82280616 bowen s reaction series

7/28/2019 82280616 Bowen s Reaction Series

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Silicon-

OxygenTetrahedron

(SiO4)

Isolated Tetrahedrons

(Olivine)


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Tetrahedron Arrangement

S ingle-Chain Double-Chain S heet

Pyroxene Amphibole Mica


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Common silicate minerals


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Igneous Rock Textures

Igneous Rock Textures

T extureT exture refers to the size, shape andrefers to the size, shape andarrangement of grains or other constituentsarrangement of grains or other constituentswithin a rock within a rock

Texture of igneous rocks is primarilyTexture of igneous rocks is primarilycontrolled bycontrolled by cooling ratecooling rateE xtrusive igneous rocksE xtrusive igneous rocks cool quickly at or cool quickly at or near E arths surface and are typicallynear E arths surface and are typically f f ineine--

grained grained (most crystals 1 mm)

Coarse-grained igneous rock

Fine-grained igneous rock


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I gneous rocksClassification is based on the rock's textureand mineral constituents

Texture

Size and arrangement of crystalsTypes

Fine-grained fast rate of coolingCoarse-grained slow rate of cooling

Porphyritic (two crystal sizes) two rates of coolingGlassy very fast rate of cooling


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I gneous Rock I dentificationI gneous Rock I dentificationI gneous rock names are based onI gneous rock names are based on texturetexture (grain size) and(grain size) andmineralogicmineralogic compositioncompositionT extural classi f icationT extural classi f ication

P lutonic P lutonic rocksrocks ((gabbrogabbro--dioritediorite--granite) are coarsegranite) are coarse- -grained and cooledgrained and cooledslowly at depthslowly at depth

VolcanicVolcanic rocksrocks (basalt(basalt--andesiteandesite--rhyoliterhyolite) are typically fine) are typically fine- -grained andgrained andcooled rapidly at the E arths surfacecooled rapidly at the E arths surface

Compositional classi f icationCompositional classi f ication M a f ic M a f ic rocksrocks ((gabbrogabbro--basalt) contain abundant dark basalt) contain abundant dark- -coloredcolored

ferromagnesian mineralsferromagnesian minerals I ntermediate I ntermediate rocksrocks (diorite(diorite--andesiteandesite) contain roughly equal amounts of ) contain roughly equal amounts of

dark dark-- and lightand light--colored mineralscolored minerals Felsic Felsic rocksrocks (granite(granite--rhyoliterhyolite) contain abundant light) contain abundant light- -colored mineralscolored minerals


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I gneous Rock ChemistryI gneous Rock ChemistryRock chemistry, particularlyRock chemistry, particularly silica silica (SiO(SiO 22) content, determines) content, determines

mineral content and general color of igneous rocksmineral content and general color of igneous rocks Ultrama f icUltrama f ic //UltrabasicUltrabasic rocks have 63% silica, by weight, and containlightlight--colored minerals that are abundant in silica, aluminum, sodiumcolored minerals that are abundant in silica, aluminum, sodiumand potassiumand potassium------------------ Oversaturated rocksOversaturated rocks

Intrusive/extrusiveIntrusive/extrusive felsicfelsic rocksrocks -- granite/granite/rhyoliterhyolite


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B owens Reaction SeriesB owens Reaction SeriesM

inerals crystallize in a predictable order, over a largeM

inerals crystallize in a predictable order, over a largetemperature rangetemperature rangeE arly f ormed mineral + remaining melt = new mineral E arly f ormed mineral + remaining melt = new mineral

Discontinuous branch Discontinuous branch Ferromagnesian minerals (olivine, pyroxene, amphibole,Ferromagnesian minerals (olivine, pyroxene, amphibole, biotite biotite))

crystallize in sequence with decreasing temperaturecrystallize in sequence with decreasing temperature As one mineral becomes chemically unstable in the remainingAs one mineral becomes chemically unstable in the remaining

magma, another begins to formmagma, another begins to form

Continuous branchContinuous branch Plagioclase feldspar forms with a chemical composition that evolvesPlagioclase feldspar forms with a chemical composition that evolves

(from Ca(from Ca--rich to Narich to Na--rich) with decreasing temperaturerich) with decreasing temperature


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Observations from B owensObservations from B owensLarge variety of igneous rocks is produced byLarge variety of igneous rocks is produced by

diversification of diversification of magma compositionsmagma compositions

M a f ic M a f ic magmasmagmas will crystallize intowill crystallize into basalt basalt or or gabbro gabbro if if earlyearly--formed minerals are not removed from the magmaformed minerals are not removed from the magma

I ntermediate magmas I ntermediate magmas will similarly crystallize intowill similarly crystallize intodioritediorite or or andesiteandesite if minerals are not removedif minerals are not removed

Separation of earlySeparation of early- -formed ferromagnesian mineralsformed ferromagnesian minerals

from a magma body increases the silica content of thefrom a magma body increases the silica content of theremaining magmaremaining magma

M inerals melt in the reverse order of that in which theyM inerals melt in the reverse order of that in which theycrystallize from a magmacrystallize from a magma


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82280616 bowen s reaction series

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