河北雾灵山杂岩体锆石Hf同位素特征及其区域对比研究  

The Hf Isotopic Characteristics of the Zircons from Wulingshan Complex in Hebei and Regional Comparative Study

作　　者：陈春良[1,2] 江思宏[2] 梁清玲[2] 刘源[2,3] 韩宁[2] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]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 [3]中国地质大学(武汉)地球科学学院,湖北武汉430074

出　　处：《现代地质》2014年第4期663-673,共11页Geoscience

基　　金：国家自然科学基金项目(41030421;41273061)

摘　　要：雾灵山杂岩体是位于华北克拉通北缘河北省兴隆县境内的一个出露面积为230 km2的大岩基，岩体主要由似斑状碱长正长岩、碱性石英正长岩和碱长正长斑岩组成。对该杂岩体中最早侵位的似斑状碱长正长岩的3件样品进行了锆石U-Pb测年和原位Hf同位素测试，获得的等时线年龄分别为（128.0±0.6）Ma、（127.3±1.2）Ma和（126.8±0.4） Ma，表明该岩体最早侵位于早白垩世；同时，两阶段Hf模式年龄介于1.13～1.75 Ga，εHf（t）值为-7.8～1.7。通过对似斑状碱长正长岩εHf（t）值及其中暗色包体岩相学分析，表明该岩石源区岩浆可能是由地壳重熔形成的花岗质岩浆、岩石圈富集地幔以及亏损地幔岩浆混合形成。通过对华北克拉通北缘早白垩世不同地区A型花岗岩的εHf（t）值的对比分析表明，这些A型花岗岩的源区物质来源具有多元性，并随着时间演化，A型花岗岩中亏损地幔的成分贡献越来越多，表明这个时期大规模的岩石圈减薄近于完成，亏损地幔物质开始上涌，并直接参与了岩浆活动。Located in Xinglong County of Hebei Province,the northern margin of North China Craton,Wuling-shan complex is a batholith with an outcrop area of 230 km2 .The complex is mainly composed of porphyry-like alkali syenite,alkaline quartz-syenite and alkali feldspar syenite porphyry.The zircon U-Pb dating for 3 samples of the earliest emplaced porphyry-like alkali syenite in the complex yielded three weighted mean ages of （128.0 ±0.6）Ma,（127.3 ±1.2）Ma and （126.8 ±0.4）Ma,respectively.It shows that the complex was intruded in the Early Cretaceous.The in situ Hf isotopic analyses of the zircons gave the two-stage model ages ranging from 1.13 to 1.75 Ga,while theεHf（t）values from -7.8 to 1.7.TheεHf（t）value combined with the petrog-raphy of dark enclave of the porphyry-like alkali syenite indicates that the Wulingshan complex was formed by mixing of different magma from crust-,lithosphere enriched mantle- and depleted mantle-derived melts.By comparing the εHf（t）values of different Early Cretaceous A-type granites occurring in the northern margin of North China Craton,we can conclude that these A-type granites were derived from different sources,with more contribution of depleted mantle composition as the time evolution.It suggests that the large-scale lithospheric thinning almost finished at that time,while the depleted mantle materials started upwelling and were involved in the magmatic activity.

关 键 词：锆石U-PB测年 HF同位素 A型花岗岩 雾灵山 河北 

分 类 号：P588.12[天文地球—岩石学] P597[天文地球—地质学]