A review of the geological characteristics and geodynamic mechanisms of Late Paleozoic epithermal gold deposits in North Xinjiang, China

Abstract

In this review, we describe the geological characteristics of Late Paleozoic epithermal gold deposits in North Xinjiang, and place these into their metallogenic–tectonic context. These gold deposits can be divided into high-sulfidation and low-sulfidation types, with the latter being predominant. The spatial distribution of epithermal gold deposits in North Xinjiang is controlled by calderas, craters, diatremes and related faults. The volcanic and sub-volcanic host lithologies of the gold deposits are mainly of calc-alkaline affinity and dominated by basalt–andesite–dacite–rhyolite suites, and associated pyroclastic rocks. Alteration assemblages are dominated by adularia–chalcedony–sericite for low-sulfidation gold deposits, and alunite–kaolinite–quartz (chalcedony) for high-sulfidation gold deposits. Homogenization temperatures of fluid inclusions in the high-sulfidation type epithermal deposits range from 200 to 300 °C, and ore-forming fluids were mainly of magmatic-hydrothermal origin (e.g. Jingxi–Yelmand), with some contributions from meteoric water. Homogenization temperatures of fluid inclusions in the low-sulfidation type epithermal deposits range mainly from 120 to 210 °C, and ore-forming fluids were largely derived from meteoric water. The high-sulfidation type and low-sulfidation type epithermal deposits have similar salinities, ranging from 0.2 to 19.2 wt.% NaCl equiv. with a cluster between 0.3 and 13 wt.% NaCl equiv. Based on isotopic age data, the epithermal gold deposits essentially appear to have formed during three broad intervals: 346–300 Ma (with a peak at ~ 340–330 Ma), 290–270 Ma, and 240–226 Ma. Each of these episodes corresponds to a period of syncollision, postcollision and intraplate tectonics during Late Paleozoic, accretionary and collisional evolution of the Siberian, Junggar–Kazakhstan and Tarim plates.