Igneous Petrology (intro) Flashcards
Known as “primary rocks” that originated from solidified magma or lava.
Igneous rock
Known as “secondary rocks” which formed as a result of lithified fragments of pre-existing rocks.
Sedimentary
Rocks that formed as a result of pre-existing rocks undergoing metamorphism due to being subjected to heat, pressure, and fluids.
Metamorphic
rock that consists of multiple crystals of a single mineral.
Monomineralic rock
A rock that consists of multiple types of minerals and/or mineraloids.
Polymineralic rock
A model showing the origins, relationships and processes between rock types and other geologic materials.
Rock cycle
A model showing the origins, relationships and processes between rock types and other geologic materials.
Rock cycle
Magma is generated by
Partial melting
contains liquids, crystals, gases, and rock fragments in varying proportions depending upon temperature, pressure and chemistry conditions.
Magma
Magma that rises and erupts onto the surface of Earth.
Lava
The liquid portion of the magma.
Melt
The gaseous portion of the magma (H20, COz, S, Cl, F).
Volatiles
The solid portion of the magma.
Crystal
The processes were the magma or lava looses its heat and crystallizes.
Crystallization
Rocks that formed as a result of crystallization of magma or lava
Igneous rocks
Igneous rocks that formed beneath the surface as a result of loosing mobility.
Plutonic rock
Other name for intrusive igneous rock
Plutonic rock
Will tend to have larger crystal sizes as they have time to grow.
Plutonic rocks
Igneous rocks that solidified at the surface as a result of extrusion.
Extrusive rock
Will tend to have smaller crystal sizes as they rapidly cool and crystallize from the cooler environment.
Volcanic rock
The process where your pre-existing rock is heated to the point of partially melting.
Partial melting
The partial melting within the Earth’s crust.
Anatexis
When magmas that were generated by some other mechanism intrude into cold crust, they bring with them heat. Upon solidification, they lose this heat and transfer it to the surrounding crust
Temperature increase
Increase of temperature with depth
Geothermal gradient
Known as adiabatic melting
Decompression melting
occurs as a result of decrease in pressure in the system.
Decompression melting
Where do decompression melting occur
Divergent plate boundaries
Agents that reduces melting temperature of a substance.
Flux
The presence of volatiles in rocks acts as fluxes, weakening the bonds of atoms in the minerals, such as the Si-o bond, making them easier to melt.
Addition of volatile
Where do addition of volatiles usually occur
Subduction zone
Occurs when crystallization along the walls of the magma chamber in which crystals
preferentially form and adhere to the edges.
Marginal accretion
Includes fractionation processes that occur when crystals develop with significantly different densities than the surrounding magma.
Gravitational separation
A process during fractional crystallization where the first dense minerals that mineralize SINK and accumulate at the BOTTOM of the magma body.
Crystal settling
process during fractional crystallization where the first lighter minerals that mineralize FLOAT and accumulate at the top of the magma body.
Crystal floatation
process during magma cooling that occurs when the magma body is subjected to stress, squeezing off the melt from the magma body,
Filter pressing
Occurs whereby liquids
and crystals are segregated due to factors such as velocity, density or temperature.
Convective flow segregation
Two or more dissimilar magmas
coexist but retaining their distinctive characteristics.
Magma mingling
Thorough mixing of two or more magmas,
with the individual characteristics no longer recognizable.
Magma mixing
Thorough mixing of two or more magmas,
with the individual characteristics no longer recognizable.
Magma Mixing
The incorporation and digestion of solid or fluid foreign materials, such as the wall rock.
Magmatic assimilation
Inclusions in magmatic bodies.
Xenolith
One parent magma fractionates to produce two or more distinctly different daughter
magmas with different compositions.
Liquid fractionation
Involves the selective diffusion of ions in the magma due to compositional, thermal or density gradients, and water content,
Differential diffusion
Also known as liquid-liquid fractionation,
Liquid immiscibility
separation of magma into two
or more distinct immiscible liquid phases.
Liquid immiscibility
A graphical method used to discriminate samples through their chemical content into correctly identifying an igneous rock.
Variation diagram
Igneous rocks that are dominantly composed of dark-colored silicates, but can commonly appear green,
Ultramafic
These are major constituents of ophiolites and mantle.
Ultramafic
Igneous rocks that are dominantly composed of dark-colored silicates, such as pyroxenes,
plagioclase and amphiboles.
Mafic
These are major constituents of oceanic crusts.
Mafic
Also called as basaltic
Mafic
Igneous rocks that are gray-colored to salt-and-pepper, depending on the size of the mineral grains.
Intermediate
These are major constituents of volcanic arcs.
Intermediate
Igneous rocks that are dominantly composed of light-colored silicates, such as quartz and feldspars.
Felsic
These are major constituents of continental crust.
Felsic
A direct type of classification
of composition that
involves visual comparison of minerals and
determining their volume percentages.
Modal classification
indirect type of classification of composition that analyzes the chemical composition of rocks.
Normative classification
SiO2% content of ultrabasic
Less than 45
SiO2% content of basic
45 - 52%
SiO2% content of intermediate
52-63%
SiO2% content of acidic
66%
A volcanic Ultramafic rock
Komatiite
A plutonic ultramafic rock.
Peridotite
A plutonic mafic rock
Gabbro
A volcanic mafic rock.
Basalt
A plutonic, salt and pepper colored rock
Diorite
A volcanic, gray colored rock
Andesite
A plutonic, light-colored (felsic) rocks, containing approximately two-thirds SiO2
Granodiorite
A volcanic, light-colored (felsic) rocks, containing approximately two-thirds SiOz,
Dacite
A plutonic, light-colored (felsic) rocks containing more than two-thirds SiO, (silicic or acidic)
Granite
A volcanic, light-colored (telsic) rocks containing more than two-thirds SiO, (silicic or acidic)
Rhyolite
Light-colored, felsic, frothy, vesicular rock.
Pumice
Dark-colored, mafic, frothy, vesicular rock.
Scoria
A dark-colored, silicic, non-crystalline igneous rock that has a glassy texture.
Obsidian
A dark-colored, basic, non-crystalline igneous rock that has a glassy texture.
Tachylite
INTRUSIVE IGNEOUS STRUCTURES (IIS):
Plutons of more or less irregular shape with surface exposures ≥ 100 square kilomemetres.
Batholith
INTRUSIVE IGNEOUS STRUCTURES (IIS):
Plutons with surface exposures ≤ 100 square kilometres.
Stocks
Intrusive Igneous Structures: Concordant Plutonic Structures
A tabular, concordant pluton that parallels the country rock.
Sill
Intrusive Igneous Structures: Concordant Plutonic Structures
A dome-like concordant pluton characterized by a dome roof and flat floor.
Laccolith
Intrusive Igneous Structures: Concordant Plutonic Structures
A dish-shaped concordant pluton that has a “champagne glass” appearance in a section view.
Lopolith
Fractured rocks along a magma chamber’s wall.
Stopes
Consists of genetically-related magmas with a composition that evolved from a common, original, parental magma.
Magma Series
Record a progressive decrease in iron and magnesium with increasing SiO₂, and alkali concentrations due to the early crystallization of ferromagnesian minerals, hence, an enrichment in alkaline minerals.
Produce largely andesites, dacites, rhyolites, and high-alumina basalts (BADR).
Dominantly occurs along convergent margin environments with volcanic arcs and subduction zones.
Calc-Alkaline Magmas
Experience enrichment in iron at low to moderate SiO2 concentrations with increasing fractionation due to depleted MgO and CaO from early crystallization of forsterite olivine and Ca-plagioclase.
Produce large volumes of basalt with little variations in composition.
Dominantly occurs extensional environments such as ocean ridges and continental rifts, and some hotspots in intraplate settings and immature arcs in thin volcanic arc crusts.
Tholeiitic Magmas
Magmas that are less common than calc-alkaline or tholeiitic magmas, highly enriched in Na₂O and/or K₂O and contains an extremely diverse compositions that have SiO₂ contents ranging from 0-65%.
Occurs in a wide variety of environments that include stable cratons, continental rifts and subduction zones.
Alkaline Magmas
Characterized by high concentrations of silicic and basic rocks, with little intermediate rocks, and associated with continental rifts.
Its basic component is derived from partial melting of the mantle, while its silicic component is derived from the partial melting of the continental crust from the heating of the rising basic magmas.
Bimodal Magma Suites
