新疆觉罗塔格小热泉子组火山岩的时代探讨

新疆东天山觉罗塔格地区广泛分布着石炭系-二叠系火山岩-沉积岩地层,小热泉子组是其中的一套以火山岩为主的地层.前人依据与之接触的底坎尔组中的中石炭世化石,将小热泉子组划为早石炭世.对觉罗塔格南部的小热泉子铜矿的研究,不同学者得出了差别较大的同位素年龄,而北部的小热泉子组目前还没有同位素年龄报道.我们对北部的底坎尔和干沟两地的小热泉子组火山岩进行了锆石SHRIMP测年,得到了271～275 Ma的年龄.这些测年数据与近几年其他学者的数据一致,表明早二叠世的岩浆活动比原来认为的更广,小热泉子组的时代应该属于早二叠世,其他地层单元的时代及其先后关系也需要重新认识.

A discussion on the age of volcanic rocks in Xiaorequanzi Formation, Queletag, Xinjiang

Xiaorequanzi Formation is a unit of volcanic rock among Carboniferous-Permian volcano-sedimentary rocks which are widely exposed in Queletag, East Tianshan, Xinjiang. It has been divided into Early Carboniferous by referring the neigboring Digar Formation which is defined to Middle Carboniferous by fossil age. Different ages have been given on Xiaorequanzi copper mine in the southern part of Queletag. In the northern part, isotopic chronology data is absent where we dated it using SHRIMP. Isotopic chronology evidence shows that the volcanic rocks and dyke at Digar and Ganggou are of 271~275Ma. These ages are consistent with the recent results in adjacent region by other geologists. According to present evidence, Xiaorequanzi Formation ought to be Early Permian and other strata units and their relative age may be renewed.