METAMORPHIC PETROLOGY (NON-FOLIATED METAMORPHIC ROCKS) Flashcards
1
Q
Composition of met rocks are determined by
A
Protolith chemistry
2
Q
Refers to the size, shaper, orientation and intergranular relationships of the rock’s constituens
A
Texture
3
Q
geometrical arrangement of grains
A
fabric
4
Q
Texture inherited from protolith
A
Relict Texture
5
Q
Inequant grains which one axis is significantly shorter that the other two axes and has a disc shaped pancake or paper-like shape
A
Tabular
6
Q
Grains in which one is significantly longer than the other two which are not equal
A
Bladed
7
Q
Grains in which one is significantly longer than the other two which are equal
A
Acicular
8
Q
Cigar-shaped
A
Prolate
9
Q
Grain size of aphanitic
A
<1mm
10
Q
Phaneritic Gran size
A
> 1mm
11
Q
Large relict grains from the protolith which has undergone deformation but still retains its orig composition.
A
Porphyroclasts
12
Q
Common Porphyroclasts
A
Qtz and Felds
13
Q
Oval-shaped feldspar porphyroclasts that resemble the shape of an eye and common in gneisses
A
Augen
14
Q
Oval shaped quartz porphyroclasts
A
Flaser
15
Q
Large grains that have experienced neocrystallization and growth in response to favorable T&P Conditions during metamorphism
A
Porphyroblasts
16
Q
growth of new minerals stable at the temperature and pressure conditions of metamorphism
A
Neocrystallization
17
Q
Common porphyroblasts
A
Garnet,
Staurolite,
Cordierite
18
Q
occurs when no preferred orientation of inequant grains is visible
A
Random Grain Orientation
19
Q
occurs when equant grains are oriented sub-parallel to one anther and can produce lineation and foliations
A
Peferred Grain Orientation
20
Q
Linear like features similar to pencils all point to a common direction which is commonly formed by preferred orientation of acicular, bladed, or rod-like grains with sub-parallel long axes
A
Lineations
21
Q
Minerals which are usually acicular, bladed or rod-like
A
Inosilicates
22
Q
Metamorphic layers oriented parallel to one another like pages in a book formed from the Preferred Grain orientation of tabular grains with subparallel long axes
A
Foliations
23
Q
Minerals which are usually tabular and produce foliations
A
Phyllosilicates
24
Q
What kind of stress produce random grain orientation?
A
Uniform Stress
25
Lineations and foliations are produced by
Non uniform stresses
26
Rock category in which crystals lack a preferred orientation
Non Foliated
27
Rock category in which crystals possess a preferred orientation
Foliated
28
What kind of metamorphism usually produce non foliated rocks?
Contact or Burial
29
What happens in such metamorphism
Uniform lithostatic stress produces equant or randomly arranged minerals so that prominent foliated textures arent produced
30
a fine grained <1mm diamter non forliated fabric thatd evelops by contact metamorphism
Hornfelsic texture
31
Met rock with fine grained non foliate fabric usually derived from fine-grained protolith rocks such as shale, mudstones, tuff or basalt
Hornfels
32
Characteristics of Hornfels
1) mostly equant crystals
2) Random grain orientation
3) Can preserve relict sed fabrics such as beddings
33
Where do hornfels usually develop?
Metamorphic Aureoles adjacent to intrusions (Contact met)
34
Common minerals of Hornfels
Musc
Biot
Andal
Cord
Plag
kfelds
Epid
Amph
Pyx
35
Hornfels is __________ and ___________ than mudstone
Harder and more brittle
36
Characterized by large equant grains (>1mm) or large inequant crystals that lack preferred orientation
Granoblastic Texture
37
High grade rocks with such texture that form at elevate T&P considitions associated with deep BURIAL
Granulite
38
Shapes of crystals in Granoblastic textures
Anhedral wth sutured boundaries
39
What is the implication of such GrainShape
combination of
Pressure Sol'n
Recyrstallization
Annealing
40
a strain recovery process in which new unstrained, polygonal grains develop from and replace highly strained grains at high T
Annealing/Polygonization/Hot Working
41
Usual crystals/Minerals with Granoblastic textures
Qtz
felds
calc
(Crystals with low euhedral form potential and usually in subequant forms)
no phyllosilicates or tabular to prismatic minerals
42
A common met granoblastic rock with >90% qtz which is hard, durable and produce angular surfaces when fractured
Metaquartzite
43
Usual protolith of Metaquartzite
qtz-rich sandstone
chert
44
Common accessory minerals in qtzite
Hemat
Felds
45
What processes are involved in the formation of Metaquarztie
Recyrstallization
Pressure soln
Intercrystalline plastic deformation
46
Usuall appearance of metaquartzite that distinguishes it from granular quartzarenite
smooth and glazed appearance
47
Uses of quartzite
Rock walls, railroad ballast and dranaige culverts
48
Granoblastic met rocks rich in calcite and dolomite derived by recrystallization of limestone or dolostone protoliths
Marble
49
types of metamorphism which produces marble
Dynamothermal
Deep Burial, or
contact
50
Common accessory minerals which provde distinctive hues to marble
Graphite
Ca and Mg-rich minerals
Brucite, Diops ,Forste
Wollas, Epid, Serpentine, Idiocrase,
Temolite, Grossular
51
What colors can an iron oxide mineral give to a marble
Red or Yellow
52
Characteristic of marbles
Soft and Easy to Cut
53
Granoblastic calc-silicate rocks formed by contact metamorphism of cabonate country rocks such as limestone or dolostones
Skarn
54
Another term for Skarns
Tactites
55
process responsible for the exchange of constituents between the pluton and the country rock
Metasomatism
56
Usuall mineral assemblage of skarn
Calc, dolo, Ankerite, qtz
and calc-mg silicates
57
Met rocks whith fractures, angular partices that forms in response to the brittle crushing of grains during deformation
Cataclastic rocks
58
in which environment are cataclastic rocks form
Upper Crustal Fault Zone within 15 kms of Earth's surface
59
What type of metamorphism form cataclastic rocks
Dynamic met
60
how are cataclastic texture described
with respect to:
relative percentages of Large Clasts and fine matrix
degree of cohesion
61
Cataclastic rocks that
lack cohesion
coarse angular fragment >2mm
Breccia
62
cataclastic rocks that
lack cohesion
fine grained
Gouge
63
Derived from metamorphism of sed or ign breccias commonly developed during dynamoyherma or dynamic met which contain subangular to angular clasts with >2mm.
Grains are interlocked tighlty that rupture occurs through grains
Metabreccia
64
Cohesive met rock with cataclastic textures produced by brittle deformation
Cataclasite
65
Conditions at which cataclasite forms
Low Temp
High Strain
Dynamic Met Conditions
at Upper Crustal Fault Zones
66
the ability to remain as a cohesive mass during deformation
Primary cohesion
67
cataclasite with 10-50% matrix
Para-cataclastite
68
cataclasite with 50-90% matrix
Cataclasite
69
catactasite with 90-100% matrix
Ultracataclasite
70
some facts about cataclasite
Serve as seals in faults zones
ruptures easily during fault reactivation
71
glassy rocks produced by high strain rates generating LOCALIZED metling due to pressure release in fault zones
very dark-colored vitreous to flinty which occurs as vein material
Pseudotachylite
72
High Strain Cataclastic Rocks created by SHORT TERM stresses associated with extraterrestrial bodies impacting the Earth
Impactites
73
Produced by fragmentation of rock upon impact
Impact Breccia
74
Glassy spherules that form as rocks are locally melted due to impact
Tektites
75
Form due to the intense stress that deform crystal structures especially common in "shocked"
Deformation lamellae
76
Ultra high pressure mineral assemblages such as high-P silca
Coesite
Stishovite
77
where was coesite first discovered?
Meteor crater
78
What are the four components of impactites
1. Impact Breccia
2. Tektites
3. Deformation Lamellae
4. High PressureMinerals Assemblages
79
Non-crystalline, high grade coals that form by heating, compression and chemically altering bituminous coal
Anthracites Coals
80
Diagnostic properties of AC
Vitreous
Lt. weight
Jet Black color
Conchoidal Fracture
81
Which have higer thermal capacity due to loss of volatiles?
Anthracite
82
derived from conglomerate protoliths with sub-rounded to rounded relict clasts with >2mm diameters
Metaconglomerate
83
Met associ with metaconglo
Deep Burial
Dynamothermal
Contact
84
Where does rupture occur in an otherwise tightly interlocking grains
within or through grains rather than around them
85
One type of clast conglo
Oligomictic
86
Many clast types
Polymictic
87
Metamorphism of conglo or breccias in response to STRONG NONUNIFORM Stresses during dynamic or dynamothermal metamorphism in which pebbles and cobbles are shorthened or flattend to the Z-strain direction and elongate to the X-strain in which pebble alignment may define lineation or foliation
Stretched Pebble Metaconglomerates
88
Serpentine rich met rocks that occur in foliated and non-foliated form
Serpentinite
89
process by which serpentinites form
Serpentinization
90
How does serpentinization proceed
at temperatures below 500 deg cel, ultrabasic rocks, Oli and pyx are HYDRATED to form serpentine group of minerals
91
Low temp serpentine minerals
Lizardite and Chrysotile
92
High Temp mineral
Antigorite
93
Environments of Serpentinization
1. Ocean Spreading Ridges
2. Subduction zones
94
chaotic assemblage or rocks in subduction complexes
Tectonic Melanges
95
Fine grained rocks that through alteration of ultrabasic rocks, or Mg-rich Sed rocks such as Dolostone by low temp and low pressure HF
Soapstones
96
Mineral assemblage of soapstone
Talc w/ Magnesite, Serpentine and/or Tremolite
97
Chacracteristic of Soapstone
Low Hardness
Wt. to green Color
Soapy Texture due to talc
98
Green colored rocks rich in silicate minerals that commonly include in Chlorite, Epidote, Prehnite, Pumpellyite Tack, Serpentine, Actinolite and Albite
Greenstones
99
Temp of alteration of basic and ultrabasic rocks to greenstones
200-500 deg cel
100
What minerals are being altered during metamorphism to form greenstnone
Plag
ferromag (Oli, Pyx, Amph)
101
What are the usual protoliths of Greenstones
Basalt and Gabbros
102
Type of Met
Hydrotherma Metamorphism
103
usuall site of greenstone formation
Oceanic crust near divergent plate boundaries
104
Na-rich basalt
Spilites
105
Na-rich andesite
Keratophyres
106
Large scale formation made up of greenstones usually of precambrian age and are synclinal
Greenstone Belts
107
Usual sequence of Greenstone belts (T to B)
1Greywacke and Chert
2Intemediate and silicic metavolcanic and metavolcaniclastic sequences
3metabasalt
4Komatiites ultrabasic metavolcanic rocks
108
This usually forms parallel greenstone belts and are granitic to dioritic composition metamorphosed at high T and Ps
Granulite Belts
109
Best known greenstone localities in the world
Barberton Belt, SA
Eastern Goldfields W.Australia
Superior and Slave Provnices Nam
Sao Francisco Craton Brazil
110
whats the implication of higher geothermal gradient during precambrian in subduction zones?
Higher grade metamoporhism at shallow depths and prevented deep subduction along steeply inclined benioff znones
111
Dark-colored rocs composed largely of amphiboles such as horblende and plagioclases
Amphibolite
112
Common Major mineral in Amphibolite
Garnet
113
Temp of formation of amphibolites during Regional Metamorphism (orogeny) of igneous rocks or sed rocks such as calcareous mudrocks and greywackes
>550 deg cel
114
Amphibolites with Basalt and Grabbro Protolith
Ortho-Amphibolites
115
Amphibolites with Sed protolith
Para-Amphibolites
116
Medium to coarse grained rocks with granoblastic to foliated texture
Granulite
117
high temp at which granulites are formed
>800km
118
High pressure conditions at which granulites form
>10Kbar approx 33km
119
Whats the implication of high temp metamorphism
Dehydration of hydrous amphibole and mica to pyx, kfeds, kyanite and garnet
120
what preserves the rocks' metamorphic fabric
High Pressure
Low Water content
121
Possible protoliths of Granulite
Gabbro
Peridotit
Pelitic Rocks (Mudstones, graywacke)
122
With increasng temp what mineral transformation has been observed withing granulites
opx and plag transforms to Qtz, Cpx, garnet
123
Very high pressure and high temp met rocks developed principally from basalt and gabbro protoliths
Eclogites
124
In what part of the earth is eclogite may be a major rock type?
Earth's Lower Crust
125
T andP of Eclogite formation
>400 deg cel
>1.2 Gpa >40km
126
Main mineral assemblage of Eclogite
Jadeite (Na,Al), Omphacite (Na,Ca) - Pyx
Garnet: Pyrope, Almandine, grossular
127
Processes which may form Eclogite
1) High P crystallization of deep contnental crustal rocks duing thickening at continent-continent collision
2) Partial Melting of the mantle followed by deep crystallization as high pressure eclogite
3) High P Met of subducted oceanic lithosphere deep within the earth
128
Density of Eclogite which may be the driving force of mantle convection and plate motion
3.5-40 g/cc
