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Joint Meeting Pacific Section, AAPG & Cordilleran Section GSA April 29–May 1, 2005, San José, California

The Relative History of Fluid Flow and Mineralization Along the Keno Fault, East Central Nevada

John G. Solum1, K. Jill Pachell2, and J. P. Evans3
1 Department of Geological Sciences, University of Michigan, 2534 C.C. Little Building, Ann Arbor, MI 48109-1063, [email protected]
2 ExxonMobil Exploration Co, 233 Benmar, Houston, TX 77060
3 Department of Geology, Utah State Univ, Logan, UT UT 84322-450

Syntectonic veins deposited along the moderate-displacement Keno fault in east central Nevada record the history of fluid flow along that fault, as well as the late stages of mineralization in a Carlin-type gold deposit. The concentration of hydrocarbon inclusions decreased as mineralization occurred indicating that the oxidation state of the system increased with time. Sulfide mineralization was followed by sulfate mineralization, which was followed by oxide mineralization, which, along with the confocal laser scanning microscopy observations of the distribution of hydrocarbons, also indicates that the fluid regime became more oxidizing with time. Small-scale d18O and d13C analyses of the syntectonic calcite veins show that the veins formed due to the mixing of fluids from three distinct reservoirs: a mineralizing fluid that migrated along the Keno Fault, a reservoir of formation water contained within the deposit, and minor Tertiary meteoric water.

Posted with permission of The Geological Society of America; abstract also online ( © Copyright 2005 The Geological Society of America (GSA).