西藏洞中拉铅锌矿床石英斑岩锆石U-Pb年代学研究

Zircon U-Pb age of the quartz porphyry from Dongzhongla Pb-Zn deposit in Tibet,China

探讨西藏洞中拉铅锌矿区的石英斑岩岩体归属。通过详细的地质填图,并采用LA-ICPMS锆石U-Pb法年龄测定技术,对石英斑岩进行年代学研究。通过石英斑岩样品中单颗粒锆石22个样品点的分析,得到其206Pb/238 U的加权平均年龄为126.9±1.1Ma,MSWD=0.96。这一结果否认了这套岩石单元属于始新世林子宗群帕那组的认识。区内石英斑岩岩体侵位年龄在125.8～128.0Ma,属于燕山晚期,与矿区东侧亚贵拉铅锌钼矿出露的石英斑岩的年龄基本一致,表明在120～130Ma B.P.念青唐古拉山地区发生了大规模的岩浆活动。

This paper discusses which period the quartz porphyry in the Dongzhongla Pb-Zn ore district belongs.Through the detailed geological mapping and using the high precision magmatic zircon LA-ICPMS U-Pb dating,the authors date the quartz porphyry from the Dongzhongla deposit.The dated 22 zircon grains from the quartz porphyry present that 206Pb/238U weighted mean age is 126.1±1.1 Ma（n=22,MSWD=0.96）.Thus,it denies the previous understanding that these rock units belong to the Linzizong Group Pana formation in Eocene.The crystallization of the quartz porphyry occurred between 125.8~128.0 Ma during the late Yanshanian period.This is in accordance with the age of quartz porphyry from Yaguila which located in the east of Dongzhongla.It indicates that there existed large-scale magma activity before 126 Ma in Nyanqentanglha region.