Pressures of skarn formation at Casting Copper NV, USA, based on Raman spectroscopy and elastic modeling of apatite inclusions in garnet
Abstract
Thermobarometry of metasomatic rocks is commonly challenging, owing to the high variance of hydrothermal mineral assemblages, thermodynamic disequilibrium and overprinting by subsequent hydrothermal episodes. Here, we estimate formation pressures of a Cu-Fe-sulfide-bearing andradite-diopside skarn deposit at Casting Copper (Yerington district, NV) using Raman spectroscopy and elastic modeling of apatite inclusions in garnet. Andradite garnet from the Casting Copper skarn contains inclusions of hydroxyl-fluorapatite, calcite, hematite, magnetite, and ilmenite. Raman spectroscopy reveals that the apatite inclusions are predominantly under tension of -23 to -123 MPa at ambient conditions. Elastic modeling of apatite-in-garnet suggest entrapment occurred at 10 to 115 MPa, assuming a trapping temperature of 400 °C, which is consistent with paleodepth estimates of 2-3 km. These results provide independent constraints on the conditions of hydrothermal skarn formation at Casting Copper, and suggest that this approach may be applied to other, less-constrained skarn systems.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.V33G0589S
- Keywords:
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- 1012 Reactions and phase equilibria;
- GEOCHEMISTRY;
- 1043 Fluid and melt inclusion geochemistry;
- GEOCHEMISTRY;
- 3625 Petrography;
- microstructures;
- and textures;
- MINERALOGY AND PETROLOGY;
- 3651 Thermobarometry;
- MINERALOGY AND PETROLOGY