Comparison of decrepitation, microthermometric and compositional characteristics of fluid inclusions in barren and auriferous mesothermal quartz veins of the Cowra Creek Gold District, New South Wales, Australia

Abstract

Fluid inclusions in quartz from barren and Au-sulfide-bearing veins from the Cowra Creek Gold District, New South Wales, Australia, have been characterized based on their decrepitation behavior and gas geochemistry. Inclusions in Au-sulfide veins, and some regional sulfide-bearing veins, show distinctly higher CO 2 CH 4 ratios compared to barren quartz-only and quartz-sulfid veins from the deposit environment. Additionally, the occurrence of low-temperature peaks in acoustic decrepigrams from Au-sulfide veins that had previously been attributed to the presence of CO 2-bearing fluid inclusions has been confirmed using optical techniques. This characteristic peak is absent from quartz-sulfide and quartz-only veins. These results suggest that the gas content of fluid inclusions can distinguish Au-bearing from barren quartz veins, and that the acoustic decrepitation technique may provide a rapid and simple means of identifying different generations of quartz, and potentially productive veins in mesothermal environments.