新疆塔城别斯托别苏长辉长岩的岩石学和锆石SHRIMP年代学研究

Lithology and Zircon SHRIMP Chronology of the Biesituobie Gabbro in Tacheng,Xinjiang

塔城市南约30km的别斯托别苏长辉长岩侵入石炭纪二长花岗岩中,二者的接触部位多被农田覆盖。二长花岗岩内部存在大量辉长岩、闪长岩、花岗闪长岩、石英闪长岩、石英斑岩等包体,但没有苏长辉长岩包体。苏长辉长岩主要由透辉石-普通辉石、顽火辉石、基性斜长石(An51～70)和少量钛铁矿-磁铁矿组成。从苏长辉长岩中分选出的锆石CL图像显示典型的扇形结构(锆石中存在辉石和斜长石包体)。对两个锆石样品进行的SHRIMP年代学研究得到平均年龄分别为273.3±1.8Ma(MSWD=1.18,n=20)和272.5±2.8Ma(MSWD=0.75,n=12)。这两个年龄在误差范围内完全一致,表明别斯托别苏长辉长岩的形成时代为早二叠世晚期。在该苏长辉长岩与花岗岩接触带附近观察到的铜矿化现象,为找矿勘探提供了方向。

The Biesituobe gabbro, consisting of diopside-augite, enstatite, Ca-rich plagioclase （An： 51 -70）, and ilmenite-magnetite, intrudes into the Carboniferous monzonitic granite, located -30km of the south of Tacheng City, Xinjiang. Zircons separated from this gabbro, containing plagioclase and pyroxene inclusions, show a clear sector-zoning pattern. Zircons from two samples were dated to be 273.3±1.8Ma （MSWD = 1.18, n = 20） and 272.5±2.8Ma （MSWD = 0.75, n = 12） by SHRIMP, respectively. The two U-Pb ages are consistent to each other and represent the magma intrusion time of the Biesituobie mafic magma during the Late stage of the Early Permian epoch.