大别造山带宿松地体早白垩世中―基性脉岩地球化学特征.doc

大别造山带宿松地体早白垩世中―基性脉岩地球化学特征 　　文章编号2016 　　摘要：大别造山带是三叠纪华南陆块俯冲于华北陆块之下所形成的陆陆碰撞造山带，在早白垩世发育强烈的碰撞后岩浆作用。侵位于宿松群高压变质岩石中的大量中―基性脉岩是认识大陆板块深俯冲过程的壳幔相互作用和折返过程中岩石圈构造响应的重要载体之一。报道了有关宿松地体中―基性脉岩的岩石学和地球化学研究结果，探讨了其成因特征和源区演化。结果表明：中―基性脉岩总体具有安粗岩的性质，主量元素含量变化较大，SiO2质量分数介于4845%～6137%，偏基性脉岩具有偏高的MgO、Cr、Ni含量；所有脉岩样品的微量元素和稀土元素组成均一，大离子亲石元素和轻稀土元素相对富集，重稀土元素和高场强元素亏损；脉岩样品都具有相对富集的同位素组成特征，包括较高的初始N（87Sr）/N（86Sr）值（0.706 3～0.710 9），较低的εNd（t）值 （-22.7～-15.1）；初始Pb同位素比值也相对偏低，初始N（206Pb）/N（204Pb）值为15.858 5～17196 7，初始N（207Pb）/N（204Pb）值为15.207 2～15.332 1，初始N（208Pb）/N（204Pb）值为36.814 4～37.633 8， 这些特征暗示岩浆源区具有扬子板块下地壳物质的显著贡献。总之，中―基性脉岩具有高Sr含量和低Y、Yb含量，与埃达克质岩组成类似，可能指示宿松地体早白垩世中―基性脉岩的形成与增厚的造山带岩石圈拆沉及其和地幔的相互作用有关。 　　关键词：地球化学；中―基性脉岩；早白垩世；SrNdPb同位素；壳幔相互作用；拆沉作用；宿松地体；扬子板块；大别造山带 　　中图分类号：P588.13文献标志码：A 　　Geochemical Characteristics of Early Cretaceous Intermediatemafic Dykes in Susong Terrene of Dabie Orogenic Belt 　　XIE Qinglu1，2， LI Shuangqing1， HE Jianfeng1， CHEN Fukun1 　　（1. School of Earth and Space Sciences， University of Science and Technology of China， Hefei， 230026， Anhui， China； 　　2. Department of Navigation， Bengbu Naval Petty Officer Academy， Bengbu 233012， Anhui， China） 　　Abstract： Dabie orogenic belt is a typical continental collision belt by Triassic subduction and collision between Yangtze Block and North China Block. It is characterized by not only the largest exposure of Triassic ultrahighpressure metamorphic rocks in the world， but also the most profound occurrence of postcollisional Cretaceous igneous rocks. Early Cretaceous intermediatemafic dykes， intruding into highpressure metamorphic rocks of Susong terrene of Dabie orogenic belt， are important for understanding the process of mantlecrustal interaction during the deep subduction of the continental block and the tectonic respondence in the uplift. The petrological and geochemical characteristics of these intermediatemafic dykes were presented， and the petrogenesis and geological implications were discussed. The results show that the