西天山卡特巴阿苏金矿床成矿年代学及其地质意义-来自绢云母~(40)Ar-~(39)Ar同位素年龄证据

新疆卡特巴阿苏金矿床是近年来在西天山地区新发现的一个大型金矿床。该矿床大地构造位置处于塔里木板块和哈萨克斯坦-准噶尔板块结合部位的那拉提构造-岩浆岩带,其金矿体主要赋存于蚀变二长花岗岩内。为了确定金矿化的形成时代,对该矿床主成矿阶段与金矿化密切相关的蚀变绢云母开展了40Ar-39Ar同位素定年测试。绢云母40Ar-39Ar坪年龄为(268.56±1.8)Ma,正等时线年龄为(268.38±2.2)Ma,反等时线年龄为(268.52±2.2 Ma),三者在误差范围内一致,测试结果可信,可代表卡特巴阿苏金矿化的形成年龄,这也是首次对该矿床成矿年龄的精确限定。对比中亚造山带典型金矿床,卡特巴阿苏金矿床是西天山二叠纪后碰撞构造环境下岩浆流体活动的产物,矿床成因属与中温岩浆热液有关的构造蚀变岩型矿床。

Geochronology of the Katabaasu gold deposit in West Tian Shan and its geological significance: Evidence from 40 Ar-39Ar isotopic ages of sericite

The Katabaasu gold deposit is a newly discovered large deposit in West Tian Shan. Tectonically, it lies at the Nalati tectonic magmatic belt in the convergent area between the Tarim and Kazakhstan-Junggar plates. The gold ore bodies are mainly hosted in the altered monzogranite. In order to define the gold mineralization age, the altered sericites closely related with the mineralization are analyzed by using the 40Ar-39Ar isotopic dating method. The results show that the plateau age is 268.56 ±1.8 Ma and the isochron age is 268.35±2.2 Ma with an inverse isochron age of (268.52 ±2.18) Ma, respectively. These three values are consistent in the error limit and the test data is reliable. Thus, the 40Ar-39Ar ages of the sericite can be regarded as the first reported ore forming time of the Katebaasu gold deposit. Compared with several typical gold deposits in the central Asian orogenic belt(CAOB), the Katabaasu gold deposit was resulted from magma-fluid activity of the Permian in the post-collision tectonic setting of West Tian Shan. The genesis of the gold deposit is the tectonic-altered rock type related to the mesothermal magmatic hydrothermal solution.