Abstract

Molybdenite, wolframite, and scheelite were deposited at temperatures between 380 degrees and 200 degrees C from fluids with salinities between 3.7 and 11.1 equivalent wt percent NaCl at pressures below 180 bars. Late-stage carbonates and fluorite were deposited at temperatures between 190 degrees and 150 degrees C. The delta 34 S values of sulfides within the mine have the following ranges and values: molybdenite, 3.0 to 5.7 per mil; pyrite 4.5 to 7.6 per mil; pyrrhotite, 4.8 to 5.1 per mil; chalcopyrite, 4.8 per mil; sphalerite, 3.0 to 5.7 per mil; and galena, 3.9 per mil. An early, pervasive flow of water-rich fluids which took place uniformly throughout the carbonate rocks during metamorphism is suggested for nonmineralized regions. Channeled flow within structurally controlled aquifers and fracture systems during metamorphism (high water-to-rock ratios) is suggested for mineralized regions. Later ore fluids followed these same restricted pathways while depositing ore minerals. The geochemical and isotope data suggest that the overall hydrothermal system was characterized by low water-to-rock ratios, but local areas with channeled fluid flow were characterized by high water-to-rock ratios.--Modified journal abstract.

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