In-situ S–Pb isotopic and trace elemental compositions of sulfides from the Habo Au polymetallic deposit: Evidences for vein-type Au mineralization in the Ailaoshan Au belt

Abstract

The Habo Au polymetallic deposit is located in the south of the Ailaoshan-Red River tectonic zone. Mineralization is controlled by a strike-slip fault, which was intruded by aplite. Ore minerals are dominated by pyrite and arsenopyrite. Gold is invisibly and ionically bound in pyrite and arsenopyrite. Three hydrothermal alteration-mineralization stages can be identified: quartz-pyrite (py1) ± arsenopyrite vein associated with sericite alteration (I), quartz-pyrite (py2)-polysulfide (II) and quartz-calcite (III). The aplite yielded zircon U − Pb ages of ca. 35.4 Ma while the sericite in pyritized siltstone yielded an Ar-Ar age of ca. 37.5 Ma, constraining the mineralizing age. In situ S–Pb isotopic compositions for sulfides were measured by fs-LA-MC-ICP-MS. Sulfides from the deposit show uniform δ34S values ranging from –5.1‰ to + 2.5‰, a typical characteristic of magmatic-derived S. Pb isotopic compositions of galena are similar to those of the granite in the Habo granite complex, suggesting that the metal is probably sourced from the Habo granite complex. In-situ LA-ICP-MS spot analysis indicates that py1 has high Ni, Co, As and Se concentrations while py2 contains higher concentrations of Au, As, Cu, Pb and Zn. These characters reveal that the ore-forming fluids are As-rich and largely unsaturated with respect to Au. Based on the ore deposit geology, dating and isotopic data, the Habo Au polymetallic deposit mineralization is similar to typical intrusion-related vein-type deposit, formed by fluids originated from magma differentiations of the Habo granite complex.