华北地台南缘张士英岩体的锆石SHRIMP U-Pb测年、Hf同位素组成及其地质意义  

SHRIMP zircon U-Pb ages and Hf isotopic compositions of Zhangshiying intrusive complex in the southern margin of the North China Craton and their geological implications

作　　者：向君峰[1,2] 赵海杰[1] 李永峰 程彦博[2] 高亚龙[2] 侯可军[1] 董春艳[4] 李向前[2] 

机构地区：[1]中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质大学(北京)地球科学与资源学院,北京100083 [3]河南省有色金属地质矿产局,郑州450052 [4]北京离子探针中心,北京100037

出　　处：《岩石学报》2010年第3期871-887,共17页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(40434011);全国危机矿山接替资源找矿项目(20089949和200841019);中央级公益性科研院所基本科研业务费专项资金(K0816)资助

摘　　要：张士英岩体位于华北地台南缘,岩石类型包括钾长花岗岩、似斑状花岗岩和石英斑岩脉,其中只在钾长花岗岩中发育有暗色岩石包体,在包体和寄主岩中发育反映岩浆混合作用的岩石结构。钾长花岗岩、似斑状花岗岩和石英斑岩脉的SHRIMP锆石U-Pb年龄分别为107.3±2.4Ma、106.7±2.5Ma和101±3Ma。锆石Hf同位素分析结果显示,钾长花岗岩的锆石εHf(t)为-15.96～-20.80,单阶段模式年龄(tDM1)为1396～1643Ma,两阶段模式年龄(tDM2)为1880～2018Ma;似斑状花岗岩的锆石εHf(t)为-18.97～-22.18,tDM1为1512～1640Ma,tDM2为1925～2080Ma;除了一粒年龄为2.6Ga的锆石具有εHf(t)为-0.71、tDM1为2943Ma和tDM2为3036Ma的组成,石英斑岩的锆石εHf(t)为-23.41～-27.95,tDM1为1678～1896Ma,tDM2为2144～2330Ma。这些数据暗示,除了存在少量太古宙地壳物质的贡献外,张士英岩体的物质来源可能主要为1.9～2.3Ga期间形成的新生地壳,但也不排除古老地壳与富集地幔源混合的可能。综合分析前人研究成果表明,在太平洋板块俯冲方向发生转变的过程中,先存断裂带发生拉张。张士英岩体与中国东部同期岩浆活动一起可能形成于这种受断裂带控制的伸展环境。Zhangshiying intrusive complex (ZIC),consisting of K-feldspar granite,granite porphyry and quartz porphyry,is located in the southern margin of the North China Craton. The mafic enclaves are merely in K-feldspar granite and have textures indicating magma mixing. We obtained their SHRIMP zircon U-Pb ages of 107.3±2.4Ma,106.7±2.5Ma and 101±3Ma for K-feldspar granite,granite porphyry and quartz porphyry,respectively. According to zircon Hf isotope analyses,their εHf(t) values are-15.96^-20.80,-18.97^-22.18 and-23.41^-27.95 and their corresponding Hf two-stage model ages(tDM2) are 1880~2018 Ma,1925~2080Ma and 2144~2330 Ma. One exception is the zircon inherited Archean information with 207Pb/206Pb age of 2.6 Ga,-0.71 of εHf(t) and 3.0 Ga of tDM2. These data suggest that the source of ZIC is mainly either juvenile crust formed at 1.9~2.3Ga or an enriched mantle source with the contribution of Archean continental crust. On integration of regional research results,we suggest that ZIC could form at a regional lithospheric extensional setting which is confined to the existing NE-SW or NW-SE fault zones and is triggered by the drifting direction of the Pacific plate changing to southwest ward.

关 键 词：华北地台南缘 张士英岩体 锆石U-PB测年 锆石HF同位素 白垩纪 太平洋板块 

分 类 号：P588.121[天文地球—岩石学]