云南清水河早古生代过铝质花岗岩的发现及其对保山地块岩石圈地幔拆沉的限定  

Discovery of Early Palaeozoic peraluminous granites the Qingshuihe area of Yunnan Province and constraints on the influence of lithospheric mantle delamination in the Baoshan block

作　　者：李光洁 陈永清[1] 尚志 LI Guangjie;CHEN Yongqing;SHANG Zhi(School of Earth Science and Resources,China University of Geosciences(Beijing),Beijing 100083,China)

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

出　　处：《地质通报》2022年第4期590-610,共21页Geological Bulletin of China

基　　金：国家自然科学基金项目《成矿系统自组织临界性与矿床定位预测》(批准号:41972312);《深部致矿异常信息提取与高精度数字找矿模型建立》(批准号:41672329);国家重点研发计划课题《“三联式”数字找矿模型与深部定量成矿预测》(编号:2016YFC0600509);中国地质调查局项目《云南个旧大型—超大型Sn-Cu-多金属矿床成矿地球动力学背景、过程和定量评价》(编号:1212011220922)。

摘　　要：保山地块早古生代过铝质花岗岩的岩石成因尚存在争议,为进一步探讨岩石成因,对云南清水河花岗岩开展了锆石SHRIMP U-Pb定年及岩石地球化学研究。结果表明,清水河花岗岩主要由二云母花岗岩、黑云母花岗岩组成。二云母花岗岩岩浆结晶年龄为473~462 Ma,黑云母花岗岩岩浆结晶年龄为479 Ma,侵位时代都为早古生代。含较高的SiO_(2)(67.48%~74.03%)、(Na_(2)O+K_(2)O)-Ca_(2)O(4.47%~6.46%),A/CNK>1.1,为钙碱性强过铝质花岗岩;均富集Pb、大离子亲石元素Rb、K等,相对亏损高场强元素,显示明显的负Eu异常(δEu=0.31~0.54)。Sr-Nd-Pb同位素及地球化学研究表明,清水河花岗岩均显示S-型花岗岩特征,其源岩物质为古老陆壳富粘土的泥质岩,受到部分幔源物质的混入。清水河花岗岩与双脉地花岗岩存在可对比性,可能由460~479 Ma岩石圈地幔拆沉作用形成。The petrogenesis of the Early Palaeozoic peraluminous granites in the Baoshan block remains controversial.This study applied the comprehensive methods of zircon SHRIMP U-Pb dating,Sr-Nd-Pb isotopic and bulk-rock analyses to probe the genesis and magma source of the granites from the Qingshuihe area in the Baoshan block.The results show that the Qingshuihe granites are consist of two-mica granite and biotite granite.The ages of two-mica granite and biotite granite are 473~462 Ma and 479 Ma,respectively.These rocks belonging to the peraluminous S-type granite(A/CNK>1.1)have high SiO_(2)(67.48%~74.03%)content.The values of(Na_(2)O+K_(2)O)-Ca_(2)O range from 4.47%to 6.46%,exhibiting calc-alkaline characteristics.The two-mica granite and biotite granite have similar chondrite-normalized REE patterns and primitive mantle normalized trace element patterns,such as enriched in LILEs(e.g.,Rb,K)and Pb,and depleted in HFSEs,with negative Eu anomalies(δEu=0.31~0.54).The geochemical signatures and Sr-Nd-Pb isotopes indicate that the Qingshuihe granites were derived from anatexis of ancient metasedimentary rocks with small amount of mantle components.The Qingshuihe granites are geochemically comparable to the Shuangmaidi granites and both of them were formed in a post-orogene setting where the thickened lithospheric mantle detached due to the amalgamation of exotic microcontinents onto the East Gondwana margin.

关 键 词：早古生代 过铝质花岗岩 SHRIMP锆石U-PB定年 地球化学 SR-ND-PB同位素 保山地块 地质调查工程 

分 类 号：P618.4[天文地球—矿床学] P597[天文地球—地质学]