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Integrating isotopic and geochemical tracers, petrology and geochronology into EarthScope research

Integrating isotopic and geochemical tracers, petrology and geochronology into EarthScope research. Examples from the Wyoming Province Carol Frost Kevin Chamberlain Ron Frost. Present-day crustal structure. Karlstrom et al., 2005 Synthesis of CD-ROM expt. Challenge for EarthScope.

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Integrating isotopic and geochemical tracers, petrology and geochronology into EarthScope research

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  1. Integrating isotopic and geochemical tracers, petrology and geochronology into EarthScope research Examples from the Wyoming Province Carol Frost Kevin Chamberlain Ron Frost

  2. Present-day crustal structure Karlstrom et al., 2005 Synthesis of CD-ROM expt.

  3. Challenge for EarthScope • Identify processes that over Earth history produce observed crustal structure • Tools include geology, petrology, geochemistry, isotope tracers, geochronology • EarthScope’s strength: Integration of all information

  4. Example of the Wyoming Province • >3.5 Ga history • 15% Archean exposure

  5. Beartooth-Bighorn Magmatic Domain 2.85 Ga Bighorn batholith intrudes older gneisses

  6. Beartooth-Bighorn Magmatic Domain 2952 ± 4 Ma 3.00 ± 0.02 Ga Core: 3.25 ± 0.01 Ga 50mm 200mm

  7. Beartooth-Bighorn Magmatic Domain

  8. Beartooth-Bighorn Magmatic Domain

  9. Beartooth-Bighorn Magmatic Domain Petrology, geochemistry, isotopes, geochron. predict: anhydrous mafic residue in lower crust overlain by older felsic crust Geophysical model suggests: faster lower crust overlain by slower upper crust

  10. ~2.67 Ga active margin tectonics

  11. MHSB ~2.67 Ga large-scale structures could be imaged geophysically

  12. 2.63 Ga active margin tectonics Accretion, magmatism & deformation: Tin Cup Tin Cup shear zone, ~5 km wide Meredith, 2005

  13. 2.63 Ga active margin tectonics

  14. 2.63 Ga accretion of terranes, magmatism Area appears not to be underlain by fast lower crust Zircon dates from lower crustal xenoliths cluster at ~2.62-2.65 Ga (Farmer et al. 2005) Fast crust never there? Or destroyed?

  15. Proterozoic events • 2.0 Ga rifting (Cox et al., 2000) • 1.86-1.74 Ga collision along • Great Falls (Mueller et al., 2005; 2002) • Cheyenne belt (Karlstrom and Houston, 1984; Chamberlain, 1998) • 1.47 Ga rifting, Belt basin (Sears et al., 1998) • 1.43 Ga A-type magmatism

  16. 1.43 Ga A-type magmatism, SE WY

  17. 1.43 Ga A-type magmatism

  18. Petrology, isotopes:A-type granitesrequire tholeiitic sourcesand leave mafic residuesGeophysically, a maficunderplate may be imaged

  19. 1.43 Ga A-type magmatism • Frost et al. (Geology, 2001) calculated 15% of SW US crust should be A-type underplate • Deep probe x-section 7.xx layer CD-ROM working group, 2002 Karlstrom et al., 2002

  20. Phanerozoic events • Laramide orogeny (Erslev, 2005) • Tertiary magmatism (Absaroka (Feeley, 2003), Black Hills (Duke, 2005), Rattlesnake Hills (Hoch & Frost, 1993) • Basin & Range extension • Yellowstone hotspot (Dueker &Yuan, 2005; Frost & Frost, 1997)

  21. Geophysical + geologic studies have been fruitful… ..and we have learned much from COCORP to Deep Probe. We are poised to develop integrated experiments that will allow us to relate crustal structure to the processes of lithospheric evolution. . Gorman et al., 2002

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