Igneous Petrology Flashcards
the branch of geology that
focuses on the study of rocks and the
conditions under which they form
Petrology
Thickness of oceanic crust
10 km
crust the has a uniform stratigraphy
oceanic crust
thickness of continental crust
20-90 km
are large, basin-like depressions
formed when a volcano erupts and
collapses. They can host secondary volcanic
features such as lava domes and smaller
craters
caldera
crust that has a variable composition
continental crust
seafloor spreading takes place along a divergent plate boundary. the planet’s largest magmatic system
mid-ocean ridges
group of islands that forms from volcanic activity along a subduction zone
island arcs
coastal region characterized by mountain building activity
active continental margins
thinning process of the lithosphere, leading to the rupture of the continent and the formation of mid-ocean ridges
intercontinental rifts
are large, steeply-sloped volcanoes built from alternating layers of lava flows, ash, and other volcanic debris. They are known for their explosive eruptions
stratovolcano (composite volcano)
volcanic rock, usually basaltic, erupted in oceans away from tectonic plate boundaries
ocean island basalts
bodies of rocks built up by central eruption
volcano
one tectonic plate subducts under another. formed by back-arc spreading
back arc basins
have broad, gentle slopes and
are built by the flow of low-viscosity basaltic lava.
Their eruptions are typically less violent than those
of stratovolcanoes
shield volcano
are the smallest type of
volcano, formed from particles and blobs of
congealed lava ejected from a single vent. They
have steep slopes and typically erupt explosively
cinder cone volcano
consist of multiple
volcanic centers, including stratovolcanoes,
shield volcanoes, and cinder cones. These
structures form over long periods of volcanic
activity
complex volcano (compound volcano)
example of shield volcano
binintiang malaki of taal volcano
example of a stratovolcano
mayon volcano
example of complex volcano
taal volcano
example of cinder cone volcano
smith volcano or mt. babuyan
world’s largest caldera
Apolaki Caldera in Benham Rise
intrusion that form when magma intrudes between
the rock layers, forming a horizontal or gently dipping sheet of igneous rock.
sills
are large, deep-seated intrusions (sometimes called
Plutons) that form as thick, viscous magma slowly makes its way toward
the surface, but seldom gets there
batholiths
intrusion that form as magma
pushes up towards the
surface through cracks in
the rock. they are vertical
or steeply-dipping sheets of
igneous rock.
dykes
are mushroom-shaped bodies
with a flat floor and a domed roof. Thus, they
appear to have begun forming in the same way
as sills; however, as magma continued to
intrude, it pushed up the overlying layers rather
than continuing to spread out laterally
laccoliths
are smaller bodies that are likely fed from deeper level batholiths. It may have been feeders for volcanic eruptions, but
because large amounts of erosion are required to expose a stock or
batholith, associated volcanic rocks are rarely expose
stocks
: igneous intrusion associated with a structural basin,
with contacts that are parallel to the bedding of the enclosing
rocks. They can be several miles to several hundred miles in
diameter, with thicknesses up to several thousand feet, are some
of the largest igneous intrusions known
lopolith
lava that has a smooth, billowy or ropy surface
pahoehoe lava
a pluton parallel to the bedding plane
or foliation of folded country rock. More specifically,
it is a typically lens-shaped pluton that occupies
either the crest of an anticline or the trough of a
syncline
phacolite
are lava flows reaching the
surface of the earth along extensive fissures
fissure eruptions
lava that is composed of irregular blocks
that lack spines.
block lava
an extensive crack in a rock
fissure
cones that are built chiefly of
lava that was very fluid at the time of eruption
lava cones/shield volcano
composed of rock debris, boulders, and molten materials thrown out during volcanic eruption mixed with water
lahar
cones that are built chiefly of pyroclastic
material and may have very steep slopes.
pyroclastic cones
cones that are
built of alternating layers of lava and
pyroclastic material
composite cones/strato volcanoes
the smaller depression at the top
of a volcano and it is directly above the
conduit or pipe that feeds on the
volcano
crater
– the channel way/opening of a
volcano through which magma ascends to the
surface.
volcanic vents
are shallow and near-surface
intrusive that fall within the volcanic class,
which represents magma that has solidified in
the vents of eroded volcanoes or as tabular
sheets
plugs or necks
first volcanic plug in the Ph
Ilijan plug in tubigon, bohol
Magma originates from the ________ of
rocks in the Earth’s mantle or crust. this is the process by which only a portion
of a solid rock melts to form magma.
partial melting
are upwellings of
exceptionally hot and buoyant mantle material that originate from
the deep mantle
hot mantle plumes
refers to the increase in temperature with depth beneath the Earth’s surface
geothermal gradient
heating occurs due to the movement of rocks
along fault planes or during tectonic processes
frictional heating
refers to the movement of thermal
energy from hotter regions to cooler regions within the Earth’s
interior
heat transfer
Radiogenic heat is generated from the decay of
radioactive isotopes within the Earth’s crust and mantle
radioactivity
process of magmatic
differentiation whereby ascending
magmas evolve chemically by recruiting
easily melted or dissolved
components(fusible) from the walls of
their conduits.
assimilation
occurs when
magmas from different sources or
at different stages of evolution
combine, resulting in a magma
with a hybrid composition
magma mixing
the process
where different minerals crystallize out
of the magma at different
temperatures and settle out,
changing the composition of the
remaining liquid magma
fractional crystallization
process wherein As magma cools, mineral crystals begin to form
crystallization
a concept in
geology that explains the order in
which minerals crystallize from cooling
magma
bowen’s reaction series
degree of crystallization when a rock is composed entirely of crystals
holocrystalline
degree of crystallization when the rock is composed entirely of glass
holohyaline
degree of crystallization when the rock is composed of a mixture of crystals
and glass
merocrystalline
classification which classifies rocks on the basis of where they form
genetic
Formed from lava that cools and solidifies at
the Earth’s surface. These rocks typically have
smaller crystals due to the faster cooling rate
volcanic or extrusive
also known as subvolcanic or shallow
intrusive rocks, form from magma that cools and solidifies at medium depths, typically within the upper crust. The cooling process is intermediate, resulting in a texture that
is somewhere between plutonic and volcanic rocks.
Example: Dolerite (also called Diabase
hypabyssal
formed from magma that cools and solidifies
beneath the Earth’s surface. These rocks typically have larger crystals due to the slower cooling rate.
Examples: granite, diorite, gabbro
plutonic or intrusive
classification that refers to the
size, shape, and arrangement of
mineral grains.
textural
Coarse-grained texture
where individual minerals are visible to the
naked eye (e.g., granite)
phaneritic
Fine-grained texture where
individual minerals are too small to be seen
without magnification (e.g., basalt).
aphanitic
Which is basic: granite, andesite, basalt, peridotite
peridotite
Texture characterized by
large crystals (phenocrysts) embedded
in a fine-grained matrix (groundmass)
(e.g., andesite).
porphyritic
Texture with no crystals, as
the rock cooled too quickly for crystals
to form (e.g., obsidian).
glassy
Low in silica (45-52%), dark-colored,
and rich in iron and magnesium. Examples include
gabbro and basalt
mafic
Which is acidic: granite, andesite, basalt, peridotite
granite
Texture characterized by
the presence of cavities (vesicles)
formed by gas bubbles (e.g., pumice)
vesicular
Composed of volcanic
fragments ejected during an eruption
(e.g., tuff)
pyroclastic
classification
involves the analysis of the rock’s chemical
composition, particularly the silica (SiO₂)
content
chemical composition
color gradation
felsic-intermediate-mafic-ultramafic
High in silica (>65%), light-colored, and rich in quartz and feldspar. Examples include granite and rhyolite
felsic
gradation in silica content
acidic-intermediate-basic-ultrabasic
Intermediate silica content (53-65%), with moderate
color and mineral composition. Examples include diorite
and andesite
intermediate
Very low in silica (<45%), very dark
and dense, and composed mostly of olivine and
pyroxene. Examples include peridotite and komatiite
ultramafic
determine elemental concentration, trace
elements, and specific element analysis
AAS
rock classification that contains neither quartz nor an unsaturated mineral
saturated
determine elemental composition, concentration
of each element, and quantitative and qualitative
analysis
XRF
Al2O3 < (Na2O + K2O)
peralkaline
separate SiO4 groups in
which the tetrahedra are not linked
directly to each other but are bound
together by intervening cations
nesosilicate
groups in igneous rocks according to SiO2 saturation
saturated and unsaturated minerals
two most abundant component of igneous rock
SiO2 and Al2O3
rock classification that contains primary silica mineral
oversaturated
rock classification that contains unsaturated minerals
unsaturated
Al2O3 > (Na2O + K2O + CaO)
peraluminous
Al2O3 < (Na2O + K2O + CaO) but Al2O3 >
(Na2O + K2O)
metaluminous
Al2O3 = (Na2O + K2O)
subaluminous
Si2O7 may be considered
as a condensation of two silica
tetrahedra.
They are linked by a common oxygen
which serves as a bridging ion
sorosilicate
ring structures Si6O18 in
which the SiO4 groups are not
independent but are united through
common oxygen ions in the form of a
ring
cyclosilicate
continuous single chains of
tetrahedra each sharing two oxygens.
– continuous double chains of
tetrahedra sharing alternately two and
three oxygens.
inosilicate
continuous shells
of tetrahedra each sharing three
oxygens.
phyllosilicate
continuous
frameworks of tetrahedra each
sharing all four oxygens.
tectosilicate
are spherical bodies composed
of fibers of feldspar with radial arrangement
about a common center
spherulite
refers to rock riddled
with air bubbles which may be almond-shaped, rounded, ellipsoidal, or even tabular
vesicular structure
term applied to basaltic lava in
which the gas vesicles are numerous and
irregular in shape that is darker and denser than pumice
scoria
are small cavity formed in volcanic
rock by entrapment of a gas bubble during
solidification
vesicles
a frothy siliceous lava, produced in
an extreme stage of gas escaping
pumice
are infilling of vesicles by
secondary minerals such zeolites, carbonates
and various forms of silica
amygdules
a fined-grained or glassy base
groundmass
are large and well-shaped
crystals
phenocrysts
refers especially to a mass
of sanidine laths in subparallel alignments, like
a school of minnows
trachytic structure
contains large, prominent crystals in a deep-reddish fine-grained matrix
porphyritic structure
