广西云开地区新华铅锌(银)矿床白云母Ar-Ar年代学及其成矿动力学背景

新华铅锌(银)矿床位于钦杭成矿带南端云开地区的六万大山隆起区,是以铅锌为主的含银热液脉型多金属矿床。矿体赋存在含堇青石黑云母花岗岩中,主要呈脉状和透镜状产出。文章利用激光阶段加热技术对与矿化密切共生的白云母进行Ar-Ar年龄测定。结果表明,新华铅锌(银)多金属矿床的~(40)Ar/~(39)Ar坪年龄为(165.3±1.6)Ma(MSWD=0.38),反等时线年龄为(165.2±1.6)Ma(MSWD=0.42),等时线年龄和坪年龄一致,代表了白云母的冷却年龄和矿床的形成年龄,表明该矿床的形成与云开地区燕山早期的岩浆活动有关,这与区域成矿事件相吻合。结合前人对华南地区地球动力学背景的研究成果,初步认为新华铅锌(银)矿床形成于中-晚侏罗世碰撞板块边缘再次活化,岩石圈伸展的构造背景。

Ar-Ar geochronology of muscovite and metallogenic geodynamics of the Xinhua Pb-Zn(Ag) deposit in Yunkai area, Guangxi

The Xinhua Pb-Zn-(Ag) deposit,located in the Liuwandashan granite uplift zone of western Yunkai area which constitutes a part of the southern section of the Qinzhou Bay-Hangzhou Bay (QBHB) metallagenic belt in south China, is a hydrothermal vein type polymetallic deposit. Orebodies exist in the fault zone of the cordierite biotite granite, in the veinlike and lenticular forms. This paper presents precise ⁴⁰Ar/³⁹Ar ages of muscovite related to the mineralization by laser incremental ⁴⁰Ar/³⁹Ar analysis. Muscovite yielded a well-defined ⁴⁰Ar/³⁹Ar plateau age of (165.3±1.6) Ma (MSWD=0.38) and inverse age of (165.2±1.6) Ma (MSWD=0.42). These ages can represent the formation age of the deposit and suggest that the Xinhua deposit is related to the magmatic activities of Yanshanian period, which is in conformity with things of the regional metallogenic events. Combined with the previous studies of the geodynamic settings of South China, the authors consider that the Xinhua deposit was most likely formed in a setting of lithospheric extension because of plate boundary reactivation in the mid-late Jurassic period.