湖南黄沙坪铅锌多金属矿床的Re-Os同位素等时线年龄及其地质意义

Re-Os isotopic chronology of molybdenites in Huangshaping lead-zinc deposit,southeast Hunan,and its geological implications

黄沙坪铅锌多金属矿床赋存在下石炭统石磴子组灰岩与花岗斑岩接触带及附近的层滑断裂系统中，成因上与黄沙坪花岗质岩石关系密切。其成矿时代以往都是用矿体附近的花岗质岩石（花岗斑岩、石英斑岩等）或蚀变矿物年龄来间接推断的。文章采用高精度的辉钼矿Re-Os等时线定年法，直接测得矽卡岩型矿体的矿化年龄为（153．8±4．8）Ma，与前人获得的含矿矽卡岩中金云母的K-Ar年龄（153～157Ma）一致。结合黄沙坪岩体及含矿矽卡岩型矿体的稀土及微量元素地球化学特征，得出以下认识：该矿床的成矿年龄在154Ma左右；成矿作用与花岗斑岩关系密切，它们都是华南燕山早期大规模成岩成矿作用高峰期的产物。

The Huangshaping lead-zinc polymetallic deposit in southeast Hunan is genetically related to the intrusion of Huangshaping granitic rocks and occur in the contact zone between the granodioritic porphyry and the limestone of Lower Carboniferous Shidengzi Formation as well as in the neighboring bedding-plane fault zone. Previously, the metallogenic epoch of the deposit was indirectly deduced by the ages of such nearby granitic rocks as granite porphyry and quartz porphyry or altered minerals. Based on the Re-Os isochron method of molybdenites, this paper measured directly the ore-forming age from skarn ore in the Huangshaping deposit, and got a Re-Os age of （ 153.8 ± 4.8）Ma, which is in accordance with the previous K-Ar age of 153- 157 Ma obtained from phlogopite in the ore-bearing skam of the deposit. Combined with related rare earth element and trace element geochemistry of Huangsbaping granites and ore-bearing skarn, it is concluded in this paper that the age of 154 Ma should represent the metaUogenie epoch of the deposit, and that there existed a close relationship between the ore-forming process of the deposit and the granite porphyry, which were both formed during the peak stage of Early Yanshanian large-scale rock-forming and ore-forming activities in South China.