Diversification 2
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Transcript of Diversification 2
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Diversification 2
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Updates:Lab progress?
Topics:Evolving melt compositions:Magma mixingAssimilation
Today
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Magmatic Differentiation
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Stages in ascentEruption(Fragmentation)VesiculationRenewed ascent StoragemixingassimilationcrystallizationBuoyant ascentPartial melting
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Processes during storage in magma chambers
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Magma Mixing
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End-membersMagma Mixing80%
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Mixing vs fractionation
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Mixing vs mingling
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Basalt pillows accumulating at the bottom of a in granitic magma chamber, Vinalhaven Island, MaineComingled basalt-Rhyolite Mt. McLoughlin, OregonFigure 11-8 From Winter (2001) An Introduction to Igneous and Metamorphic Petrology. Prentice Hall
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ABMagma Mixing/Mingling
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Assimilation
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Assimilation-diffusionhttp://iramis.cea.fr/Images/astImg/308_2.jpg
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Assimilation-xenoliths
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Zone meltingCrystallizeMelt
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Detecting and assessing assimilationFigure 9-13. After Wilson (1989). Igneous Petrogenesis. Unwin Hyman/Kluwer.
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Combinations
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Compositional effects of magma chamber processes
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Renewed ascentEruption(Fragmentation)VesiculationRenewed ascent StoragemixingassimilationcrystallizationBuoyant ascentPartial meltingCommon evidence for mixing:Eruptions (renewed ascent) driven by new magma entering magma chamber
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At or near surfaceEruption(Fragmentation)VesiculationRenewed ascent StoragemixingassimilationcrystallizationBuoyant ascentPartial meltingVesicles show gasses unmix: volatile phases escape from meltDoes not affect major or (most) trace elements
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Possible OrigincrustmantlePartial melting in mantle yields basaltic magmaPartial melting of crust -> rhyolitic magmaMixing in magma chambers generates andesite and daciteEruptions are triggered by mixing events.Storage -> crystal fractionation: basaltic andesite
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