Preservation and exhumation history of the Harizha-Halongxiuma mining area in the East Kunlun Range, Northeastern Tibetan Plateau, China

Abstract

The extent to which ore bodies are preserved in orogenic belts remains a poorly understood area of ore deposit research. Using zircon and apatite fission track analysis together with apatite (U-Th)/He dating we constrained the erosion history of the ore bodies in the Harizha–Halongxiuma mining area of the East Kunlun Range, Northern Tibetan Plateau, China. Apatite fission-track ages range from 114±8 to 87±6Ma, with mean track lengths varying from 11.4±1.9 to 12.9±2.0μm. Zircon fission-track ages vary from 205±14 to 142±7Ma. In addition, apatite (U–Th)/He dating yielded ages of 60–56Ma. The thermal history of Jiapigou was modelled based on the apatite fission-track data, including ages and track lengths, with constraints of zircon fission-track ages and (U-Th)/He ages. The exhumation history of the Harizha–Halongxiuma mining area was reconstructed with these age data, revealing that since the early Mesozoic the area has undergone three cooling stages: (1) rapid cooling from 175±30Ma to 100±10Ma with a cooling rate and inferred exhumation of 2.0±0.8°C/Myr and 4.3±1.7km, respectively; (2) a relatively stable stage from 100±10Ma to 40±10Ma with a cooling rate and inferred exhumation of 0.3±0.1°C/Myr and 0.5±0.2km, respectively; and (3) rapid cooling since 40±10Ma with a cooling rate and inferred exhumation of 1.2±0.6°C/Myr and 1.4±0.4km, respectively. This exhumation history is consistent with the subduction process of Pacific plate and the strike slip movements of Dunmi fault. The total exhumation after main mineralization is calculated to be 7.6±3.2km, suggesting that ore bodies in the Harizha–Halongxiuma mining area remain partially preserved.