The genesis of Xindian gold deposit, Liaodong Peninsula, NE China: Constraints from zircon U–Pb ages, S–Pb isotopes, and pyrite trace element chemistry

Abstract

The Xindian deposit is a medium tonnage (>5 tonnes of Au) quartz vein‐type gold deposit located on the south‐central part of the Liaodong Peninsula, China. A total of 37 auriferous quartz veins are hosted within the Paleoproterozoic metamorphic rocks of the Gaixian Formation and Late Triassic porphyritic biotite granite. Mineral paragenesis indicates that gold mineralization took place in three stages: early milky quartz‐pyrite stage, main gray quartz‐polymetallic sulfide and gold stage, and late quartz‐calcite‐pyrite stage. Silicification and pyritization are spatially and temporally associated with the main mineralization stage. Zircon U–Pb dating from dikes that predate and postdate the mineralization constrain the timing of mineralization to the Early Cretaceous, between 127.2 and 120.9 Ma. High‐precision in‐situ S isotope analyses yielded δ34S values for pyrite, sphalerite and galena of 10.1–11.0‰, 10.3–10.5‰, and 8.6–8.8‰, respectively, indicating that S was derived from the multiple sources. In‐situ Pb isotope analyses resulted in 208Pb/204Pb, 207Pb/204Pb, and 206Pb/204Pb ratios of 38.207–38.634, 15.598–15.668, and 18.027–18.143, respectively, for pyrite and galena, suggesting Pb derivation from a mixture of Gaixian Formation metamorphic rocks and other potential sources. In‐situ LA‐ICP‐MS trace element mapping and spot analyses show that the inner core of the pyrite (Py‐ic) formed early and is generally enriched in Au, As, Co, Ni, Bi, and Te, the outer core of the pyrite (Py‐oc) contains less Co, Ni, As, and Au, but more Cu, Pb, and Zn, whereas the rim of the pyrite (Py‐r) is enriched in Ag, Sn, Sb, Cu, Pb, and Zn. Trace element signatures of pyrite reveal that the mineralizing fluid was initially of magmatic‐hydrothermal origin, and subsequently modified by intensive interaction with the wall rock (Gaixian Formation). Our results consistently demonstrate that the Xindian gold deposit is resulted from fluid–rock interaction between the Early Cretaceous magmatic‐hydrothermal fluids and Gaixian Formation metamorphic wall rocks that enriched the metal budget of the mineralizing fluid. Then the addition of meteoric water significantly changed the physical and chemical conditions of the mineralizing fluid, triggering gold precipitation in the Xindian deposit. The results of our study expand the Early Cretaceous gold metallogenic models in the Liaodong Peninsula, highlighting the importance of the Gaixian Formation for regional gold mineralization.