越南昆嵩地体早古生代花岗岩地球化学特征及对三岐-福山洋俯冲的响应  

Subduction of the Tam Ky-Phuoc Son Ocean in the Kontum Complex,Central Vietnam:Geochronological and Geochemical Constraints from the Early Paleozoic Granites

作　　者：赖宗婷 张玉芝 余小清 钱鑫 Pham Trung Hieu 徐畅 王岳军 LAI Zongting;ZHANG Yuzhi;YU Xiaoqing;QIAN Xin;PHAM Trung Hieu;XU Chang;WANG Yuejun(Guangdong Provincial Key Lab of Geodynamics and Geohazards/School of Earth Sciences and Engineering,Sun Yat-sen University,Zhuhai 519082,Guangdong,China;Southern Marine Science and Engineering,Guangdong Laboratory(Zhuhai),Zhuhai 519082,Guangdong,China;University of Science VNU-HCM,227 Nguyen Van Cu Street,Ho Chi Minh,Vietnam)

机构地区：[1]中山大学地球科学与工程学院/广东省地球动力作用与地质灾害重点实验室,广东珠海519082 [2]南方海洋科学与工程广东省实验室(珠海),广东珠海519082 [3]University of Science VNU-HCM,227 Nguyen Van Cu Street,Ho Chi Minh,Vietnam

出　　处：《大地构造与成矿学》2024年第6期1451-1467,I0035-I0038,共21页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(42372250、42330302、41972235);国家重点研发计划项目(2023YFF0803701)联合资助

摘　　要：昆嵩地体位于印支陆块东部,广泛发育早古生代岩浆作用,是了解东南亚原特提斯洋演化的关键地区。但长久以来该地区原特提斯洋的俯冲极性与俯冲时间争议较大。本文对该地体中一套早古生代花岗岩进行了岩相学、锆石U-Pb年代学、锆石原位Hf同位素以及全岩主量、微量元素和Sr-Nd-Pb同位素研究。年代学结果显示,该套花岗岩的结晶年龄为446~440 Ma。花岗岩样品的K_(2)O含量为2.14%~5.92%,Na_(2)O+K_(2)O含量为5.49%~8.25%,显示高钾钙碱性特征,A/CNK值为1.03~1.18,为过铝质S型花岗岩。样品均显示明显的大离子亲石元素(如Rb、Th和U等)富集以及高场强元素(如Nb、Ta和Ti等)亏损特征,具有强烈的Eu负异常(δEu=0.23~0.69)。样品中锆石的原位Hf同位素组成变化范围较大(ε_(Hf)(t)=-19.84~+1.99),Hf同位素二阶模式年龄为新太古代-中元古代(t_(DM2)=2.7~1.3 Ga),且具有富集的全岩Nd同位素组成(ε_(Nd)(t)=-10.3~-6.5)。岩石的地球化学特征显示该套早古生代花岗岩是古老变沉积岩和基性变火成岩部分熔融的产物。结合区域地质研究表明,越南中部昆嵩地块早古生代花岗岩形成于印支陆块内部原特提斯三岐-福山洋南向俯冲作用下的岛弧背景。Previous studies of the Proto-Tethys Ocean have mainly focused on the Kunlun,Qilian,and Qinling regions.The Early Paleozoic magmatism of the Kontum massif located east of the Indochina Block may provide key evidence for the subduction and extinction times of the Proto-Tethys Ocean in Southeast Asia.In this study,a set of Early Paleozoic granites was identified in the Kontum massif,Central Vietnam.The geochronological results of the four granitic samples indicate crystallization ages of 446-440 Ma.The granite samples showed a wide range of zircon Hf isotopic compositions(ε_(Hf)(t)=-19.84 to+1.99),with t_(DM2) of 2.7 to 1.3 Ga.They exhibit high-K calc-alkaline geochemical characteristics(K_(2)O=2.14%-5.92%,Na_(2)O+K_(2)O=5.49%-8.25%)with A/CNK values of 1.03-1.18,indicating that these granite samples belong to peraluminous(S-type)granites.The samples show strongly negative Eu anomalies(δEu=0.23-0.69),enriched LILEs,but depleted HFSEs(Nb,Ta and Ti).In addition,the samples have(^(87)Sr/^(86)Sr)i ratios ranging from 0.71533 to 0.71711,and ε_(Nd)(t)between-10.3 and-6.5.These geochemical features imply that the granites were derived from the partial melting of meta-igneous and meta-sedimentary rocks.Combined with the regional geological data,we propose that the Early Paleozoic granites in the Kontum massif formed in an arc setting,responding to the southward subduction of the Tam Ky-Phuoc Son Ocean in the Indochina interior.

关 键 词：昆嵩地体 早古生代 S型花岗岩 原特提斯洋 三岐-福山洋 俯冲作用 

分 类 号：P581[天文地球—岩石学] P597[天文地球—地质学]