湘中紫云山花岗岩和暗色包体的源区及其地质意义:来自全岩地球化学及Sr-Nd同位素的证据  

Source area and geological significance of Ziyunshan granite and mafic microgranular enclaves in central Hunan:Evidences from whole rock geochemistry and Sr-Nd isotopes

作　　者：鲁玉龙 肖荣[2] 彭建堂 黄建中[2] 李欢 王鹏[1,2] 冷家豪[2] 刘洋 LU YuLong;XIAO Rong;PENG JianTang;HUANG JianZhong;LI Huan;WANG Peng;LENG JiaHao;LIU Yang(School of Earth Sciences and Spatial Information Engineering,Hunan University of Science and Technology,Xiangtan 411201,China;Institute of Geological Survey of Hunan Province,Changsha 410083,China;MOE Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,School of Geosciences and Info-physics,Central South University,Changsha 410083,China;State Key Laboratory of Ore Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550002,China)

机构地区：[1]湖南科技大学地球科学与空间信息工程学院,湘潭411201 [2]湖南省地质调查所,长沙410083 [3]中南大学地球科学与信息物理学院,有色金属成矿预测与地质环境监测教育部重点实验,长沙410083 [4]中国科学院地球化学研究所,矿床地球化学国家重点实验室,贵阳550002

出　　处：《岩石学报》2025年第1期135-150,共16页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41272096);湖南省自然科学基金项目(2021JJ40197);矿床地球化学国家重点实验室开放基金(202203)联合资助.

摘　　要：湘中紫云山花岗质岩体形成于晚三叠世,近年来因其周边众多金属矿床的发现而备受关注。岩体内含有丰富的暗色包体(MMEs),为研究其源区和形成过程提供了一个重要的窗口。本文对紫云山暗色包体进行了全岩主、微量元素分析,并对紫云山花岗岩和暗色包体进行了Sr-Nd同位素分析。暗色包体主要为闪长质-花岗闪长质,SiO_(2)含量在55.24%~68.72%(平均为63.758%),K_(2)O含量为1.22%~6.33%(平均值为2.76%),属于钙碱性系列至高钾钙碱性系列岩石。暗色包体的(^(87)Sr/^(86)Sr)i值为0.714943~0.720623,ε_(Nd)(t)值为-9.53~-6.5,t DM2为1.53~1.78 Ga;主体花岗岩的(^(87)Sr/^(86)Sr)_(i)值为0.718160~0.724384,ε_(Nd)(t)值为-7.4~-8.2,二阶段模式年龄t DM2为1.60~1.67Ga;补体花岗岩的(^(87)Sr/^(86)Sr)_(i)值为0.735888~0.745734,ε_(Nd)(t)值为-10.1~-10.9,二阶段模式年龄t_(DM2)值为1.82~1.89Ga。研究表明:紫云山花岗岩主要来源于变杂砂岩熔融的壳源岩浆,并混合了部分富集幔源岩浆;其中主体花岗岩相较补体花岗岩含有较多的幔源组分,而紫云山暗色包体主要来源于富集地幔。紫云山花岗岩和暗色包体可能是印支期华南板块受周缘板块碰撞挤压后岩石圈伸展减薄,底侵的高温幔源岩浆注入到壳源长英质岩浆房后,两者混合不均的产物。在湘中地区,印支晚期花岗岩与其附近的金(锑)、钨等矿床存在密切的时、空联系,可能具有良好的成矿潜力;该区印支晚期花岗岩的成岩-成矿作用的强度远超传统认识,在找矿过程中需加以重视。The Late Triassic Ziyunshan granitic pluton in central Hunan has attracted much attention due to the discovery of precious metal deposits in its surrounding areas.Abundant mafic microgranular enclaves(MMEs)in this pluton provided a valuable window for studying the source,formation and mineralization of the Indosinian plutons in South China.In this study,the whole rock geochemistry and Sr-Nd isotopic compositions of the MMEs within the Ziyunshan pluton were analyzed.These MMEs are mainly diorite or granodiorite with SiO_(2)and K_(2)O contents of 55.24%~68.72%(avg.63.75%)and 1.22%~6.33%(avg.2.76%),respectively,belonging to the calc-alkaline to high-K calc-alkaline series.For the analyzed samples of the MMEs,the ^(87)Sr/^(86)Sr ratios range from 0.714943 to 0.720623,theε_(Nd)(t)values are between-9.53 and-6.5,and the two-stage depleted mantle model ages(t_(DM2))are 1.53~1.78Ga.For those of the main part of granite,the ^(87)Sr/^(86)Sr ratios range from 0.718160 to 0.724384,theε_(Nd)(t)values are between-7.4 and-8.2,and the t_(DM2)are 1.63~1.67Ga.While for those of the complement granite,the ^(87)Sr/^(86)Sr ratios,ε_(Nd)(t)values and the t DM2 are 0.735888~0.745734,-7.4~-8.2 and 1.82~1.89Ga,respectively.The results indicate that the Ziyunshan granite is mainly derived from the melted crustal magma of metagreywacke mixed with some enriched mantle magma.The main granites contain more mantle-derived components than the complement ones,while the MMEs of Ziyunshan are mainly derived from the enriched mantle.The Ziyunshan granite and the MMEs may be the result of the lithosphere extension and thinning of the South China Plate in the Indosinian by the collision and extrusion of the peripheral plates.During these processes,the high temperature mantle-derived magma was injected into the crustal-derived felsic magma chamber,mixed with the later,and finally formed the pluton.In central Hunan,the Late Indosinian granites have a close temporal and spatial relationship with the gold(antimony)and tungsten deposits,indicating they

关 键 词：SR-ND同位素 岩浆源区 成矿效应 暗色包体 湘中 

分 类 号：P588.121[天文地球—岩石学] P597.2[天文地球—地质学]