西准噶尔晚古生代花岗岩类侵入体(40)~Ar/(39)~Ar热年代学

西准噶尔成矿带夹持在天山断裂与额尔齐斯断裂之间,是中亚成矿域西部的核心区域之一,广泛发育晚古生代深成岩浆活动、走滑断裂构造和斑岩铜矿、造山型金矿成矿作用。本文在西准噶尔成矿带包古图岩体、康德岩体、加曼岩体、库鲁木苏岩体、别鲁阿嘎希岩体、哈图岩体、阿克巴斯套岩体、庙尔沟岩体、克拉玛依岩体及红山岩体采集12个样品,通过黑云母和钾长石(40)~Ar/(39)~Ar阶段升温测年,给出了该地区(40)~Ar/(39)~Ar冷却年龄。其中,黑云母(40)~Ar/(39)~Ar年龄处在326~302 Ma范围内,钾长石(40)~Ar/(39)~Ar年龄为297~264 Ma,反映了西准噶尔地区晚石炭世-中二叠世的区域中温冷却历史。结合前人报道的锆石U-Pb、角闪石(40)~Ar/(39)~Ar、辉钼矿Re-Os、磷灰石裂变径迹等年龄数据,构建了西准噶尔成矿带晚古生代岩浆侵入,成矿作用与构造抬升,以及晚中生代剥露过程的整个热历史;并与区域左行走滑断裂活动的时间进行了对比,讨论了(40)~Ar/(39)~Ar冷却年龄的构造意义。

40Ar/39Ar Thermochronology of Late Paleozoic Granitoids in West Junggar (Xinjiang,China), Central Asia

The West Junggar Metallogenic Belt (WJMB) in the western part of the Central Asian Metallogenic Domain (CAMD), is located between the Tianshan fault system and the Ertix fault system. It is featured by the widespread Late Paleozoic granitic plutons, strike-slip faults, and porphyry copper and orogenic gold deposits. We collected twelve granitoid samples from the Jiaman, Kangde, Kulumusu, Bieluagaxi, Hatu, Akebasitao, Miaoergou, Baogutu, Karamay, and Hongshan plutons in the WJMB.40Ar/39Ar thermochronological analyses yield biotite40Ar/39Ar ages ranging from 326 Ma to 302 Ma and K-feldspar40Ar/39Ar ages from 297 Ma to 264 Ma, revealing regional medium-temperature cooling history in the WJMB during the Late Carboniferous to Middle Permian. Integrated with previous zircon U-Pb, amphibole40Ar/39Ar, molybdenite Re-Os and apatite fission track ages, we reconstructed the whole thermal history of the WJMB, including the Late Paleozoic magmatic intrusion, the porphyry Cu and W-Mo mineralization, and the Late Mesozoic tectonic uplifting and exhumation of the WJMB.40Ar/39Ar cooling ages are consistent with the timing of the regional sinistral strike-slip faults, showing the tectonic significance of the cooling ages. We suggest that the biotite and K-feldspar40Ar/39Ar cooling ages may record the age of the left-lateral strike-slip faulting in the WJMB.