Multistage mineralization of the Liling goldfield (NE Hunan) in the Jiangnan Orogen: Constraints from hydrothermal rutile U–Pb dating and sericite Rb–Sr dating

Abstract

The Liling goldfield located in northeastern (NE) Hunan contains 100 tons of proven gold reserves. The gold mineralization age in Liling has long been controversial due to the lack of datable minerals. In this study, petrographic observations indicate that hydrothermal rutile and sericite were precipitated with auriferous pyrite/arsenopyrite in the ore veins. The electron probe microanalysis (EPMA) results show that the sericite from ores and the sericite from Neoproterozoic slate display distinct compositions (Especially Al, K, and Ti). The high W (1,081–36,456 ppm) and low Zr (21.35–288.7 ppm) contents of the rutile suggests a hydrothermal origin. We reported new laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb ages of ore-stage hydrothermal rutile (415.2 ± 8.3 Ma) for the Tuanshanbei gold deposit, and sericite Rb-Sr ages (417.6 ± 12.9 Ma and 216.9 ± 7.8 Ma) for the Tuanshanbei and Yanlinsi gold deposits in the goldfield. The new data confirm that multistage gold mineralization has occurred in the Liling goldfield, and falls within the generally accepted timing (ca. 430–400 Ma and 250–200 Ma) of gold mineralization in the Jiangnan Orogen. Integration of geological characteristics, tectonic setting, and geochronology of the Liling goldfield suggest two Au mineralization episodes, which occurred in the Late Silurian-Early Devonian intracontinental orogeny and Triassic intracontinental orogeny, respectively.