滇西兰坪盆地白秧坪Pb-Zn-Cu-Ag多金属矿床东矿带成矿年代学探讨

An investigation of metallogenic chronology of eastern ore block in Baiyangping Pb-Zn-Cu-Ag polylmetallic ore deposit, Lanping Basin, western Yunnan Province

白秧坪Pb-Zn-Cu-Ag多金属矿集区夹持于金沙江和澜沧江断裂之间,隶属兰坪盆地北部,分为东、西2个矿带。文章采用闪锌矿、方铅矿的Rb-Sr法和成矿阶段方解石的Sm-Nd法,对白秧坪Pb-Zn-Cu-Ag多金属矿床东矿带华昌山和下区五矿段进行了成矿年代厘定,获得方铅矿以及闪锌矿和方铅矿的矿物组合Rb-Sr等时线年龄为(32.8±1.5)Ma,方解石的Sm-Nd等时线年龄为(33.32±0.43)Ma。研究表明,通过对特定矿床的主要矿石矿物采用Rb-Sr法和Sm-Nd法获得的年龄在误差范围内是一致的,从而起到了相互验证的作用,并对矿床的成矿背景具有一定的指示性。通过成矿年龄的探讨,认为东矿带铅锌为主的矿化期主要产生于青藏高原东缘晚碰撞阶段(40~26)Ma,伴随印度-亚洲大陆碰撞造山,形成逆冲推覆构造和赋矿地层,控制了Pb-Zn矿床的形成和发育。该期Pb-Zn矿床与兰坪盆地金顶和西矿带Pb-Zn矿床、囊谦盆地Pb-Zn矿床和沱沱河盆地Pb-Zn矿床具有一定的可比性。

As one part of the northern Lanping Basin, the Baiyangping Pb-Zn-Cu-Ag polymetallic ore district is located between the Jinshajiang fault and the Lancangjiang fault. On the basis of the sphalerite/galena Rb-Sr and calcite Sm-Nd dating, this study provides preferable ore-forming ages （32.8±1.5） Ma and （33.32±0.43） Ma for the Huachangshan and Xiaquwu ore plates in Baiyangping Cu-Pb-Zn-Ag polymetallic ore district, western Yunnan Province, China. The results suggest that the Rb-Sr and Sm-Nd dating data are consistent within the error range, which, in addition, has certain instruction significance for understanding the deposit metallogenic background. Moreover, due to the age of mineralization, Pb-Zn mineralization period in eastern ore belt mainly produced between 40 Ma and 26 Ma when late collision appeared in east edge of the Qinghai-Tibet plateau. Thrust-nappe system and hosted ore strata were formed due to the collision and orogenesis between India and Asia, and then Pb-Zn ore deposits occurred. This period of Pb-Zn ore deposit can be compared with other similar deposits in Jingding, Nangqian, and Tuotuohe.