Metallogenic age of the Matoutan gold deposit in East Tianshan and its geological significance

The Matoutan gold ore district is located at the south edge of the west section of the Qiugemingtashi-Huangshan ductile shear zone. The study of the genesis of the Matoutan gold deposit shows that its formation was controlled by this ductile shear zone. In order to discuss the ore-forming age of the Matoutan gold deposit and its geological significance, the authors analyzed the chemical and Rb-Sr isotope composition of fluid inclusions in the quartz and measured the Ar-Ar isotope of muscovite and sulfur isotope of sulfide. The fluid inclusions of quartz yielded an Rb-Sr isochron age of 258.8±6.8Ma, which represents the ore-forming age of the Matoutan gold deposit. The muscovite yielded an Ar-Ar plateau age of 256.0±1.0Ma, which is in agreement within error with the metallogenic and the dextral strike-slip shearing activities along the west section of the Qiugemingtashi ductile shear zone, suggesting that the gold mineralization and the strike-slip action were closely related to each other. The characteristics of sulfur isotope and the fluid inclusions composition in the quartz indicate that the ore-forming fluid had the mantle-derived attribute with the addition of crust materials. The decrease of pressure and temperature caused by the dextral strike-slip and subsequent uplift action constituted the main dynamics setting for the formation of shear zone type gold deposits in East Tianshan area.