云南个旧卡房矽卡岩型铜(锡)矿Re-Os年龄及其地质意义

Re-Os dating of molybdenite from the Kafang skarn copper(tin)deposit in the Gejiu tin polymetallic ore district and its geological significance

云南个旧超大型锡多金属矿田是一个驰名中外的超大型锡多金属矿田,卡房是该矿田的一个重要的铜(锡)矿床。本文利用 Re-Os 同位素定年方法对卡房矽卡岩型矿体中5件辉钼矿样品进行了成矿时代测定,获得辉钼矿 Re-Os 同位素模式年龄为82.95±1.16Ma～83.54±1.31Ma,等时线年龄为83.4±2.1 Ma。该年龄和老卡岩体的 LA-ICP-MS 锆石 U-Pb 年龄85±0.85Ma 相吻合,表明成岩和成矿关系密切。辉钼矿 Re 含量显示成矿过程有地壳和地幔的共同参与。该 Re-Os 定年结果显示个旧卡房矽卡岩型铜(锡)矿床与云南都龙锡锌矿床、云南白牛厂银多金属矿床、广西大厂锡多金属矿床以及广西王社铜钨矿床的成矿年龄接近,表明这些矿床的形成受控于相同的地球动力学背景,同为华南中生代晚期大规模成矿作用的产物。

The Gejiu tin polymetallic ore district is a famous tin polymetallic ore producing area in Yunnan Province. The Kafang skarn copper （tin） deposit is one of important mineral deposits of the Gejiu region. Re-Os dating of five molybdenite separated from the Kafang skarn ore bodies gives an isochron age of 83.4 ±2. 1Ma and model age ranges from 82. 95 ± 1.16 to 83.54 ± 1.31Ma. This age is in good agreement with Laoka granite zircon LA-ICP-MS U-Pb age（ 85 ± 0. 85Ma）. These ages suggest that the mineralization in the Kafang skarn deposit was genetically assoicatted to the Laoka granite. The Re contents of molybdenite indicate that ore-forming materials are derived from mantle and crust. Based on the geochronological data of Dulong Sn-Zn deposit, Bainiuchang Ag super-large deposit, Dachang tin polymetallic ore field and Wangshe Cu-W deposit and analysis of tectonic evolution of Southeast of Yunnan Province, we propose that these deposits occurred at the same geodynamic framework as a result of large scale mineralization in South China.