Geochemical environment of mineralization and alteration in the southern Ohio vein, Creede, Colorado

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

OSTI ID:6653170

Gorman, J

Detailed mineralogical, paragenetic, and geochemical studies in the southern Ohio vein at Creede, Colorado, a Tertiary volcanic hosted Pb-Zn-Ag epithermal deposit, indicate that two hypogene vein fluids with distinct redox characteristics alternately precipitated oxidized and reduced assemblages. Oxidized assemblages are characterized by barite and hematite, whereas the reduced fluids appear responsible for the base and precious metal, as well as gangue deposition. The oxidizing fluid was generated either through shallow level boiling or volatile exsolution (CO/sub 2/, H/sub 2/S) of an initially reduced primary hydrothermal fluid or through mixing with an oxidized groundwater. Hypogene events in the wallrock, contemporaneous with vein mineralization, have the following paragenesis: 1) pervasive bleaching of the wallrock via pyritization of groundmass hematite with introduction of reduced hydrothermal vein fluids, 2) argillization (illite with 3-15 +/- 2% interlayered smectite) of the wallrock and disseminated sulfide mineralization, and 3) vein related silicification overprinting earlier events. These reactions result from the introduction of low pH (approx. 5.0), sulfur poor (10/sup -3/ - 10/sup -3.5/ m), reduced (H/sub 2/S) hydrothermal fluids into the wallrock. Mineralization occurred over a decreasing temperature regime (approx. 250 to 180/sup 0/C) possibly coupled with a pH increase related to argillization. The nature and distribution of wallrock alteration is controlled by permeability, fluid composition, and temperature.

• Research Organization: Univ. of Michigan, Ann Arbor (USA)
• OSTI ID: 6653170
• 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

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ALKALINE EARTH METAL COMPOUNDS
BARITE
BARIUM COMPOUNDS
BARIUM SULFATES
CENOZOIC ERA
CHALCOGENIDES
CHEMISTRY
COLORADO
FEDERAL REGION VIII
FLUIDS
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC HISTORY
GEOTHERMAL FLUIDS
HEMATITE
HYDROTHERMAL ALTERATION
IGNEOUS ROCKS
IRON COMPOUNDS
IRON ORES
IRON OXIDES
LEAD ORES
MINERALIZATION
MINERALOGY
MINERALS
NORTH AMERICA
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PARAGENESIS
ROCK-FLUID INTERACTIONS
ROCKS
SILVER ORES
SULFATE MINERALS
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SULFUR COMPOUNDS
TERTIARY PERIOD
TRANSITION ELEMENT COMPOUNDS
USA
VOLCANIC ROCKS
ZINC ORES