木吉村斑岩铜矿成矿作用:华北克拉通中生代岩石圈减薄的响应

Mujicun porphyry copper mineralization: Response to Mesozoic thinning of lithosphere in North China Craton

木吉村铜（钼、金）矿位于华北克拉通太行山北段中生代岩浆岩带,为大型隐伏斑岩型矿床。矿体赋存于侏罗纪髫髻山组与火山岩相关的闪长玢岩次火山岩相中。木吉村髫髻山组安山岩中岩浆锆石的两组U-Pb年龄分别为（150.5±3.0）Ma和（140.8±3.0）Ma,与北京西山髫髻山组火山岩锆石U-Pb年龄范围（156.6~137.1）Ma基本一致。木吉村闪长玢岩的锆石U-Pb年龄为（141.7±1.6）Ma,代表了髫髻山火山作用晚期次火山岩相的结晶年龄。木吉村斑岩铜矿辉钼矿Re-Os等时线年龄为（142.5±1.4）Ma。结合发表的区内中生代花岗岩锆石U-Pb年龄（138~126 Ma）,新结果揭示木吉村斑岩型铜成矿作用与髫髻山火山作用相关,而与后期花岗岩浆大规模的侵位无关。木吉村斑岩成矿年龄与华北克拉通东南缘长江中下游斑岩铜矿成矿年龄（144~139 Ma）相一致,也与华北克拉通中生代动力学体制转折时间相吻合。这表明,木吉村斑岩铜矿与长江中下游铜矿带形成于相似的地球动力学背景下,即华北克拉通中生代大规模岩石圈减薄的构造背景。

The Mujicun porphyry copper deposit,a large-size concealed ore deposit,is located in northern Taihangshan（Taihang Mountains） Mesozoic magmatic belt of North China Craton（NCC）.Ore bodies occur in subvolcanic diorite porphyrites of the Jurassic Tiaojishan Formation volcanic rocks.Two peak U-Pb ages of zircons from the Tiaojishan andesites are（150.5±3.0） Ma and（140.8±3.0） Ma,respectively.This age range is generally consistent with the U-Pb age range（156.6～137.1） Ma of zircons from the Xishan Tiaojishan andesites in Beijing area.U-Pb age of zircons from Mujicun diorite porphyrites is（141.7±1.6） Ma,representing a crystallization age of subvolcanic rocks in the late phase of the Tiaojiahsn volcanism.A Re-Os isochron age of molybdenites from the Mujicun porphyry copper deposit is（142.5±1.4） Ma,similar to the zircon U-Pb age of the diorite porphyrites.In combination with available U-Pb ages（138～126 Ma）of zircons from Mesozoic granites in northern Taihangshan,the authors＇ new results reveal that the copper mineralization was well associated with the Tiaojishan volcanism rather than with the later emplacement of the large-size granitic batholiths in northern Taihangshan area.In addition,the mineralization age of the Mujicun porphyry copper deposit is similar to the ages of porphyry Cu deposits in the Yangtze River Metallogenic belt and southeastern NCC,and is roughly coeval with the geodynamic reversion of the NCC during Mesozoic.This coincidence probably indicates that the porphyry copper deposits in the NCC were formed in similar geodynamic settings characterized by large-scale thinning of the lithosphere beneath the NCC.