Mineralogical and fluid inclusion characteristics of epithermal-style gold mineralization at the Goldy and Irene showings, Dawson Range, Yukon Territory, Canada

Abstract

Jurassic- to Cretaceous-age gold mineralization at the Goldy and Irene showings in the Dawson Range, Yukon Territory occurs in intrusive igneous bodies and metasedimentary rocks of the Yukon-Tanana terrane. Petrography, fluid inclusion microthermometry, electron microprobe analysis, and SEM-BSE techniques were used to study the characteristics of Au mineralization. At the Goldy showing mineralization consists of: pyrite, arsenopyrite, chalcopyrite, (suspected) dissolved gold in sulfides, sphalerite, galena, +/- tetrahedrite-tennantite, +/- rutile and boulangerite in multiple stages of hydrothermal quartz-carbonate veining. At the Irene showing mineralization consists of: pyrite, arsenopyrite, chalcopyrite, galena, stibnite, electrum, rutile, boulangerite, and a variety of Sb-sulfides and sulfosalts hosted in quartz-carbonate veining. Fluid inclusion microthermometry of secondary inclusions hosted in quartz showed salinity ranges of 0- 6 wt% NaCl eq at Goldy, and homogenization temperatures (Th^L+V→L) of 200-250 °C. At Irene salinity ranges of 5-15 wt% NaCl eq. and Th^L+V→L of 140-230 °C were determined. The results of mineralogical and fluid inclusion studies suggest that the showings can be classified as low- (to intermediate)-sulfidation epithermal style mineralization. The dissimilarity of salinities and Th^L+V→L values, with Irene being a cooler (and possibly deeper) hydrothermal system with higher salinities than Goldy indicates differing distances from a common heat source and more pronounced involvement of meteoric water at Goldy. Two different mineralizing events are proposed: a high T event involving As-Au association, and a lower T event, more consistent with epithermal T conditions involving Sb-Au association that is more pronounced at the Irene showing.