Sub-solidus evolution
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Geology Study Notes: Sub-solidus Evolution and Mineral Transformations, Slides of Geochemistry
An overview of sub-solidus evolution, mineral transformations, and secondary mineral formation. Topics include polymorphs, exsolutions, phase diagrams, feldspar solvus, perthites, and secondary mineral reactions. The document also covers hydrothermal alteration and the formation of various minerals such as stishovite, coesite, and quartz.
Typology: Slides
2012/2013
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Sub-solidus evolution
- Mineral transformations• Secondary minerals• Fluids expulsion and movement– Pegmatite/aplite veins– Mineralized veins• Hydrothermal alteration– Episyenites, endoskarns, greisens– Exoskarns
Phasediagram forSiO^2
Stishovite Coesite^ - quartz - quartz
Liquid CristobaliteTridymite 600 1000 1400 1800 2200 2600 10 8 6 Pressure (GPa)^42
o^ Temperature C
Feldsparsolvus
Opx-Cpx exsolution
Secondary minerals• « Autometamorphism »
Secondary minerals• Px => Amp => Bt • Px, Amp, Bt^ => chlorite (
phyllosilicate
-^ K-feldspar, feldspathoids
=> sericite
( fine white mica
-^ Ca-plagioclase
=> saussurite (
epidote )
-^ Olivine
=> serpentine (
complex phyllosilicate
), iddingsite (
a mixture of various Fe-Mg silicates