MindMap Gallery Igneous Petrology
- 19
Igneous Petrology
Igneous petrology is a branch of geology that focuses on the study of igneous rocks, their formation, composition, and properties. It involves the analysis of the processes that lead to the formation of igneous rocks from magma, as well as the classification and identification of different types of igneous rocks. This visual representation can provide a comprehensive overview of the key concepts and principles in igneous petrology, making it a valuable tool for students, researchers, and geology enthusiasts.
Edited at 2021-11-15 08:47:28
- Recommended to you
- Outline
Igneous Petrology
Source rock
Increase temperature
Decrease pressure
Add water
Melting
Magma
Melt
Whole-rock composition
Crystals
Phenocrysts
Gas bubbles
Vesicles
Crystallisation
Igneous product
Classification
Grain size
Aphanitic
Extrusive rock
Chemical composition
Acidic
Rhyolite
Intermediate
Andesite
Basic
Basalt
Ultrabasic
Komatiite
Phaneritic
Intrusive rock
Colour index
Felsic
Granite
Intermediate
Diorite
Mafic
Gabbro
Ultramafic
Peridotite
Resultant igneous rock
MASH
Granite
Mineral definition
Quartz
Framework silicate
Alkali feldspar
Framework silicate
Sodic plagioclase
Framework silicates
Anhydrous minerals
Type minerals
Hornblende
Double-chain slicates
Biotite
Sheet silicates
Muscovite
Sheets silicates
Hydrous minerals
High viscosity
Not easy to be transported
More storage time for magma
Assimilation and fractional crystallisation (AFC) are significant
Check Crystallisation
Magma differentiation controlled by AFC
Check Melting
Phenocrysts could be formed during the magmatic process or post-magmatic process as well
Solidified easily once pressure release
Forming granite in-situ
Granitisation
Obsolete idea
Migmatisation
Partial melting of deep crustal rocks (often sedimentary)
Melt
Leucosome
Restite
Melanosome
Solidified before it migrate to any significant distance
Local decompression
Forming granite with migration (H2O undersaturated)
Stopping
Cauldron subsidence
Diapiric upwelling
Ballooning
Dyke feeding
Magmatic texture
Igneous layering
Multiple phases of injection
Veins and dykes
Magma mingling
Enclaves
Water-rich environment
Low crystal nucleation rate, but high crystal growth rate
Pegmatite
Alteration
Hydrolysis
Mineralisation
Porphyry Cu-Mo
Sn-W-Mo
Au-Ag veins
Chemical composition
Major elements (oxides in wt%)
CIPW Norm
Loss-on-ignition
ASI > 1.0
Peraluminous
ASI > 1.1
S-type granite
Derived from sedimentary source
ASI < 1.0 and Na2O + K2O < Al2O3
Metaluminous
ASI < 1.1
I-type granite
Derived from igneous source
ASI < 1.0 and Na2O + K2O > Al2O3
Peralkaline
Usually A-type granite
Forming in anorogenic environment
Trace elements (in ppm)
Trace element geochemistry (Spidergram)
Normalisation
Primitive mantle
Mid-ocean ridge basalt (MORB)
Chondrite
Compatible elements
Stay in the minerals (source of melting)
Incompatible elements
Go to the melt
Large-ion lithophile elements (LILE)
High field-strength elements (HFSE)
Water
Abundant of water
Water can come from subduction and hydrous minerals of the source
High Rb, low Y + Nb
Collision granite (COLG)
Less water
Relatively Low Rb, low Y + Nb
Volcanic arc granite (VAG)
Recycled subducted crustal materials, less water
High Rb, high Y + Nb
Within plate granite (WPG)
Fractionated from anhydrous basaltic source
Low Rb, high Y + Nb
Ocean-ridge granite (ORG)
Boninites
Chemical composition
Trace elements (in ppm)
Trace element geochemistry (Spidergram)
Normalisation
Primitive mantle
Mid-ocean ridge basalt (MORB)
Chondrite
Compatible elements
Stay in the minerals (source of melting)
Incompatible elements
Go to the melt
Large-ion lithophile elements (LILE)
Water-rich environment / Recycled subducted crustal materials from deeper mantle
Enrichment
High field-strength elements (HFSE)
Relatively stable in water
Shallow U-shape REE pattern
Extreme depletion, especially in Ti, but positive Zr anomaly
Extraction from source experienced multiple extractions
Adakites
Chemical composition
Major elements (oxides in wt%)
CIPW Norm
Loss-on-ignition
SiO2 >= 56% and Na2O >= 3.5%
Mg# 45-60
Originated from partial melting of basaltic source rather than peridotite
Trace elements (in ppm)
Trace element geochemistry (Spidergram)
Normalisation
Primitive mantle
Mid-ocean ridge basalt (MORB)
Chondrite
Compatible elements
Stay in the minerals (source of melting)
Incompatible elements
Go to the melt
Large-ion lithophile elements (LILE)
Water-rich environment / Recycled subducted crustal materials from deeper mantle
Enrichment in Sr
High field-strength elements (HFSE)
Relatively stable in water
Depletion in Nb, P, and Ti Nb depletion tend to be the same P and Ti depletion increases with magma acidity
Sr/Y > 40
Source rock contains garnet
Al-rich source, usually representing sedimentary crustal signature
Slab melting
Andesite, dacite, rhyolite
Andesite
Mineral definition
Plagioclase
Framework silicate
One or more mafic minerals
Dacite
Mineral definition
Sodic plagioclase
Framwork silicate
Quartz
Framework silicate
Rhyolite
Mineral definition
Quartz
Framework silicate
Alkali feldspar
Framework silicate
Anhydrous minerals
Type minerals
Biotite
Sheet silicate
Hornblende
Double-chain silicate
Hydrous minerals
Oxidising conditions
Calc-alkaline trend
High viscosity
Not easy to be transported
More storage time for magma
Assimilation and fractional crystallisation (AFC) are significant
Check Crystallisation
Magma differentiation controlled by AFC
Check Melting
Phenocrysts could be formed during the magmatic process or post-magmatic process as well
Solidified easily once pressure release
Chemical composition
Major elements (oxides in wt%)
CIPW Norm
Loss-on-ignition
K2O increases with vertical depth of the Benioff zone beneath the arc
Increases from trench to back-arc
Trace elements (in ppm)
Trace element geochemistry (Spidergram)
Normalisation
Primitive mantle
Mid-ocean ridge basalt (MORB)
Chondrite
Compatible elements
Stay in the minerals (source of melting)
Incompatible elements
Go to the melt
Large-ion lithophile elements (LILE)
Water-rich environment / Recycled subducted crustal materials from deeper mantle
Enrichment in Rb, Ba, Th, K, and Sr
High field-strength elements (HFSE)
Relatively stable in water
Depletion in Nb, P, and Ti Nb depletion tend to be the same P and Ti depletion increases with magma acidity
Rb/Yb increases with magma acidity
Subduction-related
Komatiite
High temperature melting at 1500-1600 degrees
Formed in Archaean when the Earth is hotter
Found along greenstone belts
Peridotite
Mineral definition
Olivine
Isolated silicate
Clinopyroxene
Single-chain slicate
Orthopyroxene
Single-chain silicate
Anhydrous minerals
Low viscosity
Ready to be transported
Less storage time for magma
Assimilation and fractional crystallisation (AFC) are not significant
Check Crystallisation
Magma differentiation controlled by partial melting
Check Melting
Phenocrysts represent the source of previous magmatic events
Ultramafic cumulates in layered intrusion
Representing mantle
Check Mg# of olivine in mantle xenoliths
Olivine Mg# can tell how primitive the mantle source is
Primary melt with mantle signature will have Mg# 68-77
Alteration
Serpentinisation
Gabbro
Mineral definition
Calcic plagioclase
Framwork silicate
Augite (Clinopyroxene)
SIngle-chain silicate
Anhydorus minerals
Magmatic texture
Igneous layering
Modal layering
Variation of relative proportion of cumulus minerals with structural height of pluton
Gravitational sorting
Crystal nucleation efficiency
Phase layering
Appearance or disappearance of cumulus minerals with structural height of pluton
Reaction between intermediate products and the intermediate melt in the phase diagram
Cryptic layering
Systematic variation in the chemical composition of cumulus minerals with structural height of pluton
Layered intrusion
Platinum group elements (PGE) mineralisation
Chromite
Crystallisation
Equilibrium crystallisation
Theoretical
Fractional crystallisation
Product can be different from the melt
Intermediate product during crystallisation can react with intermediate melt to form new product
Seperation of intermediate product from the melting system
Variation diagrams
Discontinous series of Bowen's Reaction Series
Solid solution
Core-rim structure of minerals
Phase diagrams
Melting
Equilibrium melting
Theoretical
Fractional (partial) melting
Depth of melting
Extent of melting
Enrichment in incompatible elements
Refer to the petrogenesis of alkali igneous rocks and plume-related igneous rocks
Source material
Phase diagrams
Basalt
Mineral definition
Calcic plagioclase
Framework silicate
Augite (Clinopyroxene)
Single-chain silicate
Anhydrous minerals
Low viscosity
Flowing morphology
Subariel flow
Pahoehoe flow
A'a flow
Scoria
Subaqueous flow
Pillow lava
Sheeted flow
Low viscosity
Ready to be transported
Less storage time for magma
Assimilation and fractional crystallisation (AFC) are not significant
Check Crystallisation
Magma differentiation controlled by partial melting
Check Melting
Phenocrysts represent the source of previous magmatic events
Chemical composition
Major elements (oxides in wt%)
CIPW Norm
Loss-on-ignition
Silica-oversaturated
Silica-saturated
Tholeiite
Silica-undersaturated
Alkali basalt
Trace elements (in ppm)
Trace element geochemistry (Spidergram)
Normalisation
Primitive mantle
Mid-ocean ridge basalt (MORB)
Chondrite
Compatible elements
Stay in the minerals (source of melting)
Incompatible elements
Go to the melt
Large-ion lithophile elements (LILE)
Water-rich environment / Recycled subducted crustal materials from deeper mantle
Enrichment
Subduction-related
Plume-related
Depletion
Oceanic ridge-related
High field-strength elements (HFSE)
Alteration
Serpentinisation