Origins of the Pangkaimen Au Deposit in the Northern Great Xing'an Range, China: Evidence From Geochronological, Geochemical, Fluid Inclusion, and <scp>H–O–S–Pb</scp> Isotope Data

ABSTRACT The gold (Au) metallogenic belt in the northern Great Xing'an Range is characterised by the wide occurrence of the Early Cretaceous orogenic and epithermal Au deposits. Systematic studies of the Pangkaimen Au–Ag deposit could shed new light on the Early Cretaceous Au metallogenesis in this area. The purpose of this study is to determine the ages of mineralisation, reveal the source, and evolution of the ore‐forming fluid system, and discuss the source of the ore‐forming materials of the deposit. The ore‐bearing pyrite Rb–Sr dating yielded an age of 118 ± 2 Ma. The fluid inclusion studies showed that the ore was precipitated from the hydrothermal fluids within a temperature and salinity range of 232°C–345°C and 2.1–8.7 wt.% equivalent, respectively. H–O isotopic compositions indicate the involvement of both magmatic and meteoric water in the hydrothermal system with fluid mixing which are the major mechanisms behind mineral precipitation. The pyrite and sphalerite S (δ 34 S V–CDT values: −0.3‰ to 4.33‰) and Pb ( 206 Pb/ 204 Pb ratios of 18.334–18.372; 207 Pb/ 204 Pb ratios of 15.550–15.566) isotopic compositions suggest that the ore‐forming materials were derived from the basic‐intermediate volcanic rocks of the Lower Cretaceous Longjiang Formation.