东天山马头滩金矿的成矿时代及其地质意义

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

马头滩金矿区位于秋格明塔什—黄山韧性剪切带西段南缘,矿床成因研究表明,马头滩金矿的形成受该韧性剪切带的控制。为探讨马头滩金矿的成矿时代及其地质意义,开展了石英流体包裹体成分及Rb-Sr、白云母Ar-Ar和硫化物S同位素分析。石英的Rb-Sr同位素等时线年龄为258.8±6.8Ma,限定了该矿床的形成时代,40Ar-39Ar坪年龄为256.0±1.0Ma,与成矿作用及秋格明塔什韧性剪切带西段右行走滑剪切变形作用在误差范围内一致,说明成矿作用与走滑剪切作用密切相关。S同位素及石英包裹体气液相成分特征表明,成矿流体具有幔源特征,并有壳源物质参与,而由右行走滑剪切及随后的抬升作用导致的压力和温度的降低应是东天山地区剪切带型金矿床形成的动力学背景。

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 chemi-cal 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, sug-gesting 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 addi-tion of crust materials. The decrease of pressure and temperature caused by the dextral strike-slip and subsequent uplift action consti-tuted the main dynamics setting for the formation of shear zone type gold deposits in East Tianshan area.