Fluid inclusion and isotopic studies of the galena mine, Coeur d'Alene district, ID
The Ag-Cu-Pb ores of the Galena Mine in the Coeur d'Alene District of Northern Idaho are mesothermal, vein-type ores, localized along steeply dipping fractures in Proterozoic, Belt Supergroup rocks. The veins are primarily filled with siderite with lesser amounts of quartz, tetrahedrite (td), chalcopyrite (cp), galena (gn), pyrite (py), and arseno-pyrite (asp). Siderite and arsenopyrite deposition predates that of main-stage td, cp, gn, py, and quartz. Oxygen isotopic analyses of quartz show values ranging from 9.8 /per thousand/ to 18.0 /per thousand/, averaging 14.5 /per thousand/. The /delta//sup 18/O values of the Revett Quartzite country rock range from 12.2 to 13.8 /per thousands/. Calculated /delta//sup 18/O/sub H/sub 2/O/ at 325/degree/C is approximately 8.5 /per thousand/, suggesting exchange of isotopically light meteoric water with isotopically heavy country rocks. Analyses of carbon and oxygen isotopes in siderite are highly variable. The /delta//sup 13/C values vary from -8.3 to -4.4, as /delta//sup 18/O varies from 11.7 to 19.0 /per thousand/ respectively. These analyses describe a simple curve, concave to the /delta//sup 13/C axis. This trend may result from deposition from a constant carbon and oxygen reservoir of -5.6 /per thousand/ and 9.3 /per thousand/, respectively, with varying temperature. Fluid inclusions from quartz vugs contain constant proportions of liquid H/sub 2/O, liquid CO/sub 2/, and vapor. The inclusions rupture before homogenizing at temperatures around 325/degree/C. Freezing temperatures average -7.5/degree/C, indicating a salinity of /approx/ 11 wt. percent NaCl Equiv. CO/sub 2/ comprises a mole fraction of .05 to .1 of extracted fluids. Analysis of water extracted from the inclusions show /delta/D to vary from -110 to -144 /per thousand/, strongly suggesting a meteoric water origin of the mineralizing fluid.
- Research Organization:
- Indiana Univ., Bloomington (USA)
- OSTI ID:
- 5892647
- Report Number(s):
- CONF-8510489-
- Journal Information:
- Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28-31 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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INCLUSIONS
MINERALIZATION
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HYDROTHERMAL SYSTEMS
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CHEMICAL COMPOSITION
CARBON ISOTOPES
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GEOCHEMISTRY
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