Mineral paragenesis and ore fluids at the Turquoise Ridge gold deposit, Nevada

Michiko Shigehiro, University of Nevada, Las Vegas


In this study, mineral assemblages and related fluid inclusions at the Turquoise Ridge Carlin-type gold deposit were examined to answer the following questions: (1) What is the ore-stage mineral paragenesis? (2) At what pressures and temperatures did the deposits form? (3) What are the sources of ore fluids?;Pyrite with gold, jasperoid quartz, stibnite, orpiment, realgar, and calcite were successively deposited at Turquoise Ridge. Microthermometric data and isotopic ratios of inclusion fluids in ore-related minerals indicate entrapment of multiple generations of fluids in pre-ore, ore-, and late-ore stage minerals. Primary fluid inclusions in an ore-stage jasperoid quartz crystal have salinities of 12.6 to 19 wt.% NaCl equivalent, and most inclusions homogenized between 130° and 193°C Isotopic signatures of inclusion fluids in ore-state jasperoid quartz, deltaD = -33‰ and delta 18O = +7.1 to +12.2‰ and deltaD = -46‰ and delta 18O = +5.4 to +10.5‰, are consistent with a magmatic or metamorphic source, or both, while inclusion fluids in late-ore stage calcite yielded delta 18O = 10 to 14.5‰ and deltaD = -110‰, indicating trapping of an evolved meteoric fluid.