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Contact metamorphism & fluids

Contact metamorphism & fluids. Can fluid composition change during met?. Fluid composition. It can change composition during metamorphism Internally buffered Fluids evolved stay in system Top reaction, when do you leave the reaction line?. What if an open system?

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Contact metamorphism & fluids

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  1. Contact metamorphism & fluids

  2. Can fluid composition change during met?

  3. Fluid composition • It can change composition during metamorphism • Internally buffered • Fluids evolved stay in system • Top reaction, when do you leave the reaction line?

  4. What if an open system? • Infiltrated by external fluids • What is fluid composition here?

  5. Paths of buffered or open system fluidsalso note pressure changes

  6. Calc-silicates • Marbles: pure carbonate • Calc-silicates: carbonate with silicates • Skarn: calc-silicate formed by metasomatism

  7. What are index minerals for calc-silicates?

  8. Intrusion 1/2 Km

  9. Talc Intrusion 1/2 Km

  10. Intrusion Tremolite Talc 1/2 Km

  11. Intrusion Forsterite Tremolite Talc 1/2 Km

  12. Intrusion Periclase+Fo Forsterite Tremolite Talc 1/2 Km

  13. +Pe +Fo +Tr Intrusion Periclase+Fo Forsterite Tremolite Talc 1/2 Km

  14. Index minerals in calc-silicates • Talc • Tremolite • +/- diopside • Forsterite • Periclase • Monticellite

  15. Ubehebe contact aureole • No talc zone, why?

  16. Index minerals for Ubehebe Peak

  17. Tremolite blossoms in silicious dolostone • Fluid along cracks, not pervasive

  18. More evidence for localize fluid flow • Periclase zone

  19. What sequence of index minerals if externally buffered fluid: • XCO2 = 0.5 • XCO2 = 0.05 • XCO2 = 0.9

  20. What sequence of index minerals if low quartz content in protolith? • Which reactions? • Protolith: dolomite, calcite, some quartz • XCO2 < 0.6

  21. In what kind of protolith can you find wollastonite?

  22. Plutons in NE Utah

  23. Alta stock contact aureole ~31 Ma

  24. Alta Contact Aureole at Albion Basin Index Minerals

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