西藏墨竹工卡县洞中拉铅锌矿床花岗斑岩锆石SHRIMP U-Pb定年

Zircon SHRIMP U-Pb age of porphyry granite in the Dongzhongla lead-zinic deposit, Maizhokunggar County, Tibet

洞中拉铅锌矿床是念青唐古拉山地区扎雪-亚贵拉成矿带内新发现的矿床,矿区出露的花岗斑岩侵人体与洞中拉铅锌多金属矿床的形成密切相关.为精确限定其形成时代,笔者对洞中花岗斑岩进行单颗粒锆石SHRIMP U-Pb定年,结果显示其~（206）Pb/~（238）U加权平均年龄为（124.4±1.9）Ma（MSWD=5.09）.该年龄对应于冈底斯-念青唐古拉火山岩浆岩带东段的早白垩世岩浆活动事件（介于109～130 Ma）,与扎雪-金达铅锌多金属矿成矿带内出露的花岗类岩体年龄（120～130 Ma）一致.结合区域资料,洞中拉花岗斑岩是早白垩世弧间裂谷伸展作用下地壳挤压增厚局部熔融的产物.为念青唐古拉地区早白垩世岩浆侵位活动以及铅锌铜钼多金属矿产找矿方向研究提供了重要证据.

Located in the Zhaxue -Yaguila metallogenic belt of the Nyainqentanglha Range, Tibet, the Dongzhongla ore deposit is a newly-discovered lead-zinc polymetallic deposit. The exposed porphyry granite has an intimate relationship with the Dongzhongla ore deposit. In order to determine the accurate age of the porphyry granite in Dongzhongla, the authors employed the zircon SHRIMP U-Pb isotope dating technology and obtained the age of 124.4 ±1.9 Ma （MSWD =5.09）, indicating Cretaceous. This age is essentially in agreement with the event of magmatism in the east of the Gangdise -Nyainqentanglha volcanic -magmatic belt （from 109 Ma to 130 Ma） and the age of granites in the Zhaxue-Jinda lead-zinc polymetallic metallogenic belt. Combined with regional data, it is suggested that the Dongzhongla early Cretaceous porphyry granites resulted from the crustal thickening melting of the intra -arc rift tensional system. This age provides the important evidence for Cretaceous magmatism and helps to direct studies related to lead -zinc molybdenum -copper polymetallic ore exploration in the Nyainqentanglha Range.