八里棚早白垩世花岗岩锆石U-Pb年代学、地球化学特征:对桐柏—大别造山带碰撞后岩浆作用的指示  

Geochemistry and zircon U-Pb age of the Balipeng granites:Implication for the post-collision magmatism in the Tongbai-Dabie Orogen

作　　者：曾小华 孙四权 刘圣鑫 刘嘉 汪国虎 石先滨 钟石玉 杜文洋 黄桂珍 ZENG Xiaohua;SUN Siquan;LIU Shengxin;LIU Jia;WANG Guohu;SHI Xianbin;ZHONG Shiyu;DU Wenyang;HUANG Guizhen(Hubei Geological Survey,Wuhan 430074,Hubei,China;A Cademician Expert Workstations of Hubei Geological Bureau,Wuhan 430074,Hubei,China;Hubei Provincial Engineering Technology Research Center For Geological Exploration,Wuhan 430074,Hubei,China)

机构地区：[1]湖北省地质调查院,湖北武汉430074 [2]湖北省地质局院士专家工作站,湖北武汉430074 [3]湖北省地质勘查工程技术研究中心,湖北武汉430074

出　　处：《矿产勘查》2023年第3期348-359,共12页Mineral Exploration

基　　金：中国地质调查局中国矿产地质志项目(DD20160346、DD20190379);湖北省地质局科研项目:湖北省成矿地质条件及成矿规律研究(KJ2020-53);鄂东南矿集区中生代大地构造演化及控岩控矿机制研究(KJ2021-9-1);湖北省自然资源厅科技项目:桐柏—大别山地区碱性花岗岩稀有金属成矿作用(ETZ201807A08)联合资助。

摘　　要：后碰撞岩浆作用对研究大陆造山带构造的演化具有重要的意义。桐柏—大别作为典型的造山带,经历了完整的造山作用,并于中生代产生大规模的岩浆作用,对揭示桐柏—大别造山带的构造演化提供了有利条件。本文对桐柏—大别造山带八里棚花岗岩进行了锆石U-Pb年代学、全岩地球化学分析。认为八里棚花岗岩为高钾钙碱性岩石,具有高SiO_(2)(76.85%~77.14%)、低MgO(0.08%~0.27%)、富集轻稀土元素(LREE)和大离子亲石元素(LILE)(如Th、K、Rb)、亏损高场强元素(HREE)(如Ti、Ta、Nb)的特征,同时具有明显的Eu负异常(δEu=0.43~0.67),低Sr(27.4×10^(-6)~61.1×10^(-6))低Sr/Y比值(2.93~7.29),指示八里棚花岗岩为非埃达克质花岗岩。八里棚花岗岩锆石U-Pb年龄为(128±2) Ma,对应桐柏—大别造山带垮塌晚期,指示其为造山带碰撞后减薄地壳部分熔融形成。综合前人研究资料,进一步揭示了桐柏—大别造山带由早期加厚的岩石圈地壳逐渐过渡晚期减薄的岩石圈地壳的构造体系转换过程。Post-collision magmatism is a critical issue to the study of the evolution of continental orogen.As a typical orogenic belt,Tongbai-Dabie has experienced complete orogeny and developed a large amount of magmatism in the Mesozoic,which provides opportunity for revealing the tectonic evolution of the Tongbai-Dabie orogen.This paper analyzes the zircon U-Pb chronology and whole-rock geochemistry of the Balipeng granites in the Tongbai orogenic belt.The Balipeng granite show characterisitics of high-potassium calcium-alkaline rock with high SiO_(2)(76.85%-77.14%),low MgO(0.08%-0.27%)contents.They are rich in LREE and LILES(e.g.,Th,K,Rb),depleted HREE(e.g.,Ti,Ta,Nb),with obvious negative Eu anomaly(δEu=0.43-0.67),low Sr(27.4×10^(-6)-61.1×10^(-6)),low Sr/Y ratio(2.93-7.29).These indicate that Balipeng is non-adakitic granite.The zircon U-Pb age of the Balipeng granite is(128±2)Ma,which was formed in the late stage of the collapse of the Tongbai-Dabie orogen indicating that the Balipeng granite was formed by partial melting of the thinned crust after the collision of the orogenic belt.Based on previous research data,it further revealed the transformation of the Tongbai-Dabie orogent structural system,the collisional magmatism and the tectonic evolution process after the collapse stage.

关 键 词：造山带垮塌 岩浆作用 部分熔融 岩石圈减薄 八里棚地区 

分 类 号：P581[天文地球—岩石学]