豫西熊耳山地区五丈山岩体成因与构造意义:岩石地球化学和Sr-Nd-Pb同位素约束  

Petrogenesis and Tectonic Significance of the Wuzhangshan Pluton in Xiong’ershan,Western Henan Province:Constraint from Petrogeochemistry and Sr-Nd-Pb Isotopes

作　　者：饶世成 王长明[1,2] 贺昕宇 石康兴 祝佳萱 陈奇 段泓羽 李朋伟 RAO Shicheng;WANG Changming;HE Xinyu;SHI Kangxing;ZHU Jiaxuan;CHEN Qi;DUAN Hongyu;LI Pengwei(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Beijing 100083,China;China Non-ferrous Metals Resource Geological Survey,Beijing 100012,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 [2]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [3]有色金属矿产地质调查中心,北京100012

出　　处：《现代地质》2020年第6期1230-1244,共15页Geoscience

基　　金：国家重点基础研究发展计划项目(2015CB452606);中国地质大学地质过程与矿产资源国家重点实验室科技部专项(MSFGPMR201804);“111计划”项目(BP0719021)。

摘　　要：为解析中国东部燕山期岩浆作用过程和岩石成因机理,选取熊耳山地区五丈山岩体开展岩相学、全岩主量和微量元素地球化学和全岩Sr-Nd-Pb同位素研究。五丈山岩体主要岩性为黑云角闪二长花岗岩,具有高硅(SiO2=66.44%~71.71%)、富碱(Na2O+K2O=9.8%~10.06%)、较富Al2O3(14.52%~15.63%)以及贫TFeO(1.71%~3.47%)、CaO(0.51%~2.56%)和MgO(0.19%~0.59%)等特征,为准铝质钾玄岩系列。该岩体富集LREE、K、Sr、Pb、Zr、Hf等元素,亏损HREE、Nb、Ta、Ti、P等高场强元素,具微弱Eu正异常(δEu=1.00~1.14,均值为1.07),为I型花岗岩。全岩Sr-Nd同位素分析结果显示,(^87Sr/^86Sr)i值较高(0.7073~0.7080),εNd(t)值为-20.5^-17.9,Nd的二阶段模式年龄为2599~2389 Ma。全岩Pb同位素组成变化范围窄(^206Pb/^204Pb=17.305~17.754,^207Pb/^204Pb=15.427~15.481,208Pb/204Pb=37.766~37.999),显示源区物质以古老的壳源物质为主。五丈山岩体具有高Sr/Y(40.85~236.72)和La/Yb(19.34~30.46)比值,显示出埃达克质岩石特征,MgO、Cr、Ni含量低,Mg^#值较小。研究结果指示五丈山岩体由加厚下地壳部分熔融产生,可能与扬子板块的北向陆内俯冲有关。To analyze the magma origin and mechanism of the Yanshanian magmatism in eastern China,the authors conducted a study on the petrography,Sr-Nd-Hf isotope systematics,whole-rock major and trace element geochemistry of the Wuzhangshan pluton in Xiong’ershan.The Wuzhangshan pluton consists of biotite hornblende monzogranite,which is characterized by high SiO2(66.44%-71.71%)and alkali contents(Na2O+K2O=9.8%-10.06%).The rocks contain relative high Al2O3(14.52%-15.63%),and low TFeO(1.71%-3.47%),CaO(0.51%-2.56%)and MgO(0.19%-0.59%),indicating their shoshonitic and metaluminous nature.The samples are enriched in LREEs,K,Sr,Pb,Zr,and Hf,but depleted in high field strength elements(HFSEs)such as HREEs,Ta,Nb,P,and Ti.These rocks have no obvious Eu anomaly(δEu=1.00-1.13)and with I-type granite characteristics.They have(^87Sr/^86Sr)i=0.707,3 to 0.708,0,εNd(t)=-20.5 to-17.9,and TDM2=2,599 to 2,389 Ma.Lead isotope compositions are similar(^206Pb/^204Pb=17.305-17.754;^207Pb/^204Pb=15.427-15.481;^208Pb/^204Pb=37.766-37.999),indicating that rocks were sourced from ancient crust material.These rocks have high values of Sr/Y(40.85-236.72)and La/Yb(19.34-30.46),indicating adakite-like features.The low MgO,Cr,and Ni contents and low Mg^#values indicate that the monzogranite was formed by partial melting of the thickened lower crust,probably related to the north-dipping intracontinental subduction of the Yangtze plate.

关 键 词：五丈山岩体 SR-ND-PB同位素 地球化学 岩石成因 熊耳山地区 

分 类 号：P588.1[天文地球—岩石学] P597[天文地球—地质学]