Igneous Petrology Flashcards by Engr. Joed Bautista

the branch of geology that
focuses on the study of rocks and the
conditions under which they form

Petrology

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Thickness of oceanic crust

10 km

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crust the has a uniform stratigraphy

oceanic crust

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thickness of continental crust

20-90 km

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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

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crust that has a variable composition

continental crust

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seafloor spreading takes place along a divergent plate boundary. the planet’s largest magmatic system

mid-ocean ridges

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group of islands that forms from volcanic activity along a subduction zone

island arcs

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coastal region characterized by mountain building activity

active continental margins

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thinning process of the lithosphere, leading to the rupture of the continent and the formation of mid-ocean ridges

intercontinental rifts

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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)

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volcanic rock, usually basaltic, erupted in oceans away from tectonic plate boundaries

ocean island basalts

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bodies of rocks built up by central eruption

volcano

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one tectonic plate subducts under another. formed by back-arc spreading

back arc basins

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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

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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

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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)

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example of shield volcano

binintiang malaki of taal volcano

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example of a stratovolcano

mayon volcano

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example of complex volcano

taal volcano

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example of cinder cone volcano

smith volcano or mt. babuyan

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world’s largest caldera

Apolaki Caldera in Benham Rise

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intrusion that form when magma intrudes between
the rock layers, forming a horizontal or gently dipping sheet of igneous rock.

sills

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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

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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