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

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6420414

Richards, J P; Spooner, E T.C.

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-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
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152003* -- Geothermal Data & Theory-- Rock-Water-Gas Interactions
58 GEOSCIENCES
580300 -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
ALKALINE EARTH METAL COMPOUNDS
BASALT
BRINES
CALCITE
CALCIUM CARBONATES
CALCIUM COMPOUNDS
CANADA
CARBON COMPOUNDS
CARBON ISOTOPES
CARBONATE MINERALS
CARBONATES
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMISTRY
COPPER COMPOUNDS
COPPER ORES
COPPER SULFIDES
ENERGY SYSTEMS
FLUIDS
GEOCHEMISTRY
GEOLOGIC FISSURES
GEOLOGIC STRUCTURES
GEOTHERMAL FLUIDS
GEOTHERMAL SYSTEMS
GROUND WATER
HEMATITE
HYDROGEN COMPOUNDS
HYDROTHERMAL SYNTHESIS
HYDROTHERMAL SYSTEMS
IGNEOUS ROCKS
INCLUSIONS
IRON COMPOUNDS
IRON ORES
IRON OXIDES
ISOTOPE RATIO
ISOTOPES
MINERALIZATION
MINERALOGY
MINERALS
NORTH AMERICA
ONTARIO
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PARAGENESIS
PETROGENESIS
QUANTITATIVE CHEMICAL ANALYSIS
QUARTZ
ROCK-FLUID INTERACTIONS
ROCKS
SILICON COMPOUNDS
SILICON OXIDES
SILVER ORES
SULFIDES
SULFUR COMPOUNDS
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
VOLCANIC ROCKS
WATER