IGNEOUS PETROLOGY (IGNEOUS ROCK ASSOCIATION) Flashcards by Sean Levi Abiera

Associations of rocks that form in response to similar geologic conditions

Petrotectonic Assoaciations

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How much of Earth’s magma is generated in each plate boundaries

Divergent 62%
Convergent 26%
Hotspot 12%

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Layer 1

Well Stratified Pelagic Sediments that accumulated on the ocean floor

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Layer 2

Pillow Basalts
Sheeted Diabase Dikes

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Layer 3

Massive Isotropic Gabbro
Layered Cumulate Gabbro
Layered Cumulate Peridotite

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Layer 4

Depleted Mantle Peridotite (Harzburgite, Dunite)

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What marks the Seismic moho?

between Cumulate Gabbro and Cumulate Peridotite
Based on seismic wave evidences

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most abundant volcanic rock on Earth

Mid Oceanic Ridge Basalts

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MORB that is strongly depleted with incompatible elements
and represents partial melting at 20-30% of depleted mantle source

Normal MORB (N-MORB)

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MORB that is enriched with incompatible elements
With smaller degrees of Partial Melting

Enriched MORB (E-MORB)

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Compare the Andesite and Rhyolite formed in Oceanic Ridges to those formed in convergent boundaries

?Hgiher TiO2
?Always subordinate to Basalt

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Factors that affects magma composition in Convergent Plate Boundaries

1) Composition and Thickness of Overlying Plate
Thin Ocean - Metaluminous
Thick Continental - Peraluminous
2) Composition of Rock Material being Melted
3) Flux Melting
4) Other Diversification Processes
5) Dip Angle of Subduction Zones
Cold Old Dense Lithosphere - Shallow Subduction
Young Warm Bouyant - Steeply Inclined Subduction zones

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Dominant Igneous Rocks Found in Convergent Plate Boundaries

Calc-Alkaline
Enriched in SiO2, K2O, Na2O, LIL, LREE (Incompatible)

Depleted in FeO, MgO, HFS and HREEs

> 3% Water (Hblde and Biotite)

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Calc Alkaline association that is the signature volcanic rock suite of convergent boundaries

BADR (Basalt, Andesite, Dacite, Rhyolite)

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Volcanic Rocks w/ 45-52% SiO2

Basalt

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Type of Basalt found in Convergent Boundaries that have higher Al2O3 content but are also enriched in Fe and low K2O

Arc tholeiites/High Aluminum Basalt

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Basalts found in convergent boundaries with higher alkali content K2O and do not have Iron Enrichment

Calc Alkaline Basalt

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Type of Andesites with 52-57% SiO2 and are found in Youthful Island Arc Systems

Basaltic Andesites

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Types of Andesites with 57-63% SiO2 and are found in more mature continental Arcs

Silicic Andesite

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What are the phenocrysts which may occur in Porhyritic Andesite

1) Plag (Euhedral and Zoned)
2) Hbld (Reactions Rims)
3) Pyroxene
4) Biotite

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Angle of subduction which favor generation of volumnous andesite

> 25 deg

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Quartz-phyric vlcanic rocks intermediate between andesite and rhyolite with 63-68% extending to 77% TAS Classification and are enricehed in palagicolases and Minor kfelds

Dacite

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Rocks composed of 66-69% SiO2 with limit at 57% SiO2 in TAS and commonly contain phenocrysts of ANDESINE to OLIGOCLASE amids a goundmass of ORTHOCLASE and AUGITE high K2O

Trachyandesite (Shoshonite and Latites)

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Volcanic Rocks with >69% SiO2 associated with explosve silicic eruptions

Rhyolites

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Volcanic Rocks with 68-73% SiO2 which can occur as glasses, pyroclastc tuffs and breccias

Rhyodacite(unofficial)

Rocks which dominates if the overlying slab thickness rangers from 0-20 km thin

Low K Tholeiites/Arc Basalts

Rocks which Dominates if the overlying slab thickness ranges from 20-40km moderate

Mod K Calc Alkaline Andesite

Rocks which Dominates if the overlyin slab thickness is greater than 40 (40Km) Thicker

High K shoshonites

Thickness and K-content

Thicker the overlying Slab the higher the K-content

Arrange representative rocks in increasing k-content

Arc Tholeiites Calc Alkaline Andesite Shoshonite

Three types of Convergent Margins with corresponding resultant tectonic landform

1) Ocean-Ocean - Youthful Island Arc 2) Ocean-Continental - Mature Continental Complexes 3) Cont-Cont Cessation of Subduction and Collision

Composition of Diorite

Plag, Hbld, <5%qtz

Composition of Qtz Diorite

Plag, Hbld, 5-20% qtz

Plutonic Equivalents of Rhodacites and dacites

Granodiorite (>20% Quartz)

Plutonic Rocks nriched in CALCIC PLAG and QTZ w/ minor Kfelds, Biotite and Hbld

Tonalite

Granodioritic rocks in which half to 2/3 of plag are SODIC PLAGIOCLASE

Trondhjehmites

IN which part of the volcanic arc are Low K Arc Tholeiites formed?

Oceanward nearest to the trench

High Magnesium intermediate Volcanic Rocks that contain SiO2 Saturated Groundmass

Boninites

Silica Saturated rocks known to be derived from the the melting of subducting Slab of the oceanic Lithosphere

Adakite

Relatively thin Lithosphere in Youthful volcanic arcs will form

Basalt Basaltic Andesites Boninite Adakite

Tholeiitic basalts that are more enriched in H2O, alkali Elements and LIL and are slighlty depleted in Ti, Y and Nb

Back Arc Basin Basalts (BAB)

Difference of Mature to Youthful island arc?

More Enriched in K2O and SiO2 due to thick overlying wedge

What types of plutons occur in Ocean-Continent Subduction?

Silicic (Granodiorite, Diorite, and Tonalite)

Volcanic Rocks in Ocean-continent subduction

Andesitic, Dacites, Rhyodacites, Rhyolties and Latites

Volcanic Rock that is darkcolored, K-rich trachandesite commonly containing olivine and augite phenocryst with labradorite plag, Kffelds, olviing, augite and leucite ground mass occrus in thick oceanic crust

Shoshonite

Type of granitic magma formed by partial melting of basic to intermediate igneous rocks in or above the subduction zone at ocean-ocean or ocean conv margins and are Mataluminous

I-type

Type of granitic magma which are peraluminous mostly found in continent-continent collisions an is dervied from phyllosilicate minerals in sed rocks such as graywackes and mudstone of the concrust and accretioary wedge

S-type

Granites derived from mantle derived parental magmas and are associated with calc-alkaline tonalites, Qtz Diorite and Gabbroic Rocks and are developed in Island Arc settings

M-Type

Mineralization in such type of granites

Cu and Au

Types of deposits associated with I-type

PCDs, Tungsten and Molybdenum

Types of deposits associated with S-Type

Tin Deposits

Anorogenic rocks produced by activties unrelated to subduction and collission and are more enriched in LIL elements and re mostly alkali rich

A-Type

Fault bounded, deformed rck sequence that mark the site of present or former convergent margins which may have been transprted far from their site of origin by thrust faulting

Alpine Orogenic Complexes

An intensely Sheared, heterogenous rock assemblage embedded within a highly deformed mud matrix

Melanges (Mixture))

A type of Alpine deposit in which the oceanic or back arc basin lithospher or volcanic arc basement are preserved in origenic belts which represents coherent slices of oceanic lithsphere, volcanic arc basement or back arc basin ltihosphere obudcted onto the edge of a subduction zones

Ophiolites

Ophiolites that represent oceanic fragments in either forearc aor back arc settinsg

Suprasubduction Zone Ophiolite (SSZ)

Consists of concentrically layered zoned plutons formed in convergent margin settings with a dunite core and pyroxenite shell and surrounded by massive gabbro

Alaska Type Intrusion

Deposits which are related to Alaska Type Intrusion

PGEs

Refers to magma gneraton and igneous rocks suites produced within lithospheric plate

Intraplate Magmatism

Greatest maniferstaton of intraplate magmatism encompassing volumes of >1000000 cu.km

LIPs (Large Ign Provinces)

Yellowstone is what type of LIP?

SLIP

Volcanic Landforms that rise upward above sea level

Ocean Islands

Volcanically produced peaks below sea level

Seamounts

Broad flat topped areas resulting from large outpourings of lava flowing laterally from source vents

Oceanic Plateaus

Difference of OIB from MORB

More alkalic Enriched in Incompatible elements

MORB: Partial Melts of upper Depleted Mantle OIB:

Partial Melts of a depper, Encriched Mantle-like Source which is non primitvive (Subducting Slab + Mantle Peridotite)

Dominant Rocks in Hawaii

Olvine Tholeiites

Trend of Magma Composition in Hawaii

Early Alkali Basalts Tholeiitic Basalts generating Shield Volcanoes Late Stage Alkali Volcanism (Hawaiiates and Benmoreites)

Alkalic Magma indicates

Low Degrees of Melting as island move away from the hotspot source

Fractionaton Sequence occuring at Ocean Islands

Basalts Hawaiiite Mugearites Benmoreites Trachytes - Saturated Phonolite - Undersaturate Rhyolite -Supersaturated

Largest oceanic Flood Basalt on earth which encompasses a surface area of 2,000,000 sq. km2 and a volume of 60 million cu.km

Ontong-Java Plateau

Age of Ontong Java Plateau

122 Ma (E.Cret)

Basalts of Ontong Java Plateau

Low K-Tholeiitic Basalt

Products of Continental Intraplate magmatsm and volcanism

1) CFBs 2) Continental Rifts 3) Bimodal Volcanism 4) Layered Basic and Ultrabasic Intrusions 5) Utlrabasic suites (Komatiites and Kimberlites) 6) Unusual Array of Alkaline Rocks and Anorogenic Granites

Three largest Bsalt Events which all corresponds to Largest extinction event on Earth

1) Permo-Triassic Siberian Traps 2) Triassic-E.Jurassic CAMP Central Atlantic Magmatic Province 3) Cret-Tertiary Deccan Traps

What does SLIP stands for?

Silicic Large Igneous Provinces

CFB which formed during the break up of Pangaea which produced rift basins and flood basalt in N and S America, Europe and Africa

Central Atlantic Magmatic Province

Rock composition of CAMPS

Tholeiitic (Low TiO2) and Andesitic

Size of Camp

7 Million Sq.Km

Siberian Flood Basalts is mostly

Tholeiitic w/ minor trachyandesites, nephelinites, picrites, volcanic agglomerates an tuffs

Area of Siberian Traps

3.9 Million sq. Km

Flood Basalt in Western India

Deccan Traps

Area of Deccan Traps

1 Million Sq, km

Basalts of Deccan Traps

Tholeiitic w/ minor Alkalic Basalts orignated by fractional crystallization of shallow magma chambers

Continental Rifts Rocks

?Alkalic Basalt ?Alkaline Rocks ?Silicic Rocks

Known Continental Rifts

?East African Rift Basin - Alk. Basalt + Phonolite Trachyte and Carbonatite ?Lake Baikal - Russia ?Basin and Range - USA ?Rio Grande Rift System - USA

Widespread occurrence of Basalt and Rhylolite without Andesite

Bimodal Volcanism

Source of Layered Mafic Intrusions

Differentiation of Eclogite-Peridotite Parent Magmas resulting in mineral segregation within the pluton

Largest LMIs

Stillwater in Montana, USA Bushveld in S.Africa Skaergaard in Green Land

Oldest Known LMI

Stillwater Complex Montana

Age of Stillwater Complex

2.7 Ga NeoArchean

What are the zones of Stillwater complex?

1) Upper Banded Zone - PGEs, Cu, Ni 2) Ultramafic Zone - Cu, Cr, Ni-Sulfides 3) Basal Zone - Cu, Cr, Ni-Suflides

Largest LMI in the world

Bushveld Complx

Age of Bushdveld Complx

2.06 Ga Paleoproterozoic

Layers of Bushveld Complex that contains deposits

1) Granite Capping - Sn, F, Mo 2) Critical Zone - PGE 3) Basal Zone Upper Chromite Horizon - Chromium

Host of Largest PGE Deposit

Merensky Reef

Host of Chromite

UG2 Reef7

What type of intrusion is the Bushveld Complex?

Laccolith saucer type

The youngest Great Pge enriched intrusions

Skaergaard Intrusion, Greenland

Age of Skaergaard

55 Ma (Late Paleocene)

Ultrabasic Volcanic Rocks found exclusively in Archean Greenstone belts characterized by high Mg content (>18%), olivine rich and depleted in Titanium and LREE

Komatiites

Metamorhosed assemblages of green-colored rocks containing layers of Ultrabasic and basic rocks overlain by silicic rocks and sediments

Greenstone Belts

Where and when was komatiites flow first recognized?

1969, Barberton S.Africa

Consist of Needle-like, acicular olivine, Pyx, and chromite phenocrysts in glass groundmass

Spinifex textute

Why is there no Phanerozoic Komatiite?

Due to lower upper Mantle temperature which precludes the extensive mantle melting required to produce komatitic melts

Temperatures at which komatiites form

1575-1800 deg cel

The only known Phanerozoic Kimatiitie

Gorgona Is. Colombia (88 Ma)

Example of Greenstone Belts thath contain Komatiitie

Yilgarn Craton (2.7 Ga) Barberton (3.5 Ga) Canadian Shield (2.7 Ga)

Brecciated, Mg-rich Ultrabasic Rocks that rapidly rise to Earth via cylindrica Diatremes from deep within the mantle

Kimberlites

Temperatures at which kimberlite originates

1200-1400 deg cel (>150km)

What forms from Kimberlite eruptions?

Diatreme Maar

Major Mineral in Kimberlite?

Olivine

Aside from Diamond what other high pressure minerals exist in Kimberlites?

Pyrope Garnet Jadeite Pyroxene

SiO2 Undersaturated Hypabyssal Rocks

1) Carbonatite 2) Lampropyres 3) Lamproites

Shallow/Hypabyssal intrusive to volcanic rocks containining >20% CO3 minerals such as Natrolite, trona, Sodic calcite, Magnesite, and Ankerite

Cabronatite

Magnesium rich volatile rich porphyriticl rocks containing mafic phenocrysts susch as Biotite, Phologopite, Amphibole, Cpx and Melilite Usually associated with kimberlites and continental rift zones

Lamprophyres

K-rich, peralkaline rocks containing leucite, sanidine, phlogopite, richterite, diopside and livine and are enriched in barium, lanthanum, zirconium but are relatively poor in CO2 and occurs in areas of thickened lithosphere

Lamproites

Silicic plutonic rocks unrealted with convergent margin tectonism and occurs in stable cratons and other passive areas.

Anorogenic Granites (A-types)

what is the distinctive age of A-type granites?

Mid Proterozoic

Distinctive texture of Atype granites which refers to Na-Plag overgrowths on preexisting orthoclase crystals (Unlike Perthitic which is formed due to exsolution) Rims of Oligoclase around alkali feldspar megacrysts

Rapakivi Texture