Deciphering the genetic relationship between W and Au in a W-Au co-mineralized system: Trace elements of pyrite and sulfur isotopes of sulfides from the Yangwuchang W-Au deposit, North Qinling, China

Abstract

The co-mineralization of W and Au in some deposits has long been noted, yet remains debated. The Yangwuchang W-Au deposit provides an excellent opportunity for examining the genetic relationship between the mineralization of these two elements. In this paper, we present new trace elemental data for pyrite and sulfur isotopic compositions for sulfide minerals to better understand the co-mineralization of W and Au. Type 1 pyrite (Py1) is mainly hosted in the W-bearing veins and has low concentrations of Au (0.01–0.04 ppm), Ag (0.06–437 ppm), and Te (1.77–234 ppm). In contrast, type 2 Pyrite (Py2) in the auriferous veins is relatively enriched in Au (0.06–209 ppm), Ag (0.44–58610 ppm), Te (1.88–42337 ppm), and other trace elements. The concentration of Au has a positive relationship with Te but not with As, suggesting Te melt plays a significant role in scavenging Au from ore-forming fluids during mineralization. The narrow range of δ34S value (-3.17 to 3.69 ‰), combined with high Te contents and Co/Ni ratios of pyrite, indicates that the ore-forming metals may have been derived from a W-Au-rich magma. The slight negative values of δ34S in Py1 infer the localized pressure fluctuations during W mineralization. We concluded the W and Au could be both derived from one single magma system. The deep part of Au-bearing veins has great exploration potential for W mineralization.