shore parallel bands charac by warer depths gradually increase seaward
carbonate ramps
ideal carbonate ramps
supratidal
intertidal
subtidal avove normal wave base
subtidal above storm wave base
subtidal below wave base
where do carbonate found
low relief intracratonic platforms or passive margins or in oceanic environments far from land
develop newr shelf or platform margins where nutrient rich waters upwelling from depth encourage the development of carbonate buildups (wc creates a queit water lagoon on the landward side) such as reefs and sand shoals
rimmed platforms
what is the ideal landward to seaward sequence of environments
supratidal
intertidal
lagoonsl
reef or subtidal sho/island with local tidal channel
reef flank/platform slope
deepeater mass flow l/pelagic
develop during sea level high stans when oceans flood dissolution of grains composed of aragonite or high magnesium calcite produces
form of ooids and fossils is preseved as a cavity of similar shape
moldoc porosity
cements that nicleate on grains grow at similar rates to produce coatings if nearly constant thickness
isophacous rim cements
composed of low magnesium calcite
meteoric cements
involves the nucleation on host grains of multiple crystals that grow outward into pore spaces to produce a fri he of crystals with striagjt boundaries whose size increases away from the host grains
drusy calcite
involve the precipitation of low mg calcite that nucleates in optical continuity with a low mg calcite grain
syntaxial calcite
consists of a si gle crystal large enougj to incorporate multiple grains during its growth
poikiloptic calcite
continued lrecipitation on grain bottoms leads to the development of that hang downward from the grain
pendant cements
carbonate rocks new crystals form and it become larger the neomorphism is called
aggrading neomorphism
neomorhic sparry calcite and can be recognized where neomorphism is incomplete because patches of dusty micrite and microspar remain can often be inferred because grains formerly supported by mud matrix are separated and seem to flot unsupported in sparry calcite
psudospar
formed during sea level high stands such as ordovician-devonian and jurqssic cret and precmabrian
dolomite
examples of large evapotrite sequences deposited in shallow subsideing cratonuc basins
paleozoic williston basin centered in north dakota and silurian mcihigan
large evaporites deosited in foreland basins
silurian salina group of new york
pennsylvanian in the taconic foreland basin
pennsylvanian-permian paradox group in the foreland basin of the ancestral rocky mountains
deposited in rift basin
hulf coast basin
proto atlantic ocean basin of jurassic to cretaceous age
deposited in deep basins assoc with the irregular closing of ocean basins at convergent plate boundaries
permian delaware basin in west texas
BIF range in 3.8-1.8 with a peak abindance between?
2.5-2.2 Ga
when did BIF hiatus?
1.0 Ga
BIF late proterozoic rocks formed from
0.8-5.5 Ga
dominate archean iron rich sed rocks fromed bwteen 3.8-2.6 Ga occur as fairly thin <10-100m elongate lenses of linited lateral extent occur within archean greenstone belts assoc with submarine ultramafic mafiic volcanic rocks mudrocks and sparse volcanoclastic greywacke sandstonesform in dee water marine forearc or backarc basin or advanced intracratonic rift settings minimal influx of detrital sediments
algoma type BIF ontario california
iron rich bands are composed almost exclusively extremely fine grained rocks
femicrites
dominate proterozoic iron rich sed rocks 2.6-1.8 Ga and again from 0.8-0.5 Gamuch larger than algoma 100-1000m occur in borad belts contain fermicrites and GRANULAR IRON FORMATIONS with ooids pisoliths intraclasts and pelltes similar to those in shallow water carbonate sequences
superior type BIF
the slope of the stress – strain line is referred s a constant of proportionality that
describes the slope of the line. The slope
steepness of line E is a measure of resistance
to elastic distortion. The E slope is dependent
upon the stiffness or rigidity of the material.
A rigid, stiff rock (high E) such as granite
requires greater stress to achieve a given strain
than a soft, pliable shale (low E
Young ’ s modulus of elasticity (
which mesoscopic
ductile behavior is facilitated by microscopic fracturing and frictional sliding.
Cataclastic fl ow occurs at low lithostatic
pressures in the shallow crust.
Cataclastic fl ow
high pressure diffusional mass transfer process grain boundaries are compressed and dissolved resulting in the generation of a fl uid
phase (Figure 16.14 ). As each mineral
has different dissolution tendencies,
pressure solution results in mineral
differentiation whereby more soluble
minerals are removed and less soluble
minerals are concentrated can involve substantial
volume loss and is particularly important in marble, metaquartzite, slate,
limestone, dolostone, shale and quartz
sandstone.
clay - rich rocks produces cleavage in
slates, as well as embayed grains and grain overgrowths in quartz - rich rocks
such as sandstone and metaquartzite.
Pressure solution
also known as
grain boundary or volume diffusion is
a high temperature and high pressure
process by which solid particles experience translation within a mineral.
Crystal lattice vacancies migrate to
sites of greatest stress and atoms relocate to sites of minimal stress.
Solid state diffusion
e commonly black –due to enrichment in carbon and iron oxides –and
have the appearance of wound sutures
stitched together
which are jagged seams
of insoluble mineral residue that accumulate and concentrate along a dissolution seam
Stylolite
common in calcite
and feldspar minerals.
Mechanical twinning
common
in micas and other platy minerals such as
clays.
Kinking
ability to fl ow at
shallow depths results in unusual qualities
that make rock salt highly suitable for the
storage of oil as part of the strategic petroleum reserve of the US government
uitable rock for a nuclear waste repository
Rock salt ’ s ability to fl ow
p crustal and mantle processes
within Earth. Factors such as depth, temperature, stress conditions, mineral composition,
rock texture, rock competency and strain rate
rheology
refers to the rate
at which a rock is pulled apart, compressed
or sheared
Strain rate
are useful geothermometers because these
common minerals change strain behavior
with increasing temperatures
minerals such as quartz,
feldspars, amphiboles, garnet and biotite
Approximate temperatures at which
some major minerals change from brittle to
ductile behavior
Biotite ∼ 250 ° C
Quartz ∼ 300 ° C
Feldspar ∼ 400 ° C
Amphibole ∼ 650 – 700 ° C
Garnet 600 – 800 ° C
s produce undulose
extinction, deformation lamellae and recrystallization
Ductile processes
describes the resistance of rocks to fl ow. Rocks that fl ow easily
are less competent, or incompetent.
competency increases with higher pressure
but decreases with higher temperature
Competency
rocks commonly display
ductile behavior and include rock salt,
shale, siltstone, slate, phyllite and schist.
These rocks contain clays, micas, evaporates, talc, chlorite and other relatively
soft minerals with Mohr ’ s hardness < 3.
Incompetent
ocks commonly display
brittle behavior and include metaquartzite, granite, gneiss, quartz sandstone,
basalt, gabbro and diorite. These rocks
contain minerals with Mohr ’ s hardness > 3
such as quartz, feldspars and ferromagnesian minerals.
Competent
The rupture of competent layers produces “ French bread ”or
sausage - shaped structures called
are isolated remnants of competent rock that once formed a
continuous bed surrounded by less competent rocks
boudins
r commonly occurs at depths
less than 10 km because of upper crustal low
temperature/low lithostatic pressure conditions, which allows for the development of
fractures
Brittle behavior
e fractures through which fl uids fl ow,
producing one or more secondary minerals
that precipitate from solution. Common secondary vein minerals include quartz, calcite,
zeolite and chlorite
originate due to tensile or shear stresses.
Veins
produced by high strain rate
events that blast rock apart due to high pressures. Igneous intrusions with high volatile
contents are capable of hydrofracturing rock
producing random breakage. Rare meteorite
impacts are also high strain events that
produce massive disruption of rock. High
strain rates can produce stockwork veins,
which are a cluster of irregularly shaped veins
of variable orientation that occur in a pervasively fractured rock body
Non - systematic vein arrays
onsist of veins that
display orientations suggesting a common
origin in response to directed stress
metaquartzite beds bounded by phyllite layers. In response
to nearly vertical compressive stress, the
metaquartzite experiences horizontal tension,
resulting in brittle fracturing and the generation of extensional joints. Quartz fl uids precipitate in the joints creating tension veins
parallel to the maximum compressive stress
direction.
Systematic vein arrays
a series of offset, parallel veins that formed in response to sinistral shear within
metaquartzite.
en echelon quartz vein array
minerals are equant and may
display euhedral crystal faces indicating
growth within an unimpeded open space
Blocky or sparry
displays a linear, acicular
character (Figure 16.26 ) suggesting that vein
growth was incremental in response to fracture width increase
develop by
repeated cycles of a “ crack and seal ”mechanism whereby elevated fl uid pore pressures
crack a vein, followed by sealing from mineralized solution
provides information regarding displacement sense as well
as progressive vein growth in both brittle and
ductile environments.
Fibrous veins
an imaginary plane connecting
a series of hinge lines
axial surface
(axial plane)
the point at which the sense of curvature
changes from one fold to another
inflection point
a convex - upward structure are called
antiforms
concave - upward shapes are referred
s synforms
consist of two limbs that dip
towards the hinge. Synclines contain
young rock in the hinge and progressively
older rock away from the hinge
Synclines
consist of two limbs that
dip away from the hinge. Anticlines
contain old rocks in the hinge and progressively younger rock further away from
the hinge.
Anticlines
younger fold
structures are superimposed upon earlier fold
structures, refolded folds are referred to as
superposed folds or superimposed folds
consist of folds in which
the limbs and hinges have been pulled apart
due to extension (
occur with multiple fold generations,
involving the replacement of an earlier tectonic fabric (S 1) by a more recent tectonic
fabric (S 2) by ductile mechanisms such as
recrystallization and pressure solution.
e associated with high temperature and high pressure metamorphism
Transposed folds
be used in the analysis of a map - scale antiform. Geologists can determine position
within a map - scale fold structure by looking
down the plunge direction of the
parasitic
folds.
essentially ductile fault zones
that accommodate displacement
develop in ductile lower crustal rocks.
commonly occur in
tectonic m é langes mylonites
and pseudotachylites
Shear z ones
consists of larger rock blocks encased within
a scaly, clay - rich matrix.
. M é lange
also known
as texture, refers to the geometric arrangement of grains within a rock.
fabric
Parasitic folds produce
Z
(clockwise rotation), M (symmetrical form)
or S (counterclockwise rotation) shapes
indicating shear sense.
produced by deformation processes after the initial lithifi cation of the
rock. Metamorphic rocks are dominated
by tectonic fabrics although some primary fabrics
tectonic
fabric
no undeformed
parts of the rock remain
continuous fabric
both
deformed and undeformed parts of the
rock are visible.
spaced
fabric
sheet - like structures that
include joints, veins, faults, axial surfaces of
folds, shear zones and cleavage
Planar features
commonly develops in
response to compressive stresses associated
with dynamic or dynamothermal metamorphism.
celavage
consists of parallel foliations oriented nearly
perpendicular to the maximum compressive
stress, and converging towards the inner arc
of the fold hinge area. is steeper than the
bedding angle in upright folds.
Axial planar cleavage
contain one long axis and
two short axes, producing needle - like structures. intersection
lineations, form lineations, crenulation lineations, stretching lineations and surface or slip
lineations
Linear structures contain one long axis and
two short axes, p
commonly forms due to the intersection of
two fracture sets or a fracture set and bedding are ∼ 5 – 10 cm long and generally less than 2 cm in width and height s facilitated by the internal
alignment of inequant clay minerals. e develops in weakly deformed shales
or mudstone and is an early stage in the development of slaty cleavage
Pencil cleavage
inear features produced by geological structures.
Form lineations
linear features
that occur as a result of a secondary cleavage
imposed upon a fi ne - grained rock (slate or
phyllite) that experienced an earlier cleavage
represent hinge lines formed by the intersection of
two planar surfaces
Crenulation lineations
refer to vein mineral
fi bers that precipitate on rock surfaces via
crack – seal processes.
Slickenlines produced during displacement in
faults and shear zones (
Slip or fi ber lineations
derived
from igneous rocks include volcanic fl ow contacts, intrusive contacts, vesicles, phenocrysts
and other features that survive the temperatures and pressures of metamorphism.
Relict features
disc - shaped (pancake or
paper - like) grains in which one axis is
signifi cantly shorter than the other
two axes
Tabular,
(prismatic) grains in which one
axis is signifi cantly longer than the other two axes, which are not equal to
one another.
Bladed
prolate (cigar -
shaped) grains in which one axis is
signifi cantly longer than the other two
axes, which are of equal length.
Acicular (needle - like)
large relict grains from
the protolith that have experienced deformation but have retained their original composition. Their large size relative to surrounding
minerals is due to signifi cant crushing or
stretching of the surrounding minerals and/or
the growth of new, smaller crystals.
minerals include quartz and
feldspars
Porphyroclasts
composed of quartz.
flaser
large grains that have
experienced neocrystallization and growth in
response to favorable temperature and pressure conditions during metamorphism
minerals include garnet, staurolite and cordierite
Porphyroblasts
occurs when inequant grains are oriented
sub - parallel to one another and can produce
lineations and foliations
Preferred grain orientation
line -
like features similar to pencils all pointing in
a common direction. Preferred orientation
of tabular grains, especially phyllosilicate
minerals, with sub - parallel long axes produces foliations.
Lineations
exist between weakly foliated
and non - foliated textures.
Gradations
a fi ne - grained ( < 1.0 mm
diameter), non - foliated fabric that develops
by contact metamorphism, producing a rock
derived from fi ne - grained protolith rocks such
as shale, mudstone, tuff or basalt
equant
edvelops in metamorphic aureoles, adjacent to igneous intrusions.
Hornfelsic texture
. Recrystallization causes hornfels to be somewhat
harder and more brittle than the mudstone
characterized by
large ( > 1.0 mm diameter) equant grains or
large inequant crystals that lack preferred orientation
occur in high grade rocks known as granulites, that form at elevated temperature and
pressure conditions associated with deep
burial.
develop during
metamorphism of a wide range of protoliths
under uniform stress conditions
display anhedral, sutured boundaries that refl ect a combination of pressure solution, recrystallization
and annealing
characterizes many non -
foliated rocks such as metaquartzite and
marble and contact metamorphosed skarn
deposits
commonly develop with minerals such as
quartz, feldspar and calcite that have low
euhedral form potentia
Granoblastic textures
contain >90% quartz and are
derived from quartz - rich sandstone or chert
protoliths Because the quartz
grains interlock, rupture occurs through grains, rather than around grain boundaries gives this mineral a smooth, glazed
appearance as opposed to the granular appearance
Metaquartzites
granoblastic metamorphic rocks
rich in calcite and/or dolomite via dynamothermal,
deep burial or contact metamorphism. accessory
minerals include graphite and calcium -and/
or magnesium - bearing minerals such as
brucite, diopside, forsterite, wollastonite epidote, serpentine, idocrase (vesuvianite),
tremolite and grossular garnet. Accessory
minerals provide distinctive hues that allow
marble to assume a wide variety of colors Venus de Milo and Michelangelo ’ s
David, sculptured from Gre
Marble
also known as tactites, are granoblastic calc - silicate rocks formed by contact metamorphism of carbonate country rocks such
as limestone or dolostone. The release of silica
and volatiles from the magma results in extensive metasomatism, generating calc - silicate
mineral assemblages and/or metallic ore
deposits contain carbonate
minerals such as calcite, dolomite and ankerite and silica group minerals such as
quartz minerals
(calcium – magnesium silicates) include wollastonite, tremolite, diopside, talc, epidote,
grossular garnet, phlogopite and idocrase
(vesuvianite
associated ore minerals such as
gold, silver, tungsten, molybdenum or iron.
Skarn
develop during dynamic metamorphism in a
wide variety of rocks within 15 km of Earth ’ s
surface
Cataclastic texture
Cataclastic rocks that lack cohesion are
breccia if they contain coarse ( > 2 mm diameter), angular fragment
if they are
composed of fi ner sized fragments.
gouge
develop during dynamic or
dynamothermal metamorphism develop during dynamic or
dynamothermal metamorphism
Metabreccias
cohesive rocks with cataclastic textures produced by brittle deformation form under low temperature,
high strain, dynamic metamorphic conditions
such as upper crustal fault zones. non - foliated; but phyllosilicate rich can be
cataclasites
are glassy rocks produced by
high strain rates generating localized melting
in fault zones Near instantaneous solidifi cation of melts produced by pressure release during fracturing produces very
dark - colored, vitreous to fl inty rocks commonly occur as vein material in
cataclastic rocks such as fault breccias and
cataclasites.
Pseudotachylites
Cataclasite series rock terms
10 – 50 Protocataclasite
50 – 90 Cataclasite
90 – 100 Ultracataclasite
Glassy spherules called t form
as rocks are locally melted due to impact.
The impact of extraterrestrial rock bodies
produces showers of droplets that cool
very rapidly as
tektites
high pressure mineral coesite was fi rst discovered in the fi eld at
Meteor Crater
can occur with
non - foliated or foliated textures
metaconglomerates, serpentinites, soapstones, greenstones, granulites,
eclogites and amphibolites
derived from conglomerate protoliths and contain sub - rounded
to rounded relict clasts with diameters > 2 mm
metaconglomerates
form by the metamorphism of
conglomerates and/or breccias in response to
strong non - uniform stress during dynamothermal or dynamic metamorphism. During
metamorphism, pebbles and cobbles are
shortened and/or fl attened parallel to the
Z - strain direction and relatively elongated
parallel to the X - strain direction Pebble alignment may defi ne a metamorphic foliation or lineation fabric examples of lineations occur in Pennsylvanian
Purgatory Formation metaconglomerate in
the Narraganset Basin, Rhode Island where stretched pebbles are arranged parallel
to one another like loaves of French bread
Stretched pebble metaconglomerates
forms by hydrothermal
alteration of ultrabasic rocks at temperatures
below ∼ 500 ° C group minerals (Chapter 5 ) include lizardite
[Mg 3 Si 2 O 5 (OH) 4], chrysotile [Mg 3 Si 2 O 5 (OH) 4 ]
and antigorite [(Mg,Fe) 3 Si 2 O 5 (OH) 4]. Lizardite and chrysotile are low temperature minerals and antigorite is the higher temperature
mineral.
Serpentinites
fi ne - grained rocks that form
through the alteration of ultrabasic rocks, or
magnesium - rich sedimentary rocks such as
dolostone, by low temperature and low pressure hydrothermal fl uids These minerals impart a low hardness and
white to green color low porosity prevents
staining or seepage
Soapstone
green - colored rocks rich in
silicate minerals that commonly include chlorite, epidote, prehnite, pumpellyite, talc, serpentine, actinolite and albite. orm by low to moderate (200 – 500 ° C) temperature alteration of basic and, to a lesser
extent, ultrabasic igneous rocks. During metamorphism, plagioclase and primary ferromagnesian silicates such as olivine, pyroxene
and amphibole are converted into this miberal commonly produced by hydrothermal metamorphism of basalts and gabbros in oceanic
crust near divergent plate boundaries later be incorporated
into m é langes and orogenic belts along convergent plate boundaries occur on a very large
scale in greenstone belts, which are abundant
in Precambrian rocks
Greenstones
(sodium - rich basalt) that occrus in greenstones
spilites
(sodium - rich andesite) that occrus in greenstones
keratophyres
occur in large synclinal structures ultrabasic
metavolcanic rocks ( komatiites) and metabasalt form the basal layers and are overlain
successively by intermediate and silicic metavolcanic and metavolcaniclastic sequences,
which are in turn capped by graywackes and
chert commonly parallel
granulite belts containing rocks of granitic to
dioritic composition metamorphosed at high
temperatures and pressures yield valuable metallic ore deposits containing
copper, gold, silver, nickel, zinc and lead
Greenstone belts Phanerozoic greenstone belts are rare. best known greenstone localities include the Barberton belt
in South Africa, the eastern goldfi elds of
Western Australia, the Superior and Slave
Provinces in North America, and the Sao
Francisco Craton in Brazil.
dominate the history of continents in the Archean and Early Proterozoic Eons green - colored minerals such as actinolite, chlorite, epidote, prehnite, pumpellyite, serpentine and talc. belts are synclinal to tabular rock assemblages that contain peridotite and gabbroic
intrusive rocks and ultrabasic to basic volcanic rocks called komatiites. occur in association with granitic gneisses in Precambrian cratons
Greenstone belts
formed by extensive metasomatic alteration of basic and ultrabasic rocks through chemical reactions with H 2O and CO 2
actinolite, chlorite, epidote, prehnite, pumpellyite, serpentine and talc
overlain successively by basalt and rhyolite layers.
Komatiites
Amphibolites derived from
basic igneous rocks such as basalt and gabbro
are called
ortho - amphibolites
s amphibolites produced from sedimentary protoliths
are called p
para - amphibolites
are medium -to coarse - grained
rocks that contain granoblastic to foliated
texture by high temperature
( > 800 ° C) and high pressure ( > 10 kbar; ∼ 33 km
depth) metamorphism
High temperature: s trigger dehydration reactions resulting in the transformation of
hydrous amphibole and mica minerals into
anhydrous minerals such as pyroxene, potassium feldspar, kyanite and garnet. The high
pressure and very low water content prevents
melting, and preserves the rock ’ s metamorphic fabric
Saxony, Germany minerals include orthopyroxene, clinopyroxene, potassium plagioclase, garnet and
quartz.
orm in high temperature
and high pressure conditions of the lower
continental crust, upper mantle and as a result
of subduction of crust at convergent margins. common in Precambrian greenstone belts and in association with
eclogites.
Granulites
s are very high pressure, high temperature rocks that develop principally from
basalt/gabbro protoliths
major rock type in Earth ’ s lower crust because
they are stable at temperatures that exceed
400 ° C and pressures that exceed 1.2 GPa
commonly red
and green because they contain green jadeite
pyroxene, omphacite (sodium/calcium pyroxene) and red garnet as major minerals. can form by a number of processes, which include (1) high pressure recrystallization of deep continental crustal rocks
during thickening at continent – continent collisions, (2) partial melting of the mantle
followed by deep crystallization as high pressure eclogite, or (3) high pressure metamorphism of subducted oceanic lithosphere deep
within Earth
high density
(3.5 – 4.0 g/cm 3
) may be one of the driving
forces for plate motion. The slab - pull effect
generated by
eclogite
fi ne - grained, aluminum - rich, pelitic
rocks that possess fl at, planar cleavage. layering is defi ned by the sub - parallel orientation of microscopic phyllosilicate mineral
grain develops during
metamorphism under non - uniform stress at
relatively low temperatures ( ∼ 150 – 250 ° C)
and low pressures
Slate
haracterized by larger crystals and more wavy surfaces
than slaty cleavage silky or glossy sheen commonly develop by the recrystallization of slate and therefore from the same
protoliths as slate
t temperatures of ∼ 250 300 ° C, smectite and illite clays metamorphose
to slightly coarser grained minerals such as
sericite, muscovite, talc and chlorite that align
parallel to each other and defi ne foliations.
develops
in response to non - uniform stresses at temperatures and pressures that exceed those that
produce slaty cleavage display
a crenulation cleavage that cross - cuts an
earlier generation of cleavage
Phyllites
very common foliation defi ned by the sub - parallel arrangement
of macroscopic platy minerals such as phyllosilicates in closely spaced metamorphic
layers. This foliation is commonly less regular
than that of either slates or phyllites. Light -
refl ecting, macroscopic crystals generally
impart a high sheen or sparkle to the like slates and phyllites,
can develop from pelitic (shale, mudstone,
graywacke) or altered tuff protoliths produced by dynamothermal
metamorphism at convergent plate boundaries with temperatures > 300 ° C
schist or schistosity
alternating light - colored quartz and/or feldspar - rich layers and dark - colored layers rich
in biotite, amphibole and –at increasing temperatures –pyroxenes. develop from lower grade metamorphic rocks as well as from a variety of
protoliths including granites, diorites, gabbros,
mudrocks, tuffs and graywackes. The protolith dictates the mineral components in gnei evelop due to extensive
layer transposition, recrystallization and
neocrystallization processes that result in the
segregation of minerals into separate layers
Gneisses form in dynamothermal settings
at temperatures that commonly exceed
∼ 600 ° C
Gneiss
Gneisses that develop from an
igneous protoliths are called
orthogneiss
The vast majority of gneissic bands originate by results from the pulling apart of earlier
folded layers resulting in the separation of
hinges and limbs
Transposition
which refers to the
thin, sill - like intrusion of magma into parallel country rock layers occur to a limited extent when
granitic magma intrudes mafi c country
rock producing alternating light and dark
color bands.
“ Lit par lit intrusion
possess textural and structural characteristics of both igneous and metamorphic roc
commonly display an
irregular, swirling mix of colors
contain zones of rock with the
outward appearance of granitoid igneous
rocks mixed with zones of rock that resemble
typical gneiss. Light - colored segments consist
of quartz and feldspars; dark - colored components are enriched in pyroxene. With additional melting, migmatites melt suffi ciently so
as to produce magma. under high temperature ( > 800 ° C) conditions in the lower crust dynamothermal metamorphism at convergent plate boundaries by a
number of processes that involve some combination of (1) partial melting (anatexis),
(2) magma injection, and/or (3) ductile deformation and plastic fl ow of rocks in the lower
crust.
Migmatite
silica -and iron - rich rocks that formed
primarily in the Early Proterozoic and
Archean
alternating
hematite, magnetite and chert layers form red
and black color band
Deposits in the Lake Superior region
of North America and in Western Australia
are among the riches this deposit
Ironstone
Mylonite series as defi ned by Sibson
10 – 50 Protomylonite
50 – 90 Mylonite
90 – 100 Ultramylonite
metaquartzites that contain
20 – 30% iron and are also commonly banded.
Ironstones have been major sources of iron
ore since the mid 1800s considered waste rocks because of their lower
iron content, are now the principal ore rocks
mined in the Lake Superior region due to
depletion of richer ore deposits.
Taconites
provide important information
regarding the sense of displacement in shear
zones
Mylonites
are pervasively
deformed rocks so that their original composition and texture are largely obliterated defi ned by their solid state fl ow
fabric generated through intense ductile or
brittle – ductile deformation
Tectonite
Foliated tectonites are called
S tectonites.
s. Tectonites with
a pronounced lineation, but no foliation, are
called
L tectonites.
Tectonites with both foliation and a lineation are referred to a
L - S
tectonites
s indicate the sense of displacement in shear zones and may also provide
information on displacement distance. Linear
features (e.g., fold axes) cut by planar faults
or shear zones provide “ piercing points
Offset marker
re asymmetrical porphyroclasts or poryphyroblasts with mineral
tails that “ point ”in the direction of shear.
Tail complexes form commonly about minerals such as feldspars and quartz well
developed in schists, gneisses and mylonitic
rocks
Grain t ail c omplexes
consist of
wedge - shaped tails that do not cross the reference plane of shear
Sigma ( σ) grain tail complexes c
are produced by relatively rapid grain rotation relative to tail growth rate. Rapid grain
rotation results in a signifi cant bending of the
earlier formed parts of the tail so that it
crosses the reference plane.
Delta ( δ) grain tail complexes
preferentially oriented in the
direction of shear. The fractures are inclined
at low angles ( < 45 ° ) to foliations. show displacement consistent with
the overall sense of shear
Synthetic
fractures
are preferentially oriented in
a direction opposite to the sense of shear.
Antithetic fractures are inclined at high angles
( > 45 ° ) to the foliation plane and display an
opposite sense of movement to overall sense
of shear
Antithetic fractures
develop in mylonitic, schistose
and gneissic rocks subjected to ductile shear.
S - C foliations
e letter S represents schistosity (foliation)
and the letter C is for “ cisaillement ” , a French
term for shear direction, which lies in the C
plane
phyllosilicates form the
schistosity and dissolution seams occur within
the cisaillment zone
low temperature
e ( ∼ 150 – 400 ° C),
moderate temperature
(400 – 600 ° C)
high temperature
( > 600 ° C) conditions
atmospheric pressure ranges
low pressure (0 – 2 kbar ≈ 0 – 6 km depth),
moderate pressure (2 – 6 kbar) or high
pressure ( > 6 kbar ≈ > 20 km depth)
into the second half of the 20th century,
metamorphic petrologists considered the
highest metamorphic pressures to be
∼ 15 kbar
3.3 kbar corresponds to
∼ 10 km
ultra - high
pressure xenoliths are derived from depth
400 km
minerals form within a more limited temperature and/or pressure range. These minerals,
referred to rovide critical
information because they effectively indicate
the temperature/pressure conditions of metamorphism.
index minerals,
lines drawn on
geological maps that mark the fi rst appearance of a particular index mineral.
chlorite isograd marks the fi rst
appearance of chlorite and the biotite isograd
marks the fi rst appearance of biotite.
e consists of the region
bounded by two isograd lines
metamorphic zone
biotite isograd marks the
transition to the higher grade biotite zone
six metamorphic zones based on
the six index mineral isograds are progressive metamorphism whereby progressively higher grades of
metamorphic minerals and rocks are produced with increasing temperature in an
evolving orogenic belt
Barrovian zones
bounded by the chlorite
and biotite isograds chlorite - bearing slate, chlorite - sericite phyllite
and chlorite - sericite schist. quartz,
muscovite, albite (sodium plagioclase) and
pyrophyllitebecomes unstable and
begins to be replaced by biotite at the high
temperature limit of this zone
chlorite zone
marking the fi rst appearance of
biotite –and the almandine (garnet) isograd.
Common rocks in the biotite zone include
sericite - biotite phyllite and biotite schist. forms
by chemical reactions that involve minerals
such as chlorite, muscovite, quartz, magnetite
and rutile
Biotite z one
is bounded by the almandine garnet isograd –marking the fi rst appearance of almandine garnet –and the staurolite
isograd include garnet schist or garnet - mica
schist Other minerals common in pelitic
rocks of the almandine zone include biotite,
muscovite, magnetite, quartz and sodium plagioclase minerals such as albite or oligoclase
forms through the chemical transformation of chlorite and magnetite
almandine zone
lies between the staurolite
isograd –marking the fi rst appearance of the
higher temperature mineral staurolite –and
the kyanite isograd quartz,
almandine, potassium feldspar, biotite and
muscovite. Potassium feldspar forms through
the breakdown of muscovite staurolite exists only
within the staurolite zone
Staurolite z one
occurs between the kyanite
and sillimanite isograds that mark the fi rst
appearances of kyanite and sillimanite, Common rock types include
kyanite schist and kyanite - mica schist commonly occurring in pelitic rocks
of the kyanite zone include biotite, muscovite, almandine garnet, cordierite and quartz.
Kyanite z one
occurs inside the sillimanite isograd and marks the highest temperature zone sillimanite schist, sillimanite gneiss and
cordierite gneiss e biotite, muscovite, cordierite,
quartz, oligoclase and orthoclase. Sillimanite
and potassium feldspar can also develop by
dehydration of muscovite in the presence of
quartz, as in the reaction
Sillimanite z one
introduced the concept of
metamorphic facies –a more comprehensive
approach to assessing the conditionsrecorded
by metamorphic rocks . Metamorphic facies
are defi ned by a group or assemblage of critical minerals, rather than a single index mineral
as used for Barrovian zones
Eskola
)initially identifi ed fi ve metamorphic
facies
sanidinite, hornfels, greenschist, amphibolite and eclogite.
original hornfels facies
proposed by Eskola
: (1) albite - epidote hornfels, (2) hornblende hornfels, (3) pyroxene hornfels, and
(4) sanidinite hornfels
Chlorite, muscovite, quartz,
pyrophyllite, albite, graphite Calcite, albite, biotite,
zoisite, quartz
Chlorite, albite, epidote,
sphene, calcite, actinolit
Chlorite
Biotite, muscovite, chlorite, quartz
Biotite
Almandine, biotite, magnetite,
muscovite, quartz
Garnet, andesine,
zoisite, biotite
Almandine
Sillimanite Sillimanite, biotite, cordierite,
muscovite, almandine, quartz,
oligoclase, orthoclase
Bytownite, anorthite,
diopside, garnet
Sillimanite
include non - foliated, fi ne -
grained hornfels rocks and coarser grained
rocks with granoblastic textures heat - induced metamorphism in
aureoles surrounding igneous intrusions. T metamorphic aureoles are localized around
the intrusion, commonly having widths of
100 m or less. Ocean spreading centers represent regionally extensive zones of hydrothermal metamorphism that produce hornfels
facies rocks on a large scale, effectively altering entire ocean basins.
Hornfels facies
Chloritoid, albite, epidote, muscovite, chlorite, biotite,
andalusite, quartz
Hornfels
Pelitic
Epidote, albite, chlorite, actinolite, biotite, talc, sphene Hornfels
Basic
Antigorite (serpentine), actinolite, tremolite, talc, chlorite,
biotite, albite, magnesite, brucite, dolomite
Hornfels
Ultrabasic
Albite, epidote, quartz, microcline, muscovite, biotite Hornfels, metaquartzite
Quartz - feldspathic
Calcite, dolomite, epidote, tremolite, idocrase (vesuvianite),
magnesite, brucite
Marble, skarn
Calcareous
low temperature hornfels facies,
with temperatures generally < 450 ° C and pressures < 2 kbar (depth < 6 km). develop in the outer fringes
of many metamorphic aureoles. The characteristic minerals of this assemblage are albite
and epidote, which most commonly occur in
basaltic tuffs and lavas thermally metamorphosed at ocean ridges, hotspots and in volcanic – magmatic arcs roughly the low pressure
equivalent of the greenschist facies
Albite - e pidote h ornfels f acies
compose the bulk of many metamorphic aureoles, forming at temperatures generally between 450 and 600 ° C and at pressures < 2.5 kbar ( < 8 km). Chlorite, albite,
epidote and actinolite –common in albite -
epidote hornfels facies –are notable by their
absence in the hornblende hornfels assemblage. At temperatures above 450 ° C, dolomite is replaced by diopside via the following
chemical reaction low pressure equivalent of the amphibolite facies,
Hornblende h ornfels facies
less common than the lower temperature hornfels facies commonly adjacent to higher temperature basic intrusions, pyroxene hornfels
facies rocks evelop at temperatures of 600 – 800 ° C and at pressures < 2.5 kbar
( < 8 km). the higher temperatures at which pyroxene
hornfels form, dehydration reactions produce
a largely anhydrous suite of minerals
Pyroxene h ornfels f acies
are very rare, forming in very high temperature ( > 800 ° C) and low pressure ( < 2.5 kbar ≈
< 8 km) conditions in association with basic
and ultrabasic intrusions
develop where the country rock is in contact
with the intrusion or in country rock inclusions (xenoliths) within the intrusion
Contact metamorphic facies
provide a means to place hydrothermal metamorphic rocks and ocean ridge alterations
into the facies concept
Sanidinite hornfels facies
as a low grade metamorphic
facies produced by temperatures between
∼150 and 300 ° C and pressures less than
5 kbar ( ∼ 15 km depth)
hydrous sodium and
calcium aluminum tectosilicate mineral group
formed by diagenetic or low temperature
metamorphic reactions
coexist with quartz, include analcime, laumontite, heulandite and wairakite.
Accessory minerals in the zeolite facies may
include albite, kaolinite, vermiculite, adularia,
pumpellyite, sphene, epidote, prehnite,
montmorillonite, smectite, muscovite, chlorite
and calcite
originate from the
hydrothermal alteration of volcanic protoliths
such as basalt and andesite, the devitrifi cation
of basaltic glass and tuff, and the reaction of
pelites and graywackes with saline waters
occur in isolated vesicles and
veins or as pervasively disseminated minerals
within the metamorphic rock.
develops by
hydrothermal alteration at divergent margins,
hotspots and convergent margins or during
burial metamorphism at depths less than
5 km. Laumontite and heulandite are particularly common peratures approaching 250 ° C and depths of
3 – 5 km, zeolite facies minerals begin to alter
to prehnite and pumpellyite facies minerals,
which occur in the upper zeolite facies but are
the dominant minerals in the prehnite -
pumpellyite facies, discussed below
Zeolite facies
Kaolinite, zeolite, quartz, montmorillonite,
vermiculite, phengite, epidote, muscovite
Metapelite, argillite, slate
Pelitic
Zeolite, albite, quartz, phengite, sphene, epidote,
chlorite, prehnite, pumpellyite
Metabasite or greenstone
Basic
Lizardite serpentine, talc, olivine, chlorite, prehnite,
pumpellyite
Serpentinite or greenstone
Ultrabasic
Quartz, zeolite, albite, sphene, epidote, quartz,
muscovite
Metaquartzite or metagraywacke
Quartz - feldspathic
Zeolite, calcite, quartz, epidote, dolomite, lawsonite,
talc, muscovite
Marble
Calcareous
zeolite minerals
natrolite
stilbite
chabazite
heulandite
thompsonite
analcime
laumonite
wairakite
produced by hydrothermal alteration and burial
metamorphism at temperatures and pressures
that exceed zeolite facies conditions.
based on metasedimentary basin deposits in New Zealand.
widespread at oceanic ridges and therefore affect
substantial portions of the oceanic crust
generated at spreading ridges
protoliths include basalt, graywackes and mudstones
(pelites). generally
forms under low temperature (250 – 350 ° C)
and fairly low pressure ( < 6 kbar, ∼ 20 km
depth) conditions minerals
include quartz, albite, chlorite, muscovite,
illite, phengite, smectite, sphene, titanite,
epidote, lawsonite and stilpnomelane.
prehnite - pumpellyite facies
higher temperature assemblage
containing pumpellyite and actinolite has
been called
transitional pumpellyite -
actinolite facies
generally form under medium temperature (350 –
550 ° C) and pressure (3 – 10 kbar ≈ 10 – 30 km
depth) conditions associated with dynamothermal metamorphism at convergent plate
boundaries. At these higher temperature and
pressure conditions, pervasive recrystallization and/or neocrystallization commonly
results in the obliteration of relict text
epidote, chlorite and actinolite
abundant in
orogenic fold and thrust belts, where they
record regional, moderate temperature/pressure metamorphic conditions at convergent
plate boundaries. extensively exposed in orogenic
belts such as the Appalachians, the Alps and
the Otago fold and thrust belt of southern
New Zealand.
Greenschist f acies
orresponds to lower
greenschist facies conditions with minerals such as chlorite, dolomite, stilpnomelane and calcite.
chlorite zone
corresponds to upper
greenschist facies conditions and contains
biotite and tremolit
biotite zone
corresponds to the uppermost greenschist to epidote - amphibolite facies
lower part of the almandine garnet
As pressures decrease, the low pressure
fi eld of greenschist metamorphism grades into
the
albite - epidote hornfels facies
As progressively higher temperature conditions develop
within orogenic belts, the greenschist facies
transforms into higher grade
amphibolite
facies metamorphism
form at high temperatures ( ∼ 550 – 750 ° C) and moderate to high pressures (4 – 12 kbar ≈ 12 – 40 km depth) in regional orogenic belts at
convergent margins marks the appearance of
staurolite in pelitic rocks, where staurolite
may occur with kyanite. increasing temperature, include the upper part of the almandine
zone, all of the staurolite and the lower part
of the sillimanite zone.
Amphibolite f acies
transition from greenschist to amphibolite facies is
marked by an increase in hornblende, garnet
and anthophyllite and a decrease in actinolite,
chlorite, biotite and talc in basic and ultrabasic rocks.
Barrovian zones Almandine Staurolite Sillimanite
Mineral species
Albite
Albite-oligoclase
Oligoclase-andesine
Andesine
Epidote
Actinolite
Hornblende
Chlorite
Metabasite
Chlorite
Muscovite
Biotite
Almandine
Staurolite
Andalusite
Sillimanite
Plagioclase
Quartz
Metapelite
The low temperature
part of the amphibolite facies that corresponds with the almandine zone is also known
as the
epidote - amphibolite facies ( “ transitional ”facies)
With decreasing pressure, the lowest pressure
fi eld of the amphibolite facies metamorphism
grades into
hornblende hornfels fi eld
As
temperatures increase, the amphibolite facies
grades into the higher temperature
granulite
facies
consists
of high temperature ( ∼ 700 – 900 ° C) and moderate to high pressure (3 – 15 kbar ≈ 10 – 50 km
depth) mineral assemblages minerals are predominantly anhydrous (Table 18.11 ), due to
dehydration reactions at high temperatures.
Hydrous minerals hornblende and biotite, but not muscovite,
granulite facies
Foliated granulite rocks are
less common because many of the inequant,
hydrous phyllosilicate minerals
Hydrous minerals hornblende and biotite,
but not muscovite, can occur in the lower
part of the granulite facies, sometimes referred
granulite I
The upper part of the granulite facies, sometimes referred to as haracterized entirely by anhydrous
minerals
granulite II
Amphibole minerals (tremolite, anthophyllite, hornblende) dehydrate to
pyroxene minerals (enstatite, diopside, hypersthene), and
phyllosilicate minerals (such as muscovite)
dehydrate to anhydrous minerals (orthoclase)
in response to high temperatures.
occurs as surface waters percolate downward,
in so doing leaching near surface metals and
concentrating them at deeper levels within
Earth ’ s crust
epigenetic process that commonly develops in
oxidizing zones above the water table
Supergene enrichment
a primary or syngenetic
process that occurs as deep, upwelling magmatic fl uids concentrate ore synchronous with
rock development
Hypogene enrichmen
ore
bodies are considered to be veins or layered,
stratiform bodies. Tabular ore bodies commonly form along fracture systems, igneous
layers, metamorphic foliations or sedimentary
beds
Tabular
ore bodies, appropriately
referred to as pipes or chimneys, commonly
form in response to ore - enriched magma or
hydrothermal solutions that rise buoyantly
towards Earth ’ s surface.
Cylindrical
e. Lensoid ore deposits
are referred to as meaning that they
have a foot - like shape.
podiform
broadly
disseminated ore deposits typically develop in
close proximity to large igneous intrusions
in which ore - bearing fl uids infi ltrate –and in
many cases locally metamorphose –surrounding rock. Intense forces associated with
igneous intrusions result in elevated fl uid
pressures. These fl uid pressures are directed
outward into the rock body resulting in extensive hydrofracturing of the surrounding
country or host rock.
Irregular
(VMS) deposits
are copper – zinc – lead sulfi de deposits concentrated on the ocean fl oor at divergent and
convergent plate boundaries ores
include silver, gold, cobalt, nickel, iron, tin,
selenium, manganese, cadmium, bismuth,
germanium, gallium, indium and tellurium
upwelling plumes of black, metal -
laden “ smoke ”from ocean ridge vents release
hydrothermal fl uids. The chimney - like structures produced by > 360 ° C black smokers are
enriched in chalcopyrite, sphalerite, pyrite
and anhydrite. Metasomatic mixing of
seawater and black smoker hydrothermal
fl uids also produce “ white smokers ” , erupting
< 300 ° C plumes that precipitate quartz,
calcite, anhydrite, pyrite and barite on the sea
fl oor.
accumulate by the growth
and subsequent collapse of black smoker
chimneys resulting in layered (stratiform) or
lens - shaped (podiform) metal deposits and
collapse breccias overlying stockwork sulphide – silicate dike structure
Volcanogenic m assive s ulfi de d eposits
produce
mounds and nodules enriched in manganese,
zinc, iron, cobalt, copper and nickel. Beneath
the overlying mound, hydrothermal fl uid fl ow
and steeply inclined chemical and thermal
gradients commonly produce cylindrical pipe
zones with a higher temperature, chalcopyrite - rich inner core and lower temperature,
sphalerite – galena - rich outer zones
black smoker environments
Named after the Troodos ophiolite (Cyprus) in the Mediterranean Sea.
Cyprus - type VMS are basalt - dominated deposits associated with
ophiolites and enriched in copper, zinc, nickel, chromium and
manganese and with minor amounts of silver and gold
Cyprus type
Juvenile, nascent
volcanic arc
Besshi type
Form in ocean ridge
(East Pacifi c Rise)
or backarc basin
Cyprus type
Named after mature convergent margin deposits in the Japanese
convergent arc system. Kuroko - type VMS are dominated by silicic
rocks such as rhyolite. Kuroko deposits are enriched in copper, zinc
and lead and may also contain substantial gold and silver
Kuroko type
Named after the Besshi copper mine in Japan. Besshi - type VMS are early
formed convergent margin deposits containing basalt, rhyolite and
greywacke rocks. Besshi deposits are notable for their ore
concentrations of copper and cobalt and only minor concentrations of
zinc
Besshi type
Mature volcanic arc
or backarc basin
(Okinawa Trough)
Kuroko type
ores are
leached from their igneous host rocks and
concentrated in overlying sedimentary rocks.
Rift d eposits
most famous
example of a rift basin deposit
ron –
copper – nickel deposits represent two important rift deposits involving sedimentary
deposits bearing ore minerals derived from
underlying rift basalts.
represents a 1.1 Ga continental rift that
formed synchronous with the Grenville
Orogeny in eastern North America underlain
by the Duluth gabbro complex, which formed
from basaltic magma that crystallized at
deeper levels within Earth ’ s interior. As
magma fractures and intrudes the pre - existing
host rock, dissolved metal ions infi ltrate, cool
and precipitate via magmatic crystallization
processes or magma segregation processes.
Keweenaw Basin in the Lake Superior
region of Michigan
represent two important rift deposits involving sedimentary
deposits bearing ore minerals derived from
underlying rift basalts.
Bethlehem, Pennsylvania iron deposits
and the Keweenaw, Michigan (USA
formed
from basaltic magma that crystallized at
deeper levels within Earth ’ s interior.
s recognized as
an important platinum group element ore
deposit yet to be mined.
e Duluth gabbro complex
liquids separate from metal - rich,
silicate magma
n in silicate magma
results in the concentration of metallic sulfi de
deposits containing copper, iron, nickel, chromium, vanadium, palladium and platinum.
Common ore minerals include chalcocite,
bornite, chalcopyrite, chromite, pentlandite, nickelline, magnetite and hematite.
Immiscible s ulfi de d eposits and
l ayered i gneous i ntrusions
Exceptional
examples of ore - bearing layered igneous
intrusions include
the Sudbury Mine in
Ontario (Canada), the Duluth Complex and
Stillwater Mine in Montana (USA), the Skaergaard Intrusion of Greenland and the Bushveld Complex of South Africa
principal source of
copper –form as silica - rich magma intrudes
and fractures the host rock and subsequently
crystallizes. Forces associated with magma
injection, coupled with hydrothermal fl uid
pressures, result in the diffuse infi ltration of
ore - bearing fl uids into complex network of
fractures and pore spaces of the surrounding
rock at temperatures > 500 ° C. Cooling and
crystallization results in massive, low concentration ( <2%) deposits of copper, molybdenum, gold, zinc, mercury, silver, lead, lithium and tin disseminated throughout a zone of
alteration within the host rock and in more
concentrated veins surrounding the intrusion ccur in association with
silicic to intermediate intrusions, such as
granite or granodiorite, at convergent plate
boundaries.
Porphyry deposits
world ’ s largest open - pit porphyry
copper mine, producing 12 million tons of
copper since open - pit operations began in
1906
0.8 km deep and 4 km wide Bingham Mine in Utah (USA
Cordilleran fold belt extending from Alaska southwards through the
Andes Mountains. Similar deposits also
occur in Indonesia and throughout the
Alpine – Himalayan belt
Porphyry deposits of copper
associated with
magma intrusions due to extensional hydrofractures that develop as hydrothermal fl uids
escape upward from the magma, and later
cool and precipitate as vein deposits. Vein
deposits occur at plate boundaries as well as
intraplate settings.
Vein deposits
Because of the high concentration of metals, vein deposits are referred
to as can contain gold,
silver, copper or metal sulfi des that occur in
association with gangue minerals such as
quartz or calcite
lode deposits
Familiar examples are the lode veins
famous gold vein deposits originated as vein - fi lling fractures produced by
granitic intrusions at convergent margin
systems.
1849 California gold
rush and the Klondike gold rush of Canada
coarse - grained igneous textures that develop in plutons of granitic composition
containing quartz, feldspars, amphiboles
and micas as major minerals –occur within
continental plates and at convergent plate
boundaries important sources of
tin, molybdenum, gold and silver and the
primary source for beryllium, lithium, tantalum, niobium and rare Earth element ores
Pegmatite
deposits
promote ion diffusion and the development of large crysta
OH, fl uorine, boron and
H 2O
concentrate metallic
elements into ore deposits through solid
state changes as well as hydrothermal fl uid
reactions. Hydrothermal fl uids are critically
important in driving metamorphic reactions
and in concentrating ore metals
Metamorphic o re - f orming
e nvironments
e hydrothermally altered assemblages that contain thick
sequences of volcanic suites and interbedded
sedimentary layers
contain among the world ’ s greatest concentrations of copper, chromium, nickel, gold,
cobalt and silver deposits.
consist of down - warped basinal
deposits in which peridotite rocks are overlain
successively by basaltic layers, silicic igneous
rocks and marine sediments derived from
develop due to slow cooling of a low viscosity
magma characterized by high volatile content.
Volatiles such as OH, fl uorine, boron and
H 2O promote ion diffusion and the development of large crystals (Chapter 8 ). Pegmatite
deposits are closely associated with the vein
deposits described above. Granitic pegmatites
–containing quartz, feldspars, amphiboles
and micas as major minerals –occur within
continental plates and at convergent plate
boundaries. Minor and accessory minerals in
pegmatites include beryl, apatite, lepidolite,
spodumene, cassiterite, wulfenite, molybdenite, scheelite, tourmaline, topaz, uraninite,
lithiophillite, columbite, tantalite, gold and
silver. Pegmatites are important sources of
tin, molybdenum, gold and silver and the
primary source for beryllium, lithium, tantalum, niobium and rare Earth element ores.
Figure 19.10illustrates a beryl - bearing granite
pegmatite from the Black Hills of South
Dakota (USA). Let us now briefl y consider
metamorphic processes that occur in regions
surrounding igneous intrusions.
19.1.2 Metamorphic o re - f orming
e nvironments
Metamorphic processes concentrate metallic
elements into ore deposits through solid
state changes as well as hydrothermal fl uid
reactions. Hydrothermal fl uids are critically
important in driving metamorphic reactions
and in concentrating ore metals.
When we think of hydrothermal processes,
Yellowstone or Iceland may come to mind
where hot magma reacts with subsurface
fl uids to create geysers or hot springs. In
fact, hydrothermal deposits are formed by
a number of different means that may originate as meteoric (surface) waters, seawater,
groundwater, formation pore fl uids or deep
magmatic fl uids.
Greenstone b elts
Greenstone belts (Chapter 18 ) are hydrothermally altered assemblages that contain thick
sequences of volcanic suites and interbedded
sedimentary layers. They are called greenstones because of green - colored metamorphic
minerals such as chlorite, epidote and serpentine. Greenstone belts are particularly abundant in Precambrian cratonic belts where they
Figure 19.10 Granite pegmatite from the
Black Hills of South Dakota containing large
crystals of beryl, quartz and feldspar. Gold
deposits are associated with the Black Hills
pegmatite. (Photo by Kevin Hefferan.) (For
color version, see Plate 19.10, between
pp. 408 and 409.)
Figure 19.11 Cobalt mine in the greenstone
belt in Bou Azzer, Morocco. (Photo by Kevin
Hefferan.)
MINERAL RESOURCES AND HAZARDS 551
altered komatiite, basalt and peridotite rocks
(Chapter 10 ) that form at very high temperatures ( > 1400 ° C) near the base of the greenstone assemblage.
Greenstone belts
contact metamorphosed rocks
enriched in calc - silicate minerals
high temperature alteration of
country rocks, usually carbonate rocks, by
the intrusion of silicate magmas. Hot magma
intruding carbonate rock produces ion
exchange via hydrothermal solutions. Minerals such as calcite and dolomite release CO 2
and obtain SiO 2 from the magma; as a result,
a distinctive suite of calc - silicate minerals
form that include calcium pyroxenoid (e.g.,
wollastonite), calcium amphibole
Skarns
skarns that develop in any sedimentary
country rock
Exoskarns
occur in
igneous country rock
endoskarns
form in
geothermal systems, hot springs, hydrothermal vents on the sea fl oor and at convergent
and divergent plate boundaries. In these environments, skarns are commonly associated
with porphyry, pegmatite, vein and VMS
deposits
Modern skarns
formed as a result of chemical
precipitation in shallow marine environments
1.8 – 2.5 billion years ago. These deposits are
well developed in the Lake Superior region of
North America, where they have represented
over 80% of US production since 1900, and
are referred to as Superior - type deposits.
Similar massive deposits also occur in the
Hamersley Basin of Australia, the Minas
Gerais deposits of Brazil and the Kursk region
of Russia
Banded i ron d eposits
consist of alternating iron - rich and
silica - rich layers. The iron - rich layers contain
both ferrous and ferric iron. Ferrous iron minerals include magnetite and siderite, whereas
ferric minerals include hematite and goethite
Superior - type banded iron formations (BIF)
contain iron ore concentrations that occur in metasedimentary
deposits, most of which are Archean contain hematite and magnetite interbedded with volcanic
rocks, graywackes, turbidites and pelagic sedimentary rocks.
form in
deep abyssal basins heated by submarine volcanic activity concentrated iron - rich layers ∼ 30 – 100 m
thick and extending a few square kilometers
in area
Algoma - type d eposits
Tin
Tungsten
Bismuth
Copper
Granitic
plutons in
continental
crust
Copper
Zinc
Gold
Chromium
Backarc
Copper
Gold
Silver
Tin
Lead
Mercury
Molybdenum
Magmatic
arc
Lead
Zinc
Copper
Chromium
Forearc basin
Copper
Zinc
Manganese
Cobalt
Nickel
Oceanic
ridge
similar to Algoma - type deposits in that hydrothermal fl uids leach and concentrate metallic
ore. contain lead – zinc – iron
sulfi des precipitated by submarine hot springs.
Hydrothermal fl uids containing dissolved
metals rise upward and are “ exhaled ”into
clastic sedimentary basins releasing metal - rich
brine solutions into the surrounding country
rock
Sedimentary e xhalative d eposits
form from warm
( < 300 ° C) saline solutions that fl ow in the pore
spaces within permeable carbonate or sandstone rocks in deep sedimentary basins. MVT
deposits precipitate lead and zinc in thick
limestone, dolostone or sandstone deposits
(Figure 19.17 ). These deposits most commonly occur in distal foreland basins where
brine fl ow produces secondary, epigenetic
deposits. In addition to lead and zinc minerals
such as galena and sphalerite, the brine formation waters precipitate halite, sylvite,
gypsum, calcium chloride, barite and minor
amounts of gold, silver, copper, mercury and
molybdenum
Mississippi V alley - type d eposits
uranium occurs in placer deposits
Athabasca Basin)
Canada and Australia are the two largest
uranium exporters in the world
erosional surfaces representing time gaps between depositional cycles.
In Precambrian ( > 1 Ga) cratons consisting
of gneisses and granites, 100 – 300 ° C hydrothermal fl uids leach metals from underlying
rocks and deposit them as ores in tabular
vein deposits along unconformity surfaces
Unconformity d eposits
Major unconformity - derived deposits of
uranium were discovered in
Canada ’ s Rabbit
Lake deposit in 1968 and in Australia ’ s East
Alligator River fi eld in 1970
Sedimentary deposits of uranium occur in
tongue - shaped form in fl uvial
sandstones as dissolved uranium is transported in stream channels. The uranium is
derived from granitic rocks and silicic tuffs.
In the presence of oxygen, uranium is soluble
and moves downstream as a dissolved phase.
Under reducing conditions, uranium precipitates within the pores of sandstone. Variations in oxygen concentrations result in cycles
of dissolution and precipitation producing
irregular, tongue - shaped deposits.
Roll - front d eposits
Laterite soils enriched in
aluminum hydroxide minerals are collectively
referred to as is the
primary source of aluminum, is produced by
the intense leaching of granitic rocks containing aluminum - rich feldspar minerals and, in
some cases, gold ore.
. Bauxite,
derived from
the breakdown of igneous rocks such as
gabbro, pyroxenite or peridotite
Laterites
Laterites are extensively mined in countries such as
China,
Guyana, Australia, Jamaica, New Caledonia,
Brazil, India and Surinam.
precious
metals, (2) light metals, and (3) base metals.
Non -
ferrous metals
alloyed with other elements –such as manganese, cobalt, nickel,
chromium, silicon, molybdenum and tungsten
–to make steel
Ferrous metals
occur largely in their native
state and include platinum, palladium,
rhodium, ruthenium, iridium and osmium.
PGE have similar chemical characteristics,
serving primarily as catalysts in chemical
reactions. Platinum and palladium are the
“ most abundant ”of the rare PGE, occurring
in concentrations of ∼ 5 ppb in Earth ’ s crust.
PGE are obtained primarily from layered gabbroic intrusion
widely used
as the catalysts in automotive catalytic converters, in oil refi ning and in converting
hydrogen and oxygen to electricity in fuel
cells. I
Platinum group
elements (PGE)
PGE are obtained primarily from layered gabbroic intrusions (Chapter 10 ) such as the
Bushveld Complex in South Africa and the
Stillwater and Duluth Complexes in the USA
where PGE occur with chromite and nickel
deposits.
gold bondin gwith silver equals?
electrum
gold bonding with tellurium to form telluride minerals such as
calaverite
silver base metals in sulfi de mineral
argentite, tennantite and tetrahedrite
originate via magmatic processes and concentrate through hydrothermal
reactions in a number of igneous environ r found in placer deposits
typically originate via granitic intrusions,
Precambrian greenstone belts, deep turbidite
sedimentary basins (Chapter 11 ) and as
fi nely disseminated grains within porphyry
copper deposits and VMS deposits. P
Gold and silver
largest gold deposits on Earth
occur in Archean age ( > 2.5 Ga) placer
deposits that formed by weathering granite
source rocks and depositing high density gold
and uranium in a clastic sedimentary basin.
discovered in
1886 and mining continues to this day.
Notable gold rushes in the 19th century,
which included the California and Klondike
gold rushes, also involved placer deposits in
which high specifi c gravity gold fl akes and
nuggets weathered from vein deposits, settled
to the base of streams and were later extracted
by panning techniques
Witwatersrand deposits of South Africa
produce signifi cant tonnage of both
gold and silver
Utah ’ s Bingham copper
mine and the Grasberg copper mine in Indonesia
consist of low density elements
such as magnesium (1.7 g/cm 3
), beryllium
(1.85 g/cm 3
), aluminum (2.7 g/cm 3
) and titanium (4.5 g/cm 3
Light metals
are alloyed with scandium and cored
with light - weight materials such as graphite.
Aluminum baseball
constitutes ∼8% of Earth ’ s
crust by weight, it is a diffi cult metal to obtain
and process. is obtained primarily
from laterite soils that have experienced
extreme leaching in tropical environments.
Laterite soils derived from the weathering of
granitic or clay - rich rocks commonly contain
the bauxite group minerals diaspore, gibbsite
and boehmite. Although bauxite is the only
commercial source of aluminum, this light
metal could be processed from clay or feldspar group minerals at a signifi cantly higher
cost. Whether derived from bauxite, clay or
feldspars, aluminum production requires an
enormous amount of energy.
Aluminum
very expensive, relatively
rare element that occurs in the minerals beryl
and beryllonite. Ore deposits of these minerals occur in silicic pegmatite intrusions and
in related hydrothermal veins
alloyed with copper to increase hardness and
is widely used in computer, telecommunications, aerospace, military and automotive
electronics industries due to its high conductivity, light weight, stability at high temperature and resistance to corrosionis a
known carcinogen and inhalation of this dust is particularly lethal,
Beryllium
about 1% by weight
of Earth ’ s crust and occurs in ore minerals
such as ilmenite, rutile and anatase. occurs in layered gabbroic intrusions
and in coastal placer deposits derived from
the weathering of gabbroic intrusions
light - weight metal with a very
high melting temperature (1678 ° C) and is
widely used in aircraft engines and high speed
turbines. reports that titanium
represent 30% of modern aircraft
weight. Ocean research submersibles such as
the Alvin also consist largely of titanium.
used for
joint replacements and prostheses in the
medical industry.
Titanium
non - ferrous metals that
oxidize easily include copper,
zinc, lead, tin, lithium, uranium, mercury,
arsenic, cadmium, antimony, germanium,
rhenium, tantalum, zirconium, hafnium, inidium, selenium, bismuth, tellurium and
thallium.
Base metals
ccurs in the native state as well as
in sulfi de, oxide, hydroxide and carbonate
minerals.
copper
Zinc oxide minerals
zincite and franklinite were exclusively mined
terling Mine in Franklin, New Jersey,
which ceased operations in the 1980s.
occurs primarily in the sulfi de mineral
galena. Minor minerals include anglesite,
cerussite and crocoite. As noted previously,
lead occurs with zinc in MVT and sedex environments. used since ancient
times in lead crystal glassware, lead glass and
as a sweetener for wine. Physical and mental
debilitation due to ingestion of lead has been
cited as one of the possible causes for the fall
of the Roman Empire.
lead
derived primarily from the
mineral cassiterite and is associated with
silicic igneous intrusions in sedimentary rock.
closely associated with tungsten and
molybdenum ore deposits in granite plutons
and associated hydrothermal vein networks in
continental crust overlying subduction zones.
Tin also occurs in VMS, MVT and placer
deposits.
Tin
obtained from oxide and
phosphate minerals such as uraninite and carnotite in unconformity and placer deposits
derived by weathering granite source rocks.
primary fuel for nuclear reactors and is a major energy source. While the
production of nuclear energy does not emit
the contaminants or greenhouse gases associated with fossil fuels, the mining and disposal
of uranium material poses major environmental problems
Uranium
associated
with a high lung cancer incidence due to inhalation of radioactive radon gas, produced as
a breakdown product of uranium
Uranium mining
another uranium daughter product, is a major
contaminant of groundwater. chemically similar to calcium, it is readily
absorbed into bones causing cancer.
Radium
had been proposed
as a permanent nuclear waste repository but
its future use as of this writing is uncertain
Yucca Mountain, Nevada
include scandium,
yttrium and the 15 lanthanide elements
found in minerals such as monazite, which occurs in granite
pegmatites, hydrothermal veins and placer
depositsused
as catalysts in oil refi ning, in chemical synthesis, as catalytic converters in automobiles, as
glass additives, in glass polishing, in fi ber
optic lasers, phosphors for fl uorescent lighting, in color televisions, cell phones, electronic
thermometers and X - ray screens, and as pigments, superconductors, dopants and more
Rare Earth metals
exhibits the phenomenon of
phosphorescence and is utilized in electrical
equipment such as fl uorescent lights and
cathode ray tubes
phosphor
is an impurity
that alters the optical and electrical properties
of semiconductors.
dopant
Fire - retardant materials, batteries, ceramics and glass.
While antimony use and production is declining,
China, Bolivia, Mexico, Russia, South Africa,
Tajikistan and Guatemala continue to mine antimony
in association with Pb, Zn, Ag, Sn and Wo
Antimony: in stibnite,
tetrahedrite and
jamesonite
Hydrothermal veins with
Cu, Ni, Ag and Au and
in Cu porphyry
deposits
Arsenic: in realgar,
orpiment, enargite,
arsenopyrite and
tennantite
Byproduct of Wo, Mo
and Pb mining in
porphyry deposits
Bismuth: in
bismuthinit
Hydrothermal vein
deposits, MVT deposits
and Kuroko - type VMS
deposits
Antimony: in stibnite,
tetrahedrite and
jamesonite
Toxic aspect used in copper chromate arsenic (CCA)
wood preservatives, herbicides, insecticides and
ammunition. Arsenic use continues to decline due to
adverse health effects that include breathing and
heart rhythm problems and increased risk of bladder,
lung and skin cancer. Producers include China, Chile,
Arsenic: in realgar,
orpiment, enargite,
arsenopyrite and
tennantite
Over - the - counter stomach remedies (Pepto - Bismol),
foundry equipment and pigments. As a non - toxic
replacement for lead, Bi is increasingly being used in
plumbing, fi shing weights, ammunition, lubricating
grease and soldering alloys. Because of its low
melting temperature, Bi is used as an impermeable
low temperature coating on fi re sprinklers. Bi is
mined in China, Peru, Mexico, Canada, Kazakhstan
and Bolivia
Bismuth: in
bismuthinite
NiCd rechargeable batteries for alarm systems, cordless
power tools, medical equipment, electric cars and
semiconductor industry, and steel and PVC pipes for
corrosion resistance and durability. Previously used
as a yellow, orange, red and maroon pigment.
Unfortunately Cd interferes with Ca, Cu and Fe
metabolism resulting in softening of the bones and
vitamin D defi ciency. Because of adverse health
effects, Cd use is declining. Producers include China,
Canada, South Korea, Kazakhstan, Mexico, the
United States, Russia, Germany, India, Australia and
Peru
Cadmium: in
greenockite;
primarily derived
from sphalerite
Byproduct of Zn mining
in VMS and MVT - type
deposits
Cadmium: in
greenockite;
primarily derived
from sphalerite
Fiberoptic cables, where it has replaced Cu in wireless
communication, solar panels, semiconductors,
microscope lenses and infrared devices for night -
vision applications in luxury cars, military security
and surveillance equipment. Gm is also used as a
catalyst in the production of polyethylene
terephthalate (PET) plastic containers and has
potential for killing harmful bacteria. The USA is the
leading producer of Gm
Germanium: rarely
forms its own
mineral but occurs
with Zn and Cu
Byproduct from MVT
deposits and in Cu ore
deposits
Germanium: rarely
forms its own
mineral but occurs
with Zn and Cu
Used in the construction of nuclear rods because Hf
does not transmit neutrons. Major producers of
zirconium and hafnium include Australia and South
Africa
Hafnium: in ilmenite
and rutile
Placer deposits
Hafnium: in ilmenite
and rutile
Indium – tin oxide (ITO) is used in the production of fl at
panel displays and other LCD products. ITO is also
used in windshield glass, semiconductors,
breathalyzers and dental crowns. Major producers of
indium include China, Canada, Belgium and Russia
Indium is in sphalerite,
cassiterite and
wolframite
VMS, MVT and
hydrothermal veins
with Sn, Wo and Zn
Indium is in sphalerite,
cassiterite and
wolframite
Used in glass, ceramics, greases and batteries. Because
of the adverse health issues associated with Cd and
Pb, Li batteries are increasingly being used in power
tools, calculators, cameras, computers, electronic
games, cellphones, watches and other electronic
devices. The primary producers include Chile,
Australia, Russia, China, Argentina and Canada
Lithium: in
spodumene,
lepidolite and
lithiophilite
Granite pegmatites and
alkali brines from playa
basins
Lithium: in
spodumene,
lepidolite and
lithiophilite
Only metal that is liquid at room temperature for
which it is commonly referred to as quicksilver.
Previously used for automotive switches, cosmetics,
pigments, gold processing and hat making. Hg is
highly soluble and readily enters the bloodstream
where it attacks the nervous system causing psychotic
behavior ( “ mad as a hatter ” ), irritability, tremors
and can lead to death. Hg continues to be used in
thermometers, batteries, electrical fi xtures and dental
amalgam fi llings and is used as a catalyst in paper
production. Hg use in these and other capacities will
continue to decline because of its adverse health
effects. Hg is obtained from mines in China or
Kyrgyzstan or obtained as a secondary ore in copper,
zinc, lead and gold mines throughout the world
Mercury: in cinnabar
Low temperature
( < 200 ° C) hydrothermal
vein deposits
Mercury: in cinnabar
Used with Pt as a catalyst in oil refi ning and the
generation of high octane, lead - free gasoline. Re is a
superalloy used in high temperature turbine engine
components, crucibles, electrical contacts,
electromagnets, electron tubes and targets, heating
elements, ionization gauges, mass spectrographs,
semiconductors, thermocouples, vacuum tubes and
other uses. Producers of Re include Chile, the United
States, Kazakhstan, Peru, Canada, Russia and
Armenia
Rhenium substitutes
for molybdenum: in
molybdenite
Cu porphyry deposits
Rhenium substitutes
for molybdenum: in
molybdenit
Decolorized green tints are caused by iron impurities in
glass; reduces solar heat transmission in architectural
plate glass. Together with Cd, Se is used to generate
ruby red colors in traffi c lights, plastics, ceramics and
glass. Selenium ’ s photoelectrical properties were used
as photoreceptors in replacement drums for older
plain paper photocopiers. In the digital age, Se
enables the conversion of X - ray data to digital form.
Se serves as a catalyst in oxidation reactions, and is
used in blasting caps, rubber compounds, brass alloys
and in dandruff shampoos. Se is also used in
fertilizers and as a dietary supplement for livestock.
Se has both positive and negative health aspects:
defi ciencies increase the incidence of stroke while
excess selenium is related to deformities. Major
producers of Se include Japan, Canada and Belgium
Selenium: in selenite
gypsum; more
commonly occurs
with sulfi de minerals
such as FeS and CuS
minerals
Byproduct of Cu ore
deposits
Selenium: in selenite
gypsum; more
commonly occurs
with sulfi de minerals
such as FeS and CuS
minerals
Used in electrical capacitors, automotive electronics,
pagers, personal computers and cell phones. Major
producers of Ta include Australia, Brazil,
Mozambique, Canada, Ethiopia, Congo (Kinshasa)
and Rwanda
Tantalum: in microlite,
pyrochlore and
tantalite
Pegmatites, hydrothermal
veins and placer
deposits
Tantalum: in microlite,
pyrochlore and
tantalite
Used as a semiconductor and as a metal alloy for
ductility and strength. Te is among the rarest
elements in Earth ’ s crust
Tellurium: in calaverite
Pegmatites, veins.
Tellurium: in calaverite
Previously used in rat and ant poison until its toxicity
to humans became apparent. Tl interferes with the
metabolism of K and can cause death. Tl - 201, a
radioactive isotope, is used in the medical industry
for cardiovascular imaging. Tl is also used an
activator in gamma radiation detection equipment,
infrared detectors and in high temperature
superconductors used for wireless communication.
Major producers include Canada, European countries
and the USA
Thallium: in
association with
sphalerite
VMS and MVT deposits
Thallium: in
association with
sphalerite
Used as a fuel in nuclear reactors due to the ease with
which it transmits neutrons; also used in ceramics
and as an abrasive, metal alloy and refractory
material due to its very high melting temperature
(2550 ° C). Major producers include Australia and
South Africa
Zirconium: in rutile
and ilmenite
Placer deposits
Zirconium: in rutile
and ilmenite
Polishing compounds, radiation shield, glass,
ammonia synthesis
Cerium
Permanent magnets
Dysprosium
Fiber optic amplifi er, glass additive
Erbium
Phosphors in cathode ray tubes
Europium
Phosphor and laser crystals
Gadolinium
Dopant in laser crystals
Holmiun
Catalyst in petroleum refi ning, glass additive,
rechargeable batteries
Lanthanum
Phosphor
Lutetium
Permanent magnets, glass additive, dopant in
laser crystals
Neodynium
Yellow pigment in ceramics
Praseodymium
Fluorescent lighting starter
Promethium
Permanent magnets
Samarium
Metal halide lamps
Scandium
Phosphors
Terbium
Isotope used in medicine
Thulium
X - ray source, glass and laser additives
Ytterbium
Phosphor, synthetic gems, superalloy
Yttrium
consist of primary
nutrients such as nitrogen, phosphorous and
potassium, and secondary nutrients such as
calcium, magnesium and sulfur
Fertilizers
Approximately 95% of
world phosphate production is used
as fertilizer and ∼5% is used in products such as
detergents, fi re retardants and toothpaste
Light - weight and high strength metal.
Major producers include Australia, Papua
New Guinea, Jamaica, Brazil and India
Bauxite in laterite deposits derived
from weathering silicic igneous
rocks
Aluminum: diaspore,
boehmite, gibbsite
Granite pegmatites, hydrothermal
veins around silicic igneous
rocks
Light - weight metal stable with high
temperature strength. Major producers
include the USA, China and Mozambique
Beryllium: beryl
Organic or inorganic sources Alloyed for hardness. Producers are
widespread globally
Carbon: graphite
Layered gabbroic intrusions,
ophiolites, VMS, laterites, placer
deposits
Corrosion resistance; important alloy in
“ stainless steel ” . Major producers include
South Africa, Kazakhstan and India
Chromium: chromite
Layered gabbroic intrusions,
hydrothermal veins, evaporite
brines in desert basins
Corrosion and abrasion resistance; used in
industrial and gas turbine engines. Major
producers include Congo (Kinshasa),
Zambia, Australia, Russia, Canada,
Cuba, Morocco, New Caledonia
and Brazil
Cobalt: cobaltite
Marine carbonate rocks and
layered igneous intrusions.
Hardens Al and corrosion resistance.
Magnesium producers are widespread
globally
Magnesium: magnesite,
olivine
Supergene weathering of Mn rich
rocks in laterites; Mn nodules in
VMS; marine limestones and
shales
Corrosion resistance in Al; alloyed with Cu
for strength; replaced lead in fuel. Major
producers include South Africa, Gabon,
Australia, Brazil and China
Manganese: pyrolusite,
psilomelane, rhodonite,
rhodochrosite
Porphyry type deposits and granite
pegmatites
Hardness; corrosion resistance, high
temperature strength. Producers include
the USA, Chile, China and Peru
Molybdenum:
molybdenite
Layered gabbroic intrusions
ophiolites, komatiites and
laterites derived from ultrabasic
rocks
High temperature strength; corrosion
resistance; used in jet engines and
turbines. Major producers include Russia,
Canada, Australia, Indonesia, New
Caledonia, Columbia and Brazil
Nickel: nickelline,
pentlandite, millerite
Clastic sedimentary rocks,
pegmatites and hydrothermal
veins
Deoxidant in steel; increases strength and
corrosion resistance. Silicon producers are
widespread globally
Silicon: quartz
Placer sand deposits (beach dunes)
or from layered gabbroic
igneous intrusions
Light weight and strong; strategic mineral
with limited reserves; six times stronger
than steel; aircraft commonly contain
one - third Ti. Producers include South
Africa, Australia, China and India
Titanium: ilmenite, rutile
Pegmatites and hydrothermal veins
derived from granitic intrusions.
Also skarns, hot springs
High temperature strength; high speed
drills, armor plating, light fi laments.
Major producers are China, Russia,
Kazakhstan, Austria, Portugal and
Canada
Tungsten: scheelite,
wolframit
Pegmatites, veins, layered igneous
intrusions, phosphate
sedimentary rock.
High strength, ductility, toughness; used in
high rises, oil platforms. Major producers
are South Africa, China and Russia
Vanadium: vanadinite,
uraninite
MS or MVT Corrosion resistance. Major producers
include China, Peru, Australia and
Ireland
Zinc: sphalerite, zincite
forms by bacterial reduction of gypsum and other sulfate
minerals and by sublimation from volcanic
gases around vents.
sulfur
consists of
rocks such as limestone, marble, sandstone,
granite, gneiss and slate. Dimension stone has
been used since at least the construction of
the pyramids over 4000 years ago and, until
recently, dimension stone remained the
Dimension stone
used
marble quarried locally in Carrara, Italy.
Vermont slate was the rock of choice for sidewalks, blackboards and roof tiles in the
eastern United States; slate from Wales provided an equal service in Wales and England.
Homes in Ireland and England were largely
constructed of limestone.
Michelangelo
consists of sand, gravel and
crushed stone. derived from unconsolidated sedimentary layers deposited in beaches, deltas,
deserts and stream systems or by glaciers. In
the absence of available sand and gravel, roduced by mechanically crushing rock. The equipment and energy required
to crush rock makes this a more expensive
operation. Due to their low hardness and
abundance, limestone and dolostone are rocks
of choice for crushed
quality is lowered by the
presence of pyrite, which oxidizes to produce
rust, and shale, which weathers easily.
Concrete, developed by the Romans
Aggregate
developed by the Romans 2000
years ago, is the dominant construction material used in world today
Concrete
is made by
heating limestone and clay in a kiln to produce
clinker. Clinker is then ground to a powder
and mixed with gypsum most common hydraulic cement,
meaning that it hardens with water. In many
construction projects cement has replaced
dimension stone because of its ease of transport, workability and the ability to create
forms to fi t site - specifi c construction projects.
Cement quality is affected by the presence of
chert (promotes cracks in concrete), magnesium content (MgO must be <5%) and pyrite
concentration (produces SO 2 gas).
Portland cement
an evaporite mineral that commonly forms in sabkhas or intertidal fl ats of
marine systems. In addition to its use in
cement used in plaster and
wallboard (sheetrock) for building construction
Gypsum
s produced by heating and dehydrating gypsum at
temperatures of ∼ 150 ° C
Plaster of Pari
used to
increase soil aeration and retain moisture and
chemicals in agricultural soils.
Vermiculite
tilize clays and other minerals such
as feldspars, hematite, bauxite, bentonite,
pyrophyllite, borax, wollastonite, barite, lepidolite and spodumene. Clay forms the basis
of pottery and other ceramic materials.
Feldspars, borax and wollastonite are used
to produce ceramic glazes on pottery that
increase hardness, provide a vitreous luster
and preserve color. Hematite serves as a
pigment. Barite hardens ceramics and serves
to preserve pigments. Bauxite and pyrophyllite provide high temperature strength.
Lithium minerals lepidolite and spodumene
are added to ceramics to prevent volume
change with temperature variations.
Ceramic
promote
eutrophication of water bodies by deteriorating water quality due to excessive nutrient
input.
Phosphates
inert, inexpensive materials that
extend the volume of material at low cost include barite and phyllosilicate minerals such as kaolinite, smectite, mica, talc and
pyrophyllite
Fillers
used as a light - weight fi ller in
cement, concrete and plaster
vermiculite
used as
a fi ller in chocolate
Barite
e is used as a
fi ller in ice creams and shakes.
kaolinite
is a siliceous
rock composed of microscopic marine organisms called
diatoms
breaks chemical bonds, thereby lowering the melting temperature of materials
fl ux
Common insulating
materials include
asbestos, micas, silica and
vermiculite
commonly contains amphibole (tremolite) asbestos which is a known carcinogen
as well as a known contributor to mesothelomia and asbestosis
vermiculite
used
in jet engines, turbines and high speed drills
that generate extremely high temperatures. heat - resistant materials that have very high melting temperatures
and are chemically resistant to breakdown.
Refractory minerals
Refractory minerals
(Fe, Al, Sn, Zr, Cr).
High
quality quartz sand, such as from used in glass making, as foundry
sand for making metal molds, and as an abravise
St Peters
sandstone,
Limonite, goethite, spinel, orpiment cadmium, uranium
pigment
Yellow
Azurite, lazurite, zircon, spinel, cobalt
Blue
Malachite, glauconite, epidote, celadonite, atacamite [Cu 2 Cl(OH) 3], barite, chromium
Green
Hematite, cinnabar, iron, mercury, strontium
Red
Realgar
Orange
Azurite, chrysocolla, turquoise
Turquoise
Malachite, dioptase, gaspeite [(Ni,Mg)CO 3], copper
Copper
Vivianite [Fe 3 (PO 4 ) 2 8(H 2O)], aegerine
Blue gray
Hematite, pyrolusite, cuprite, purpurite (Mn 3 PO 4 )
Purple
Lazurite [(Na,Ca) 8 (AlSiO 4 ) 6 (SO 4 ,S,Cl) 2 ]
Lapis lazuli
Montmorillonite, lepidolite, rhodonite, rhodochrosite, titanium, manganese
Pink
Graphite, magnetite, pyrolusite
Gray – black
is non -
crystalline and organic, forming the tusks of
large animals slaughtered for these gem materials.
Ivory
One well - known synthetic
gem is the isometric zirconium oxide crystal
called
cubic zirconia
costume jewelry
imitaion gems
is soft and
fl exible, with a hardness of 4 – 4.5. Platinum
hardness increases substantially when alloyed
with 5 – 10% iridium
Pure platinum
lloyed with silver and copper,
becomes progressively lighter in color with
increasing silver to copper ratio and
becomes
darker in color with increasing copper to
silver content
produced by
alloying 18 karat gold with nickel, copper and
zinc.
White gold
generated by alloying 18
karat gold with silver, nickel and copper.
Green gold
refers to a thin
veneer of gold overlying a base meta
Rolled gold or gold plated
another soft,
fl exible precious metal with a hardness of 2.5
Silver
Silver must be alloyed with 7.5 – 10% copper
to produce a harder
“ sterling silver ”or “ coin
silver ”
refers to the saturation
or purity of a color.
Intensity
is a
function of the frequency of light and is
described as red, orange, yellow, blue, green,
indigo and violet
Hue
refers to the ratio
between the velocity of light through air and
the velocity of light through a mineral substance. Minerals with a high refractive index
(diamond RI = ∼2.4) tend to be more brilliant
than minerals with lower refractive indices
(quartz RI = ∼1.5)
refractive index (RI)
a play of
color characterized by an intermingled rainbow - like assortment of green, yellow, orange
and blue
Gems such as pearls and opals display a
“ mother of pearl ”opalescence
helliodore (yellow)
beryl
(green by day, red by night
Alexandrite
(yellow – green – brown
cat ’ s ey
Demantroid (andradite garnet: green – yellow),
hessonite (grossular garnet: green – yellow), uvarovite
(chromium – green), almandine, pyrope, spessartine
(red)
Garnet
Amazonite
Microcline
Nephrite jade (amphibole)
Tremolite - actinolite
Zircon (diamond like)
Zircon
Tanzanite (violet blue)
Zoisite
enriched in red
wavelengths of light and is relatively depleted
in blue – green wavelengths.
Incandescent light
whereby colors change under different lighting conditions;
photochroism
Ruby, emerald, pyrope, grossular,
uvarovite, tourmaline (GEMS)
Chromium
Dioptase, malachite, azurite
Copper
Sapphire, aquamarine, olivine,
almandine garnet, amethyst
quartz
Iron
Morganite, pink tourmaline,
spessartite garnet
Manganese
Green beryl, blue zoisite, garnet
Vanadium
Blue sapphire
Titanium
e resistance to breakage
Toughness ,
features a
smooth, rounded top and a fl at base, resembling the form of a contact lens
cabochon cut
which is highly prized in diamonds, consists
of fl at, polished, planar surfaces (facets) bounded by sharp angles that result in a sparkling, radiating, adamantine luster.
A faceted cut
The upper
fl at surface is called the
top, bezel or crown
with a fl at tab in the center of the crown
base of the faceted cut is referred to as
pavilion or back
constitutes
those faces between the crown and the base.
girdle
vary in size from microscopic grains to over 3000 karats in weight. 75% e of lower quality industrial grade and the remaining 25% are gem -
quality stones
Diamonds
Gem - quality diamonds are rated and sold according to the four Cs:
carat (karat),
color, clarity and cut.
Refers to the weight of the diamond. One karat is equivalent to 200 mg. s defi ned
of consisting of “ 100 points ”so that a 300 mg diamond is 1.5 karats or 150 points
Karat
is measured from a D (perfectly colorless) to Z (markedly colored) scale where the following ranges exist:
Color
colorless range; these are area and extremely expensive
D – F:
nearly colorless, wherein color is only detected under magnifi cation
G – J:
faintly yellow, wherein slight yellow hues can be noted by the unaided eye.
K – M:
very light yellow, where a light yellow color is obvious.
N – R:
light yellow, where a yellow tinge is distinctly visible.
S – Z:
football - shaped cut with a length : width ratio of ∼ 2 : 1
marquise cu
cut is a rectangular
form with beveled corner edges
emerald
cuts resemble the forms for which they
are named
pear, oval and heart
buying a diamond
affordable karat size (0.5 – 1 karat) and select a nearly colorless G – J color
range and slightly fl awed S 1 clarity rang
controls
∼75% of the global diamond market.
cartel
uranium, radium, radon, polonium and
thorium arsenic, mercury, cadmium and chromium
carcinogen
Aluminum, arsenic, beryllium,
cadmium, copper, indium, lead,
lithium, manganese, mercury,
molybdenum, selenium, tellurium,
thallium, zinc
Teratogenic
Radium, radon, thorium, uranium
Radioactive
involves the excavation of
holes several kilometers wide and over 1 km
deep.
Open pit mining
bones and
teeth composed of hydroxyapatite
[Ca 5 (PO 4 ) 3 (OH)], cryptocrystalline fl uorapatite [Ca 5 (PO 4 ) 3 (F)] and amorphous collophane
are minor components of many sedimentary
rocks. Much rarer are phosphate - rich rocks
called phosphorites that contain more than
50% phosphate minerals and/or 20% phosphate by weight.
or occurrence of phosphorites is in
the form of laminae and beds of cryptocrystalline fl uorapatite and amorphous collophane interlayered with carbonates, siliceous
sediments and detrital mudrocks strata appear nearly
black in outcrop;
Phosphatic materials,
ccumulate in areas where the infl ux
of detrital sediment is minimal, thus ensuring
that phosphate content is high.
Modern examples of such phosphorites
occur mostly as crusts near the sediment –
water interface, in fairly shallow (30 – 500 m)
tropical to subtropical waters (latitude < 40 ° ),
beneath areas of upwelling
is medium to
dark brown and isotropic in thin section
collophane
indicated by the average amounts of carbonaceous material in sandstones (0.05%), limestones (0.3%) and mudrocks (2.0%), preservation of organic
matter occur when large quantities of organic
matter are produced in surface environments
that are depleted in oxygen so that bacterial
decomposition is inhibited
CARBON - RICH SEDIMENTARY
ROCKS AND MATERIALS
organic soils such as
histosols
Anoxic swamps
typically develop
in paralic shoreline environments, especially in parts of deltaic systems
bypassed by distributary channels
woody plants did not
inhabit terrestrial environments until the
middle Devonian, coal deposits do not occur
in rocks older than Devonian and do not
become abundant until the
Carboniferous
Coals are commonly associated with
(1) soils,
especially vertisols and histosols, (2) mudrocks
such as tonsteins and bentonites and (3) a variety of marine – terrestrial transitional and lacustrine facies.
soft, somewhat porous, and possesses a
brownish color and rather dull luster (Figure
14.30 ). Carbon content in the organic fraction is relatively low (50 – 70%) and volatile
content (including moisture) is high (45 –
55%) water
(H 2O), carbon dioxide (CO 2), hydrogen (H 2 )
and methane (CH 4)
Lignite
burial and heating of
lignite, which increases carbon content, drives
off volatile components and transforms some vitrintie less porous
and slightly more refl ective than lignite
Sub - bituminous
coal
half
of the available coal reserves worldwide and
are used primarily as fuel in electric power -
generating stations when burned
they have an especially large potential to
produce signifi cant amounts of airborne pollutants contributors to acid rain and global
warming
Sub - bituminous
coallow rank coals soft coals.
organic molecules that contain
hydrogen and carbon as essential constituents.
hydrocarbons
consists of very
light molecules, dominated by chain - structured alkanes such as methane (CH 4), ethane
(C 2 H 6) and propane (C 3 H 8) with the general
formula C n H 2n+2
Dry gas
consists of somewhat heavier molecules, including alkanes
such as butane (C 4 H 10) and ring - structured
cycloalkanes such as cyclobutane (C 4 H 6) and
cyclohexane (C 6 H 12) with the general formula
C n H n.
Wet gas
temperatures less than
50 ° C, bacteria convert some of the sapropels
to methane while increases in temperature
produce thermocatalytic conversion of sapropels to important
constituents of oil shales
kerogens, which are composed of very
heavy, insoluble organic molecules.
begins to
convert kerogens into crude oil and natural @100C
catagenesis
Conversion of petroleum
to wet gas reaches a maximum near 125 ° C
and dry gas conversion peaks near
150 ° C
organic material is cooked to
temperatures of 60 – 120 ° C, the ∼ 2.0 – 4.5 km, At lower
and higher temperatures, only kerogens and
natural gas are produced and, at still higher
temperatures ( > 200 ° C), very few hydrocarbons remain.
oil
window
The
rocks in which crude oil and natural gas eventually accumulate are called
reservoir rocks
impermeable rocks, typically mudrocks or evaporites, overly the oil trap or reservoir and keep
oil from rising toward the surface, they ar
cap rocks
Petroleum traps that involve geological
structures produced by deformation such as
folds and faults are c
structural traps ;
e produced by depositional patterns that
trap petroleum in reservoir rocks are
stratigraphic traps
results from increasing temperature
and/or pressure conditions over time.
Prograde metamorphism
occur due to
processes such as recrystallization, neocrystallization and other processes induced by
increasing pressure and/or temperature
Mineral replacement and transformation
decreasing temperature and/or pressure so that
lower temperature/pressure mineral assemblages develop that overprint earlier peak temperature/pressure mineral assemblages. Volatile
components serve as catalysts
Retrograde metamorphism
use of
mineral assemblages or deformation characteristics of specifi c minerals to infer peak temperature and/or pressure conditions of
metamorphism
Geothermobarometry
onset of metamorphism begins at
∼ 150 –
200 ° C
The higher
temperature/pressure range of diagenesis
marks the transition to low grade metamorphism (Figure 15.1 a). Progressively higher
temperatures and/or pressures result in
higher grades of metamorphism
∼ 600 – 800 ° C
fl uids derived from magma,
principally at ocean spreading ridges,
magmatic arcs and over hotspots.
“ Juvenile ”
Fluids and vapors containing serve as catalysts in
metamorphic reactions.
H 2O, CO 2 ,
CH 4, K, Na, B, S and Cl
bulk composition of rocks changes as a result
of chemical reactions with hot fl uids of variable origin
occurs via deuteric reactions and metasomatic reactions.
Hydrothermal a lteration
known as formation
pore fl uids, stored in spaces between
grains or crystals
Connate fl uids,
involve reactions in which
igneous rocks are “ stewing in their own
juices ” . Hot, vapor - rich fl uids are commonly
associated with igneous intrusions that
provide the heat, fl uid and corrosive compounds to chemically alter minerals. Minerals
produced by deuteric reactions include albite,
calcite, epidote, sericite, chlorite, serpentine
and talc
Deuteric reactions
involves changes in solid
rock composition resulting from hydrothermal fl uids exchanging constituents with an outside source
involve
leaching, whereby elements are removed
from the rock, as well as precipitation,
whereby elements are introduced by hydrothermal fl uids into the rock from an outside
source
important
process in submarine volcanic settings such
as the oceanic ridge system where basaltic
magma interacts with seawater
Metasomatism
Magma
containing calcic plagioclase (e.g., laboradorite) reacts with sodium - rich seawater;
ionic exchanges occur that convert the calcic
plagioclase into sodic plagioclase (e.g.,
albite) in a process
spilitization
aluminum - rich rocks
such as shale, mudstone and altered volcanic
tuff (bentonite)
Pelite
commonly include minerals enriched in SiO 2 ,
Al 2 O 3 and K 2O. With increasing temperature
and pressure, clay minerals such as kaolinite,
smectite and illite become unstable and are
transformed into the aluminosilicate minerals
pelitic metamorphic rocks
e US Occupational Safety and Health Administration (OSHA) defi nes minerals as fi liform minerals with lengths greater than 5 μm, diameters less than 5 μm and length : width ratios > 3 : 1.
These minerals are considered fi brous if their length : width ratio is greater than 10 : 1
Asbestos
oft, curly, fl exible fi bers and constitutes ∼95% of all the asbestos
used in industry.
Chrysotile
hard and brittle.
represent <5% of all asbestos used in industry.
amphibole
lung tissue encapsulates asbestos particles. weakens the heart and destroys
the lungs.
Asbestosis:
lining of the lung and stomach caused by asbestos.
35 – 40 - year
whereby individual atoms or molecules can
migrate in gaseous, liquid or solid phases
from one location in a rock body to a new
location
high viscosity inhibits
migration whereas low viscosity enhances
molecule migration
Diffusion
s small, angular grains that infi ll between
larger grains as in cement mortar produce a mortar texture . high strain rate fault
zones within the upper crust as well as in rare
meteorite impacts.
Cataclasis
dissolution of solid grains under high compressive stress conditions. High, localized
compressive stress regimes result in alterations to the crystal lattice structure so that an
aqueous phase is produced at high stress sites.
Pressure solution
one grain impinges
upon another grain, initiating a soluble phase
in the indented grain
Dissolution occurs
As soluble minerals dissolve, insoluble minerals (iron oxides,
micas, graphite) accumulate as an insoluble
seam called a
stylolite
nucleation
and growth of new minerals as pre - existing Diffusion enhances the
nucleation and growth of new minerals
Neocrystallization
now known to predate the Cretaceous –
Tertiary extinction by 300,000 years
Chicxulub
meteorite
also known as Barringer
Crater –is now thought to have formed
25,000 – 50,000 year ago by ~50 m diameter
of the southwestern USA, is ∼ 1.2 km in diameter and
180 m deep
rim has been
uplifted 30 – 60 m due to debris
Meteor Crater ’ s
long considered a layered intrusive
igneous complex, is now also recognized as a
meteorite impact structure
1.85 Ga Sudbury Complex of
Ontario
non - uniform stress in fault zones and shear
zones
Dynamic m etamorphism
Within the upper
5 km of Earth ’ s surface, the brittle crushing
and grinding of rocks produces
s fault breccia
or a m é lange
partially melted rocks that form by
quenching under high strain rates in shear
zone fractures
Pseudotachylites
heat from the igneous intrusion produces a metamorphic
aureole
occurs when magnesium - rich olivine or pyroxene minerals are altered to
serpentinite by seawater - derived hydrothermal fl uids.
Serpentinization
a result of the
exchange of sodium from seawater for calcium
in plagioclase, which converts the plagioclase
into albite.
Spilitization
ame for sodium - rich
basalts that form along ocean ridges and volcanic arcs. occur in Precambrian greenstone belts and in ophiolite
spilites
Notable modern - day examples of burial
metamorphism
Bay of Bengal and
the Gulf of Mexico and pull - apart basins in
southern California
regional
metamorphism induced by increases in both
pressure and temperature. dominates
convergent margins and associated fold and
thrust belts. combines
a complex set of processes that involve crustal
shortening due to the convergence of two
lithospheric plates
All of the great mountain belts –Himalayas, Alps, Atlas, Urals,
Pyrenees, Carpathian, Cordilleran, Zagros,
Andes, Appalachians –formed as a result
of crustal shortening and igneous activity
and are the sites of intense
dynamothermal
metamorphism
ng normal forces of
equal (uniform) or unequal (non - uniform)
magnitude that intersect a principal plane at
right angles
principal stress axes
parallel to two principal stress axes and
normal (perpendicular) to the third stress
axis.
principal planes
playground analogy
playground analogy
refers to the uniform compressive force directed radially inward by the
surrounding mass of water
Hydrostatic stress
refers to a uniform compressive
force exerted radially inward due to the mass
of surrounding rock. Rock stresses are commonly expressed in kilobars (kbar), megapascals (MPa) or gigapascals (GPa). Most rocks
have a density of ∼ 2.6 g/cm
Lithostatic stress
displacement ,
means that an object has moved from one
point to another point
Translation
development
from an initial to a fi nal state study describes a series of strain events resulting in a fi nal strain state.
e kinematic strain
refers to one or more intermediate strain steps
describing separate strain conditions
Incremental strain
that no rotation of the
incremental strain axes occurred from an
initial to fi nal strain state
Coaxial strain
how
materials respond to stress
Rheology
a linear relationship exists between stress and strain so
that the strain is proportional to the amount
of stress
Hooke ’ s law, elastic behavior
a measure of the angular changes to
linear features. Rigidity (G), also known as shear modulus, is a measure of resistance to change in
shape. For elas
Shear strain
is a measure of resistance to change in
shape
Rigidity (G), also known as shear modulus,
described in terms of length change (translation), shape change (strain or
distortion) and volume change (dilation). Length change, represented by the symbol e, refers to
elongation of a linear feature
Elastic behavior
measure of the resistance to a change in shape incompressibility
e bulk modulus
measure of material “ fattening ”compared
to its “ lengthening ”i change
in object diameter divided by change in object length. ange from 0 to 0.5, which means that all Earth materials increase in diameter and decrease in length in response to compressive stres
Poisson ’ s ratio
e slope of the stress – strain line elasticity is a constant of proportionality that
describes the slope of the line.
Young ’ s modulus of elasticity
marked by the appearance of wollastonite
and the absence of hydrous minerals such as
phlogopite
Calcareous rocks
are hypersthene - bearing granitic gneisses
Charnockites
occurs in
the highest temperature dynamothermal metamorphism region at (1) convergent plate
boundaries, (2) at the base of thick continental crust, and (3) in the uppermost part of the
mantle
corresponds with the
upper parts of the Barrovian sillimanite zone
and –at still higher temperature –the cordierite - garnet zone.
Granulite facies metamorphism
low pressure fi eld of granulite facies metamorphism grades into the
pyroxene and
sanidinite hornfels facies
higher temperature granulite
migmatites of the granulite
facies are produced.
moderate to high pressure (4 – 20 kbar ≈ 13 –
66 km depth), low temperature (150 – 500 ° C) minerals include
magnesio - riebeckite, lawsonite, jadeite pyroxene, aegirine, crossite and kyanite form in subduction zones where
oceanic lithosphere is forced downward to
great depths at geologically rapid rates
blueschist facies
e serves as a
proverbial icicle in Earth ’ s interior
Subduction of oceanic lithosphere
With increasing temperature and pressures exceeding 12 kbar,
blueschist facies converts to the
eclogite facies.
develops at high temperatures (400 – 900 ° C)
and very high pressures (12 – 25 kbar ≈ 40 –
82 km
chemically similar to a silica - undersaturated, anhydrous basalt and generally develop
from basic protoliths. commonly with
reddish brown garnet porphyroblasts conditions include pyrope, majorite, and to a
lesser degree, grossular
Eclogite facies
Eclogite facies rocks occur in three major
environments:
In the lower continental crust and mantle
( > 40 km depth) and later exposed on
Earth ’ s surface in deeply eroded fold and
thrust belts.
2 At convergent margins in ophiolite complexes and subduction zone m é langes.
3 As xenoliths in diamond - bearing kimberlite pipe
youngest
documented eclogites in the world, produced
along the
oblique subduction zone. Oblique subduction involves components of both thrusting and strike - slip
faulting
Papua New Guinea
minerals occur
within the eclogite facies at pressures > 25 kbar ( > 80 km depth) and temperatures > 600 ° C. U
Ultra - high pressure (UHP)
high pressure minera
Majorite
fi rst dynamothermally produced coesite in
Alpine rocks.
distributed along continent – continent collision zones such as in the Alpine –
Himalayan belt, the Ural Mountains, the
Western Gneiss region of Norway and in
pan - African belt rocks
UHP
two low pressure
and high temperature facies series are recognized: (1) the very low P/T contact
facies series, and (2) the somewhat higher
P/T Buchan facies series. T
Low P/T series group:
the high P/T group
includes the Sanbagawa facies series and
Franciscan facies series, represented by
zone C i
High P/T series group
consists of relatively low
pressure ( < 2.5 kbar ≈ 8 km depth) but moderate to high temperature mineral assemblage
recorded by the series of hornfels facies; each
of the individual facies is defi ned based on a
low pressure assemblage of minerals stable
at specifi c temperature ranges
Contact facies series
With increasing temperature the contact
facies series progresses through the sequence
(1) zeolite facies, (2) albite - epidote hornfels
facies, (3) hornblende hornfels facies, (4) the
rarer pyroxene hornfels facies, and (5) at very
high temperatures, sanidinite hornfels facies
record high geothermal gradients ranging from 40 to 80 ° C/km northeastern Scotland
also known
as the Abukuma facies series
individual facies efi ned by low to moderate
P/T mineral assemblages.
efl ects
higher temperatures, but only moderate
increases in pressure.
develop by regional metamorphism and magmatic arc activity at convergent margins.
Buchan f acies s eries
Buchan facies series progresses, with
increasing temperature and pressure,
(1) zeolite, (2) prehnite - pumpellyite, (3) greenschist, (4) amphibolite, to (5) the high temperature, moderate pressure granulite facies
develop in response
to geothermal gradients of ∼ 20 – 40 ° C/km,
refl ecting the progressive increase in both
temperature and pressure during regional
metamorphism
Barrovian facies series
are produced
under geothermal gradients in the range of 10
to 20 ° C/km refl ects the rapid increase of pressure relative to temperature during progressive
regional metamorphism at convergent plate
boundaries slightly higher temperatures. This may result from (1) slower subduction giving the rocks more time to heat up as
pressures increase, or (2) higher geothermal
gradients during subduction.
Sanbagawa facies
The Sanbagawa facies series progression includes (
zeolite, (2) prehnite - pumpellyite, (3) blueschist facies, followed in some
cases by (4) greenschist, and/or (5) amphibolite facies.
develop where
geothermal gradients are < 10 ° C/km. Franciscan facies rocks are characterized by unusually high P/T ratios during progressive
metamorphism. rapid increase in pressure relative to slow increases in tem e high pressure minerals jadeite,
glaucophane and lawsonite are particularly
important indicators of the high pressure, low
temperature conditions. Kyanite, the high
pressure polymorph of aluminum silicate, and
phengite are common in pelitic rocks
Franciscan facies series
The Franciscan facies series progresses from
(1) zeolite, (2) prehnite - pumpellyite, (3) blueschist, possibly to (4) the eclogite facies
a means by
which petrologists predict equilibrium assemblages of minerals in many systems, including
both igneous and metamorphic rocks
phase diagram
. Such equilibrium mineral
reaction and assemblage diagrams are referred
to as
petrogenetic or paragenetic grids
refers to the conditions under which
the rock originated, whereas the term paragenesis refers to the formation sequence of an
equilibrium set of minerals that formed at
different times, e.g., along a metamorphic
temperature – pressure trajectory.
is based on the molecular amounts of
three components, ACF, where A = (Al 2 O 3 +
Fe 2 O 3 ) − (Na 2 O + K 2O), C = (CaO –3.33P 2 O 5 )
and F = FeO + MgO + MnO.
used to depict average
compositional differences between the fi ve
major compositional groups of metamorphic
rocks: (1) aluminum - rich pelitic rocks, (2)
calcium/magnesium - rich, aluminum - poor calcareous rocks, (3) magnesium/iron - rich ultrabasic rocks, (4) iron/magnesium/calcium - rich
basic rocks, and (5) quartz feldspathic rocks
that contain on average similar amounts of all
three components
ACF ternary diagram
is used to discriminate equilibrium mineral
assemblages derived from pelitic and quartzo -
feldspathic protoliths with excess Al 2 O 3 and
SiO he three
apices indicate the following: A ′ = (Al 2 O 3 +
Fe 2 O 3 ) − (K 2 O + CaO + Na 2O), K = K 2O and
F = (FeO + MgO).
A′KF diagram
for metamorphic
rocks where A = Al 2 O 3, F = FeO and
M = MgO useful in discriminating mineral compositions
in ferromagnesian - rich basic and ultrabasic
rocks as well as many pelitic rocks.
AFM diagram
have also been developed for calcareous rocks as illustrated i are CaO, MgO and SiO 2.has powerful applications in the depiction of mineral assemblages in calc - silicate
rocks (containing minerals such as calcite,
dolomite, wollastonite and diopside) and
CMS ternary diagrams
drawn on ternary diagrams
between equilibrium minerals that coexist
under specifi c temperature and pressure conditions.
Tie lines
used as a predictive
model for mineral assemblages in rocks. In
the real world, where the number of components is generally more than three, mineral
assemblages are more complex than the simple
diagrams presented above
Ternary diagrams
extensive hydrothermal metamorphism of basalt, gabbro and
peridotite occurs at ocean ridges resulting in
albite - epidote hornfels, zeolite and prehnite -
pumpellyite facies mineral assemblages
At
deeper levels within the oceanic crust and
upper mantle, gabbro and peridotite are
altered to higher temperature
hornblende
hornfels facies assemblages
occurs on
the ocean or trench side and consists of
Sanbagawa or Franciscan facies series
rocks, characterized lower thermal gradients and high P/T to very high P/T mineral
assemblages Rapid,
steep subduction favors the development
of very high P/T ratios that characterize
the Franciscan facies series, whereas
slower, shallower subduction favors the
development of the moderate to high P/T
ratios that characterize the Sanbagawa
facies series
The outer metamorphic belt
contains hornfels, zeolite and
prehnite - pumpellyite facies metamorphism from early ocean ridge alteration.
However, these rocks are commonly overprinted by more recent greenschist facies
and high pressure assemblages such as
blueschist and eclogite facies rocks due to
burial in the subduction zone. exposed in subduction zone complexes,
accretionary wedges and m é langes
outer metamorphic
belt
occurs on the
continent or arc side and consists of
Buchan or Barrovian facies series rocks,
characterized by moderate to high temperature gradients and by moderate P/T to
low P/T mineral assemblages marked by the occurrence of hornfels,
zeolite, prehnite - pumpellyite, greenschist,
amphibolite and granulite metamorphic
facies produced by arc magmatism and
compressive stresses. Notably absent are
high pressure assemblages of the blueschist and eclogite facies. The inner metamorphic belt occurs along the magmatic
arc complex
inner metamorphic belt
The subduction of relatively cold lithosphere to depths as great as 700 km produ
high P/T Sanbagawa and Franciscan facies
that occur only in association with ocean
plate subduction.
ater be incorporated into
forearc accretionary wedges and m é langes,
discussed below.
ocated on the overriding
plate between the trench and the volcanic arc,
include the accretionary wedge (prism),
forearc basin and forearc basement
Forearc a ccretionary w edges and m é langes
produced within the
forearc accretionary prism chaotic mixture, commonly contains fragments of rocks that
include basalt, gabbro, peridotite, chert, limestone, sandstone, serpentinite, phyllite, zeolite,
prehnite - pumpellyite, greenschist, amphibolite, blueschist and eclogite rock fragments
encased in a scaly mudrock matrix.
Tectonic m é langes
enriched in pore fl uids that are expelled upon
further compression to produce a scaley
matrix
accretionary m é lange matrix
Highly faulted ophiolite complexes commonly occur in accretionary
wedges. Because of their location above
subduction zones form by the offscraping and offslicing of oceanic and/or arc
lithosphere resulting in the emplacement of
oceanic/arc lithosphere fragments onto the
overriding hanging wall plate
supra - subduction zone (SSZ)
ophiolites.
mineral assemblages, the
diagnostic facies of Phanerozoic subduction
zones, are exposed in subduction m é langes
within the accretionary wedge of most young
convergent margins. The subduction m é lange
is characterized by a diverse suite of metamorphic facies including high P/T blueschist and
eclogite assemblages of the Franciscan and/or
Sanbagawa metamorphic facies series (
Blueschist facies
develop
between the uplifted accretionary wedge/
subduction zone complex and the volcanic
arc occur between the
high P/T rocks of the accretionary prism and
the low P/T paired metamorphic belts of the
magmatic a ommonly affected by burial metamorphism due to deposition of volcaniclastic
sediment derived from the adjacent volcanic
arc. Total basin - fi ll thicknesses can exceed
10 km, resulting in zeolite to prehnite - pumpellyite facies assemblages underlain by forearc
basement, which consists of overriding plate
rocks that existed prior to subduction as well
as younger volcanic – magmatic arc material
that formed after subduction began
Forearc b asins and b asements
consists of deep intermediate to silicic plutons
that are overlain by the composite volcanoes
of the volcanic arc uration and aerial
extent of igneous activity leads to long - term,
intense heating of rocks in the overlying plate.
This heating creates higher than normal geothermal gradients ( ≥ 40 ° C/km) generating
contact, Buchan and, to a less degree, Barrovian facies series assemblages
Magmatic a rc c omplexes
Progressive
Buchan facies series metamorphism generates
regionally developed
zeolite, greenschist,
amphibolite and granulite facies
moderate to low P/T Buchan and Barrovian facies
series rocks are well developed throughout
the world, including the
Pacifi c rim, eastern
Indian Ocean, Caribbean and Scotia region.
Ancient examples occur in the Caledonian,
Appalachian, Ural and Alpine – Himalayan
fold and thrust belts
develop in response to tensional stresses
within the arc complex extension in an ocean – ocean convergent
margin, such as in the western Pacifi c Ocean,
results in the generation of actively spreading
marine backarc basins that can eventually
evolve into marginal seas also form in ocean – continent convergent
margins, as for example in the Tyrrhenian
Sea. Zeolite and prehnite - pumpellyite facies
as well as hornfels facies metamorphism occur
at relatively shallow depths. Greenschist facies
temperatures can be attained at greater depths.
Backarc b asins
form as a result of trans -
tensional stress in oblique - slip environments
or along bends in faults Local
extension produces a down - dropped block
which infi lls with sediments with thicknesses
capable of producing burial metamorphism occur in transform,
divergent or convergent plate boundaries as
well as within plate settings. ubjected to sub - greenschist
conditions in the zeolite and prehnite - pumpellyite facies. California ’ s San Andreas Fault.
Pull - apart basins
in the overlying plates of many convergent
margins. Formerly gently dipping to horizontal continental slope and continental shelf
sedimentary rocks –such as shales, limestones, dolostones and sandstones deposited
in passive marine settings –are subjected to
intense subhorizontal compressive stress
Sevier fold
and thrust belt and Rocky Mountain foreland
basin (Figure 18.30 ) developed in the Mesozoic and Early Cenozoic in response to subduction activity. In the fold and thrust belt,
Precambrian, Paleozoic and Mesozoic sedimentary rocks were folded and displaced eastward by thrust faults. Syn -to post - orogenic
magmatism intruded the fold and thrust belt
Ocean – c ontinent c onvergence: f old and t hrust
b elts and f oreland b asins
accommodated by
folds and thrust faults that result in the telescoping or “ piggybacking ”of thrust slice
horizontal shortening
In the
adjoining foreland basin, an initially deep
basin fi lls with marine deposits producing
alternating shale, sandstone, chert and carbonate layers producing what is referred t
fl ysch deposit
With continued thrusting and
infi lling, fi ne - grained marine rocks are succeeded by sandstones and conglomerates in
what are referred to as
molasse
important for the generation of oil and gas
deposits as well as extensive lignite, bituminous and anthracite coal deposits.
Fold and thrust
belts and foreland basins
develops –marking the former site of the
subduction trench –within an accretionary
m é lange containing intensely deformed rocks
which can include ophiolite, forearc fragments, blueschist, ocean plateaus and ultra -
high pressure (UHP) assemblages
suture zone
produces vertical uplift and intense
lithospheric thickening accommodated by
folding and thrust faulting, producing
widespread classic Barrovian facies series
assemblages
Continued horizontal
shortening
The elevated temperatures and
pressures produce This situation is well
displayed in the Himalayan belt, which contains the highest mountain peaks on Ea
greenschist, amphibolite
and granulite facies refl ecting geothermal gradients ranging from ∼20 to 40 ° C/km in the
Barrovian facies series
contain an uplifted Tibetan
Plateau, suture zone and fold and thrust belt
that formed as a result of continent – continent
collision.
Himalayan
Mountains
Eruptions begin as fi ssures, evolving to central vent fl ows
and the generation of large shield volcanoes, fi ery
basaltic lava fountain eruptions, quiet lava fl ows and
cinder cones
Kilauea, Hawaii
Hawaiian
Persistent fi ssure eruption of low viscosity basaltic lava
fl ows. Prolonged quiet eruptions may generate lava
plateaus and fl ood basalts
Laki, Iceland, 1783
12 km 3
of lava
Icelandic
Explosive, steam - blast eruptions with lava fl ows and
pyroclastic debris. Surtseyan eruptions are named after
the volcanic island of Surtsey, which rose above sea level
on November 14, 1963. Within 2 months Surtsey, a
newly created island south of Iceland was 1.3 km long
and 174 m high (Decker and Decker, 2006 ). Surtsey
continued to erupt until 1967
Surtsey, Iceland, 1963
Surtseyan
(phreatomagmatic)
Periodic bursts ( “ burps ” ) of moderately explosive eruptions
( < 5 km high) with great concentrations of pyroclastic
fragments and incandescent basaltic lava fl ows
Stromboli, Italy
Strombolian
Explosive eruptions of basaltic to rhyolitic viscous lava and
large volumes of volcanic ash plumes ( < 25 km high) and
pyroclastic debris
Vulcano, Italy
Explosive eruptions
Vulcanian
Violent eruptions of volcanic debris ejected, scattering ash
over thousands of square kilometers
Mt Vesuvius, Italy
Vesuvian
Tephra eruptions emit immense ash clouds > 11 km in
height into the stratosphere
Krakatoa, 1883
Plinian
Violent tephra eruptions of volumes > 1 km 3
and ash cloud
heights 25 – 55 km
Mt Taupo, New
Zealand, 181 AD
Ultraplini
consist of concentrically layered (zoned) plutons formed in convergent margin settings everal kilometers in diameter,
exhibit a dunite core and pyroxenite shell,
and are surrounded by massive gabbro. Late
granitic zones may also occur around the
perimeter of the intrusive structure. In contrast to tectonically emplaced alpine suite form in situ by intrusion
of magma into the surrounding country rock commonly occur as post - orogenic intrusions in
volcanic arc or accretionary m é lange terrains economically important as sources of metals,
particularly platinum group elements (PGE)
Alaska - type intrusions
remains an active exploration site with
economic deposits of copper, nickel, platinum
and palladium
Duke
Island
refers to magma generation and igneous rock suites generated
within lithospheric plates, rather than at plate
boundaries. Tholeiitic to alkalic basalt and related
gabbros of hotspots and LIP.
* Siliceous anorogenic granite and rhyolite.
* Silica - undersaturated rocks.
* Basic – ultrabasic suites including komatiites and kimberlites.
* Carbonatites.
Intraplate magmatism
ncompassing
volumes > 10 6
km 3
(Mahoney and Coffi n,
1997 ), are the greatest manifestation of intraplate magmatism on Earth basaltic in composition although
silicic examples, known as SLIP (silicic large
igneous provinces), such as Yellowstone, also
occur. most widespread Phanerozoic
intraplate magmatic features consist of
massive tholeiitic fl ood basalts. These massive
volcanic landforms occur as both oceanic
fl ood basalts and continental fl ood basalts
Large igneous provinces (LIP),
are a geochemically distinct suite of rocks distinctly different
from MORB ( OIB are more alkalic and are less
depleted –and may in fact be somewhat
enriched with respect to incompatible elements such as potassium, rubidium, uranium,
thorium and LREE OIB were considered to perhaps represent partial melts from a deeper, undepleted
mantle source. However, ocean island basalts
display large variations in strontium, neodymium and lead and other isotopic ratios,
suggesting the role of multiple sources and
processes Small degrees of melting of a primitive
mantle source.
* Melting of a mantle source enriched in
alkali elements.
* Incorporation of subducted oceanic crust
in the source region.
* Entrainment of subducted sedimentary
rocks in the source region
t magmas were derived from non - primitive
sources of variable mantle composition. For
example, Rb/Sr and Nd/Sm ratios are lower
than primitive mantle ratios while U/Pb, Th/
Pb and U/Th ratios are higher than primitive
mantle sources display isotopic ratios indicative of an enriched mantle source, particularly their elevated incompatible element and
NiO concentrations
Ocean island basalts (OIB)
Hawaiian Islands
constitute the highest mountains on Earth
with a relief of ∼ 10 km high; Mt Everest in
contrast has an elevation of just over 9 km.
Hawaiian hotspot has been active for
over 80 million years, generating a chain of
seamounts and islands extending for a distance of 5600 km dominated by olivine tholeiites; tholeiitic
basalts comprise ∼99% of the exposed Hawaiian volcanic rocks with alkalic basalts contributing only a small fraction
Hawaiian
results
from fractional crystallization of early formed,
magnesium - rich olivine and pyroxene
The dominant tholeiitic iron -
enrichment trend
ocated near the
Solomon Islands in the western Pacifi c Ocean,
is the largest oceanic fl ood basalt plateau on
Earth asalts erupted either in a single
massive fl ood eruption ( ∼ 122 Ma) or in a
series of eruptions spread over 10 million
years with the initial massive outpouring
occurring ∼ 122 Ma. T Ocean Drilling Project (ODP) rock core
analyses, hought to consist largely of a relatively
homogeneous low potassium tholeiite that
erupted as massive sheet fl ows and pillow
basalts, accompanied by minor volcaniclastic
and vitric tuff deposit was derived by 30% melting of a
primitive, enriched, high magnesium (15 –
20 wt % MgO) mantle source.
Ontong – Java basalt
include the Deccan traps
of India, Karroo basalts of Africa, Siberian
fl ood basalts of Russia and the Columbia
River, Snake River plain and Keweenaw fl ood
basalts of the United States
Continental fl ood b asalts
The three largest
fl ood basalt events –the
Permo - Triassic
Siberian traps, the Triassic – Early Jurassic
Central Atlantic Magmatic Province and the
Cretaceous – Tertiary Deccan traps –correspond with the largest extinction events in
Earth ’ s history
silicic - dominated provinces containing rhyolite caldera complexes and ignimbrites
SLIP
formed during the Early Jurassic
break - up of the Pangea supercontinent, which
produced rift basins and fl ood basalts in
North America, South America, Europe and
Africa rocks
consist of tholeiitic to andesitic basalts, with
rare alkaline and silicic rock
CAMP
consist predominantly of tholeiitic basalt
fl ows tens to a few hundreds of meters thick
with minor trachyandesites, nephelinites, picrites, volcanic agglomerates and tuffs
Siberian fl ood basalts
were already recognized as one of the
greatest known outpourings of lava when, in
2002, the western Siberian Basin fl ood basalt
province was discovered which effectively
doubled the aerial extent of the Siberian traps
to approximately 3,900,000 km 2
251 Ma Siberian fl ood
Over 1,000,000 km 3
of fl ood basalt erupted
in southwestern India between 65 and 69 Ma encompass an area of
500,000 km 2
in western India elated dike swarms are interpreted to
result from rifting as the Indian Plate migrated
over a mantle plume dominated by tholeiitic
basalts with minor amounts of alkalic basalts.
Geochemical studies suggest that the Deccan
basalts originated by fractional crystallization
of shallow magma chambers ( ∼ 100 kPa, 1150 – 1170 ° C). The basaltic magma experienced variable degrees of contamination as it
ascended and assimilated granitic crustal
rocks
Deccan t raps
are among the most studied CFB on
Earth. consist
largely of quartz tholeiites and basaltic andesite, with 47 – 56 wt % silica The Grande Ronde Basalt,
which erupted 15.5 – 17 Ma, comprises
approximately 87% of the total volume of the
Columbia River basalt Over 300 individual lava fl ows erupted
from northwest trending fractures between 6
and 17 Ma, making this the youngest continental fl ood basalt province on Earth.
Columbia River fl ood b asalts
created by multiple pulses of heterogeneous mantle - derived
magmas, contaminated by continental crust
during magma ascent and magma mixing
produce a wide array of
rocks that include alkalic basalt as well
as alkaline and silicic rocks. Alkaline rocks
include phonolite, trachyte and lamproite.
Silicic rocks include rhyolite and rhyodacite,
which occur in lava domes or as pyroclastic
fl ow and ash fall deposits. Plutonic rocks vary
from syenite and alkali granite to gabbroic
rocks. Upwelling of hot plumes generated by
the return convective loop of downgoing
oceanic lithosphere.
* Partial melting at great depths of overthickened continental lithosphere following supercontinent assembly.
* Subduction of ocean spreading ridges
resulting in shallow sub - lithospheric
melting producing backarc basin type
extension within the continental
lithosphere.
Continental r ifts 1.1 Ga Keweenaw rift of the Lake Superior
basin (USA
The widespread occurrence of basalt and rhyolite without signifi cant andesite is referred to
as occurs at continental rifts and
hotspots underlying continental lithosphere.
Partial melting of the mantle generates basaltic magma.
bimodal volcanism
recognized three
immense rhyolitic lava deposits at Yellowstone ’ s silicic large igneous province
2.1 Ma Huckleberry Ridge Tuff, the 1.3 Ma
Mesa Falls Tuff and the 640,000 - year - old
Lava Creek Tuff. Together, these three tuff
deposits constitute the Yellowstone Group.
The Huckleberry Ridge eruption dispersed
2450 km 3
rhyolite deposits over an area of
15,500 km 2
and produced a caldera over
75 km long. The Mesa Falls eruption
produced tuff deposits largely within the
Huckleberry Ridge Caldera. While the Mesa
Falls eruptive deposits were restricted to the
pre - existing caldera, a new 16 km caldera
developed along the northwest end of the
Huckleberry Ridge Caldera. The youngest
Lava Creek cycle of eruptive activity began
around 1.2 Ma and continued for approximately 600,000 years. The Lava Creek
eruption produced a large caldera and
scattered rhyolitic deposits over an area of
7500 km 2
.
Thus the Yellowstone Caldera is a composite caldera generated by three separate rhyolitic eruptive events. In the intervening time
between each of these rhyolitic eruptions,
basaltic lava also erupte
The smallest of Yellowstone ’ s three Quaternary eruptive events
released fi ve times more debris than the
massive
1815 Tambora (Indonesia) eruption.
are anorogenic bodies injected into stable continental
cratons at moderate depths develop by differentiation of eclogite – peridotite parent magmas
resulting in mineral segregation within a
pluton.
Layered b asic – u ltrabasic i ntrusions As with Alaskan - type intrusions, layered
basic – ultrabasc intrusions are highly valued
for metal deposits, particularly platinum
group elements (PGE) as well as chromium,
nickel and cobalt
Three of the largest layered intrusions on
Earth are the
Stillwater Complex in Montana,
the Bushveld Complex in South Africa and
the Skaergaard Intrusion in Greenland
Other
signifi cant layered intrusions include
Muskox Intrusion of the Northwest Territories (Canada), the Keweenaw and Duluth
Intrusion of Minnesota (USA) and the Great
Dike of Zimbabwe.
formed during the Keweenaw rift event, is a major undeveloped PGE source.
Plans are currently underway to begin mining
PGE in the
Duluth
Complex,
2.7 Ga a large,
layered basic – ultrabasic igneous intrusion in
the Beartooth Mountains of southwestern
Montana. exposed
along a northwesterly strike for a distance
of 48 km, with observable thicknesses up
to 6 km. formed when basic magma intruded metasedimentary rocks, is the fi nest exposed
layered intrusion in North America and contains economic deposits of platinum group
metals as well as chromium, copper and nickel
sulfi des The basal zone consists of norite,
harzburgite and bronzite - rich orthopyroxenite
layers. The ultramafi c zone consists of dunite,
harzburgite, bronzite - rich orthopyroxenite
and chromite - rich peridotite layers. The basal
and ultramafi c zones contain copper, chromium and nickel sulfi de ore deposits. The
upper banded zone consists largely of repetitive layers of alternating norite, gabbro,
anorthosite and troctolite and is enriched in
copper, nickel and PGE ore deposits
Stillwater Complex
South Africa ’ s 2.06 Ga massive laccolith or domal structure, is the
world ’ s largest layered igneous intrusion.
Extending over 400 km in length, up to 8 km
thick and underlying an area of 60,000 km 2
,
this complex contains a layered sequence of
basic and ultrabasic rocks, capped locally by
granite. Upper zone consisting of gabbro and
norite.
2 Main zone containing gabbro and
anorthosite.
3 Critical zone consisting of anorthosite,
norite and pyroxenite.
4 Basal zone consisting of orthopyroxenite,
harzburgite, dunite and peridotite. A
chromite horizon occurs at the top of the
basal series hosts the largest
reserves of vanadium, chromium and platinum group metals in the world. PGE are concentrated within what is referred to as the
Merensky Reef within the critical zone. Anorogenic granitic rocks capping the complex
contain tin, fl uorine and molybdenum formed through
differentiation processes accompanied by a
series of magmatic injections, resulting in a
massive laccolith or domal structure
Bushveld Complex
Whereas most layered ultrabasic – basic intrusions are Precambrian in age, Greenland ’ s
55 Ma youngest of
the great PGE - enriched intrusion opolith intrusion crops out along
Greenland ’ s eastern shores and offers exceptionally good exposures of layering formed
by differentiation and convective current
structures heralded as the fi nest
example on Earth of fractional crystallization,
displaying layered sequences of euhedral to
subhedral crystals as well as distinctive structures usually associated with sedimentary
beds
Skaergaard Intrusion
ultrabasic volcanic rocks found
almost exclusively in Archean ( >2.5 Ga)
greenstone belts. Greenstone belts are metamorphosed assemblages of green - colored
rocks that contain layers of ultrabasic and
basic rocks overlain by silicic rocks and sediments
elevated liquidus
temperatures of 1575 – 1800 ° C
Komatiites
consists of needle - like, acicular olivine, pyroxene
(augite and/or pigeonite) and chromite phenocrysts in a glassy groundmass
occurs in the upper parts of
komatiite fl ows or in the chilled margins of
sills and dikes where rapid quenching produced skeletal, acicular crystals
Spinifex texture
The
virtual absence of Phanerozoic komatiites
may be attributed to lower upper mantle temperatures which precludes the extensive
mantle melting required to produce ultrabasic melts. The only known Phanerozoic
( < 544 Ma) komatiites occur on
Gorgona
Island, Colombia, where 88 Ma komatiites
erupted as > 1500 ° C ultrabasic lava fl ows.
Gorgona Island, located 80 km west of
Colombia in the Pacifi c Ocean, is composed
largely of gabbro and peridotite
otable for the rare occurrence
of ultrabasic pyroclastic tuffs which record
explosive volcanism
komatiite metallic ore
e 2.7 Ga Yilgarn Craton
of Western Australia, the 3.5 Ga South African
Barberton region and the 2.7 Ga Canadian
Shield
recciated, magnesium - rich,
ultrabasic rocks that rapidly rise to Earth ’ s
surface via cylindrical diatremes (Chapter 8 )
from deep within the mantle The high volatile content
serves two primary purposes in that (1) it
lowers the melting temperature preventing
crystallization, and (2) it provides the propellant “ jet fuel ”to accelerate kimberlite magma
to Earth ’ s surface. eruptions form maar craters
(Chapter 9 ) thatlargely fi ll with brecciated,
contain the high pressure minerals pyrope garnet, jadeite pyroxene and
diamond, which are stable at mantle depths
> 150 km.
Kimberlite
gneous rocks
enriched in carbonate minerals such as calcite,
dolomite or ankerite –are important CO 2
energy sources propelling kimberlites up from
mantle depths shallow intrusive to volcanic rocks that contain >20% CO 3 minerals
such as natrolite, trona, sodic calcite, magnesite and ankerite as well as other minerals
such as barite and fl uorite. The origin of
carbonatite was a contentious issue prior to
the 1960 eruption of the Oldoinyo L ’ Engai
Volcano in Tanzania. Oldoinyo L ’ Engai
erupted unusually low viscosity pahoehoe
carbonatite lava at temperatures of ∼ 500 ° C form in stocks, dikes and cylindrical structures primarily at continental rift
Carbonatites
magnesium - rich, volatile - rich, porphyritic rocks containing mafi c
phenocrysts such as biotite, phlogopite,
amphibole, clinopyroxene and melilite. associated with kimberlites and
continental rift zones, but also occur as dikes
intruding granodiorite plutons at convergent
margin settings.
Lamprophyres
potassium - rich, peralkaline
rocks containing minerals such as leucite,
sanidine, phlogopite, richterite, diopside and
olivine. enriched in barium
( > 5000 ppm), lanthanum ( > 200 ppm) and zirconium ( > 500 ppm). relatively poor in CO 2 ( < 0.5 wt %). occur in areas of thickened lithosphere
that have experienced earlier plate convergence or rifting episodes.
Lamproites
are silicic
plutonic rocks that are not associated with
convergent margin tectonism include stable cratons, continental rifts, ocean islands and inactive, post -
collisional continental margins. 1.1 – 1.4 Ga following the
assembly of the mid - Proterozoic Columbia
Supercontinent. granitic intrusions are widespread in North America,
extending from Mexico to the Lake Superior
Signifi cant volume occur in Precambrian cratons
throughout the world. These mid - Proterozoic
granitoid rocks are remarkably similar in
age, composition and appearance, displaying
rapakivi texture
Peak Batholith in Colorado (USA), develop
from the partial melting of residual silicic
granulite rocks (Chapter 18 ) that had previously generated I - type granites
Anorogenic (A - type) granites
texture refers
to sodium plagioclase overgrowths on pre -
existing orthoclase crystals
Rapakivi
