Structural characterization of the Katebasu gold deposit, Xinjiang, China: Tectonic correlation with the amalgamation of the western Tianshan

Abstract

The western Tianshan orogen is one of the world’s most important gold provinces. It hosts numerous world-class gold deposits along the southern and northern margins of the Middle Tianshan. Most deposits occur within large-scale fault zones and/or ductile-brittle deformation zones that were formed during the Paleozoic evolution of the Paleo-Asian Ocean, thereby indicating a correlation between orogenic tectonics and the gold mineralization. However, the correlation is often poorly constrained and remains controversially discussed. The Katebasu gold deposit in Xinjiang, China, is located on the northern margin of Middle Tianshan and is hosted by secondary fault zones to the south of the North Nalati Fault. The main period of gold mineralization is suggested to be the Late Carboniferous, which is broadly coeval with the late Paleozoic amalgamation of the western Tianshan. Therefore, the Katebasu gold deposit provides an excellent opportunity to search for possible correlations between structural processes at a deposit scale and orogenic processes at a regional scale to better understand the tectonic controls on large-scale gold mineralization in the western Tianshan. In this paper, we report detailed structural mapping and field investigations on the fault geometries and kinematics of the Katebasu gold deposit that permit inversion of the tectonic stress field. Our structural data, combined with results of previous studies of the regional tectonics, allow us to reconstruct the structural history of the Katebasu gold deposit, to look for possible correlations with the orogenic processes in the western Tianshan and to determine their control on gold mineralization. The first stage of deformation (D1) was top-to-the-north thrusting that was caused by a roughly N–S compression and is represented by ENE–WSW-striking thrust faults. D1 was likely related to the closure of the South Tianshan Ocean and the resulting collision between the Tarim craton and Middle Tianshan–Yili block. The second stage of deformation (D2) was dextral strike-slip motion along the ENE–WSW-striking faults that was caused by the WNW–ESE stress field and that corresponds to Permian dextral wrenching in the Tianshan orogen. Subsequent NE–SW compression led to the third deformation event (D3) that mainly formed NW–SE-striking reverse faults and NNE–SSW-striking dextral faults.