华南陆块东部中生代基性岩浆活动及其构造启示  

Mesozoic mafic magmatism in the eastern South China Block and its implication

作　　者：甘成势 钱鑫 张玉芝 王岳军 Chengshi Gan;Xin Qian;Yuzhi Zhang;Yuejun Wang(Guangdong Provincial Key Laboratoryof Geodynamics and Geohazards,Schoolof Earth Sciences and Engineering,Sun Yatsen Universiy Zhuhai 519080,China;Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519080,China)

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,珠海519080 [2]南方海洋科学与工程广东省实验室(珠海),珠海519080

出　　处：《科学通报》2024年第18期2618-2631,共14页Chinese Science Bulletin

基　　金：国家自然科学基金(42330302);国家重点研发计划(2023YFF0803701);南方海洋科学与工程广东省实验室(珠海)项目(SML2023SP206)资助。

摘　　要：华南陆块东部在中生代时期主要受古特提斯和古太平洋两大构造域的影响,发育多期岩浆活动和大规模成矿作用,但两大构造域的转换时间及过程存在较大争议.基性岩是研究软流圈、岩石圈地幔和俯冲板片相互作用的理想对象,本文系统厘定了华南陆块东部中生代基性岩(228~69 Ma)的时空格架及元素-同位素时空演变规律,取得了以下主要认识:(1)侏罗纪和白垩纪基性岩按照岩相学和元素-同位素地球化学特征均可分为OIB、类OIB和“岛弧”/岛弧型三类,它们来源于不同的地幔源区;(2)侏罗纪“岛弧”型基性岩的时空分布和元素-同位素地球化学性质明显有别于晚三叠世基性岩和白垩纪岛弧型基性岩,说明它们并非是与古太平洋板块俯冲相关的岛弧岩浆,其“岛弧”性质很可能是继承了源区的特征;(3)两大构造域转换的起始时间为早侏罗世早期(约200 Ma),完成转换的最终时间为中-晚侏罗世之交(约170 Ma);(4)古太平洋构造域自晚侏罗世以来对华南陆块东部的影响越来越明显,白垩纪时期的板片交代影响范围仅局限于赣江断裂以东地区;(5)白垩纪基性岩主要形成于两个峰期(约125和90 Ma),与古太平洋板块的两期俯冲-回撤作用有关.The eastern South China Block(SCB)was mainly influenced by Paleo-Tethyan and Paleo-Pacific dynamic domains during the Mesozoic,accompanied by intensive magmatism and mineralization.However,the tectonic transition and evolution of these two dynamic domains remain debated.The tectonic transition has significant effects on the tectonic,sedimentary and magmatism activities in the eastern SCB.The mafic igneous rocks are excellent indicators for exploring the interaction among asthenosphere,lithosphere mantle and subducted slab.The spatio-temporal framework of Mesozoic mafic rocks is critical for unravelling the tectonic transition and evolution.Thus,this paper complied the geochronology and geochemistry data of Mesozoic mafic igneous rocks in the eastern SCB,aiming to constrain the tectonic transition and the influence of Paleo-Pacific Plate subduction.The formation ages of the Mesozoic mafic igneous rocks(228-69 Ma)mainly fall into five age-clusters at ca.228-223 Ma,ca.197-169 Ma,ca.168-146 Ma,ca.143-115 Ma,and ca.113-69 Ma.The Triassic mafic igneous rocks in the eastern SCB are enriched in large-ion lithophile elements(LILE)and high-field strength elements(HFSE)with significant Nb-Ta positive anomalies.They have high(87Sr/86Sr)iratios and lowεNd(t)values,deriving from partial melting of an enriched lithosphere mantle and forming in an post-collision setting associated with the Paleo-Tethyan dynamic domain.The Jurassic and Cretaceous mafic igneous rock can be geochemically classified into OIB-,OIB-like-and“arc”/arc-types,originating from different mantle sources.The OIB and OIB-like mafic rocks were derived from asthenosphere and asthenosphere-lithosphere interaction,respectively.The Cretaceous arc mafic rocks were derived from a mantle wedge which was modified by Paleo-Pacific subducted slab-derived melts/fluids.The Cretaceous mafic rocks show geochemical variations from the interior(OIB and OIB-like-types)to coastal provinces(arctype).From the interior to coastal provinces,the Cretaceous mafic igneous rocks ex

关 键 词：中生代基性岩 古太平洋构造域 古特提斯构造域 构造转换 华南陆块 

分 类 号：P548[天文地球—构造地质学] P534.5[天文地球—地质学]