塔里木盆地塔参1井底部花岗闪长岩的^(40)Ar-^(39)Ar年代学研究

^(40)Ar-^(39)Ar eeochronoloev of the granite and diorite revealed at the bottom of Tacan 1, the deepest well in China.

我国陆上最深的钻井——塔参1井,井深7200m,其底部钻遇的是一分布有闪长岩捕虏体的花岗闪长岩体。我们采集花岗闪长岩样品和闪长岩样品,分选角闪石单矿物进行^(40)Ar-^(39)Ar定年。花岗闪长岩的加^(40)Ar-^(39)Ar坪年龄为932.3±0.6Ma和891.0±1.9Ma,相应的等时年龄分别为933.8±6.8Ma和892.2±32.7Ma;闪长岩^(40)Ar-^(39)Ar坪年龄为1195.7±1.0Ma,等时年龄为1199.4±6.4Ma。本项研究结果表明,塔参1井底部的火成岩为一花岗闪长岩岩体,侵位时代为新元古宙早期;闪长岩形成于中元古宙晚期,是花岗闪长岩中的捕虏体。塔里木盆地腹地存在前寒武纪古老陆壳基底,该岩体就是其重要的组成部分。

Tacan 1 ('TC1' for short) located at the central part of Tarim Basin is 7200m in depth, the deepest well in China. It revealed granite and diorite at the bottom. Two hornblende samples were collected from the granite and one from the diorite for 40Ar-39Ar dating. The two samples from granite yielded plateau ages of 932.3±0.6Ma and 891.0±1.9Ma, isochron ages of 933. 8±6. 8Ma and 892. 2±32. 7Ma, respectively. The sample from diorite yielded plateau age of 1195.7±1.0Ma and isochron age of 1199.4 ±6.4Ma. These results indicate that the igneous rocks revealed at the bottom of TC1 are from a granite body intruded in early Neoproterozoic, and the diorite was formed in late Mesoproterozoic and distributed in the granite as xenoliths. TC1 granite body is possibly a component of Tarim Precambrian basement.