Fluid inclusion and stable isotope evidence for mixing of magmatically related fluids with ground waters during Keweenawan Cu-Ag fissure-vein mineralization, Mamainse Point, Ontario
Primary chalcocite (Cc) mineralization at the Coppercorp mine occurs with vuggy Qz and minor calcite (Ct) in hydrothermal breccia veins following normal faults which cut Keweenawan plateau basalts and interflow sediments. Cc is the last and predominant sulfide in a paragenetic sequence of Py-Cp-Bn-Cc-Cu/sup 0/. Hematite (Hm) is found in equilibrium with all sulfides except Py. Fluid inclusion studies of vein Qz reveal a simple mixing trend between high temperature, high salinity brines, and lower temperature, more dilute hybrid fluids. The high end-member fluid temperatures strongly suggest a magmatic association, while the low salinity fluids are probably meteoric ground waters. delta/sup 13/C/sub pdb/ and delta/sup 18/O/sub smow/ values for ten Ct samples associated with sulfides average -4.0 per thousands (s=0.7) and 13.3 per thousands (s=2.1) respectively. These results suggest that the Coppercorp high-temperature ore-fluids were in equilibrium with an intrusion similar to the Jogran porphyry at depth, and that mixing with ground waters at higher levels in fissure veins resulted in sulfide precipitation by cooling, dilution and neutralization. Oxidation of this primary fluid at Coopercorp is also reflected by the ubiquitous presence of Hm with sulfide ores; negative delta/sup 34/S ratios from ten samples of Py, Cp or Cc and positive ratios from two rare baryte samples support this interpretation. Two samples of Py from Jogran give ratios typical of porphyry deposits, and may therefore represent the original undisturbed values of the ore-fluid.
- Research Organization:
- Univ. of Toronto, Ontario (Canada)
- OSTI ID:
- 6420414
- 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 Oct 1985
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
58 GEOSCIENCES
COPPER ORES
MINERALIZATION
MINERALOGY
QUANTITATIVE CHEMICAL ANALYSIS
GEOTHERMAL FLUIDS
GEOCHEMISTRY
ONTARIO
HYDROTHERMAL SYSTEMS
BASALT
BRINES
CALCITE
CARBON ISOTOPES
COPPER SULFIDES
GEOLOGIC FISSURES
GROUND WATER
HEMATITE
HYDROTHERMAL SYNTHESIS
INCLUSIONS
ISOTOPE RATIO
OXYGEN ISOTOPES
PARAGENESIS
PETROGENESIS
QUARTZ
ROCK-FLUID INTERACTIONS
SILVER ORES
ALKALINE EARTH METAL COMPOUNDS
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CANADA
CARBON COMPOUNDS
CARBONATE MINERALS
CARBONATES
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMISTRY
COPPER COMPOUNDS
ENERGY SYSTEMS
FLUIDS
GEOLOGIC STRUCTURES
GEOTHERMAL SYSTEMS
HYDROGEN COMPOUNDS
IGNEOUS ROCKS
IRON COMPOUNDS
IRON ORES
IRON OXIDES
ISOTOPES
MINERALS
NORTH AMERICA
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
ROCKS
SILICON COMPOUNDS
SILICON OXIDES
SULFIDES
SULFUR COMPOUNDS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
VOLCANIC ROCKS
WATER
152003* - Geothermal Data & Theory- Rock-Water-Gas Interactions
152001 - Geothermal Data & Theory- Properties of Aqueous Solutions
580300 - Mineralogy
Petrology
& Rock Mechanics- (-1989)
580400 - Geochemistry- (-1989)