辽宁盘岭矿集区花岗岩锆石SHRIMP U-Pb年龄、Hf同位素组成及地质意义

辽宁盘岭矿集区产出在辽吉裂谷中段的草河口—草河城—黑峪一带,是一处典型的古元古代沉积盆地和多金属矿集区。矿区内发育有早白垩世的北大砬子岩体和古元古代高丽墩台岩体,与本区的矿化作用密切相关。北大砬子岩体锆石SHRIMP U-Pb年龄加权平均值为(123.9±2.2)Ma,高丽墩台岩体锆石SHRIMP U-Pb年龄加权平均值为(1 872±13)Ma。北大砬子岩体εHf(0)为负值,εHf(t)为负值(-16.86~-10.95),说明北大砬子岩体形成时壳源物质成分占主导地位,单阶段Hf模式年龄(TDM)平均为1 339 Ma,两阶段Hf模式年龄(TDMC)平均为2 043 Ma;高丽墩台岩体εHf(0)为负值,εHf(t)为正值(0.29~4.64),说明高丽墩台岩体形成时壳源物质成分占主导地位,并有地幔物质混染,单阶段Hf模式年龄(TDM)平均为2 171 Ma,两阶段Hf模式年龄(TDMC)平均为2 355 Ma。结合岩石地球化学特征得出:北大砬子岩体具有高钾钙碱性岩浆岩特征,为较高分异的过铝质I型花岗岩,是底侵岩浆提供热动力使下地壳物质部分熔融的产物,属于晚中生代大陆边缘岩浆弧环境,其与进入早白垩世古太平洋板块俯冲作用密切相关,岩浆活动直接影响盘岭矿集区内一期铜、铅、锌、钼等矿化作用;高丽墩台岩体具有低钾(拉斑)岩浆岩特征,为较高分异的过铝质I型花岗岩,是热的玄武质熔体加热下地壳使之熔融的产物,且可能有地幔物质贡献,岩体侵入诱发的一系列断裂(包括层间断裂)控制着矿集区内矿脉及岩脉的空间分布。

Zircon SHRIMP U-Pb Age and Hf Isotope of Granite in Panling Ore Concentration Area in Liaoning and Its Geological Significance

The Panling ore concentration area is a typical paleoproterozoic sedimentary basin and a multi-metal ore-concentrated area,located in the zone of Caohekou-Caohecheng-Heiyu,also in the middle section of Liaoning-Jilin rift.The Beidalazi rock developed in the Early Cretaceous and the Gaoliduntai rock developed in Paleoproterozoic are closely related with the mineralization in this ore-concentrated area.The weighted average of the zircon SHRIMP U-Pb age of the Beidalazi rock is (123.9±2.2) Ma,and the weighted average of the zircon SHRIMP U-Pb age of the Gaoliduntai rock is (1 872±13) Ma.The ε Hf(0) value of the Beidalazi rock is negative,and theεHf(t) is (-16.86-10.95),that indicate its shell material domination when the Beidalazi rock formed.The single stage Hf model age (TDM) is 1 339 Ma,and the two-stage Hf model age (TDMX) is 2 043 Ma.The εHf(0) value of Gaoliduntai rock is negative,and the εHf (t) iS 0.29-4.64,that indicate the shell material domination when the Gaoliduntai rock formed.The single stage Hf model age (TDM) is 2 171 Ma,and the two-stage Hf model age (TDMC) is 2 355 Ma.The geochemical results show that:.The Beidalazi rock is of high-K calc-alkaline series and highly differentiated aluminous Ⅰ-type granite,and it is a thickened and molten product of the lower crust with a serious magma contamination in the Late Mesozoic continental margin magmatic arc environment resulted from the Early Cretaceous subduction of the paleo Pacific plate;The magmatic activity directly led to the mineralization of copper,lead,zinc and molybdenum etc.in Panling area.While the Gaoliduntai rock is a kind of low potassium magmatite (tholeiitic) and highly differentiated aluminous Ⅰ-type granite caused by the melting of the basaltic melt to heat the crust to melt,and it may have the contribution of mantle material invasion induced by a series of faults (including inter-layer fractures) to control the mineralization and distribution of the ore veins.