New precise age constraints of the Hatu gold belt, west Junggar, NW China: Implications for a 300 Ma magmatic hydrothermal event in post-collisional setting

Abstract

A 300 Ma magmatic hydrothermal ore-forming process is identified in the Hatu gold belt in west Junggar, northwest China, based on precise age constraint by secondary ion mass spectroscopy U-Pb dating of hydrothermal zircon and Ar-Ar dating of muscovite. The gold deposits in the Hatu belt (Hatu, Qi-V, Huilvshan, etc.) are similar in geology, with NE- and NW-trending orebodies composed of gold-bearing quartz veins and auriferous altered tuffaceous wall-rocks. Hydrothermal zircon grains separated from gold-bearing quartz veins in the Qi-V gold deposit provide a concordia age of 299.6 Ma and a nearly identical weighted mean 206Pb/238U age of 300 ± 2 Ma. Muscovite samples also from the gold-bearing quartz veins yield 40Ar/39Ar plateau ages of 299.6 ± 1.7 Ma, 299.9 ± 1.8 Ma, and 300.6 ± 1.9 Ma. By comprehensive compilation of geological and geochemical characteristics, tectonic evolution, and geochronology of the gold deposits in the Hatu gold belt, our new precise age data confirm that the gold deposits in the Hatu belt formed simultaneously at ca. 300 Ma, and likely formed during a post-collisional extensional setting by magmatic hydrothermal fluid from cooling magmatic sources.