珠江口盆地晚侏罗世中基性火山岩的岩石成因与构造意义:来自年代学和地球化学的约束  

Petrogenesis and tectonic significance of the Late Jurassic intermediate-mafic volcanic rocks in the Zhujiangkou basin:Constraints from geochronology and geochemistry

作　　者：刘杰 侯明才[2,3] 王菲 牛胜利 梁杰 熊富浩 陈安清[2,3] 钟灵[3] 冷杰 LIU Jie;HOU Mingcai;WANG Fei;NIU Shengli;LIANG Jie;XIONG Fuhao;CHEN Anqing;ZHONG Ling;LENG Jie(CNOOC Ltd-Shenzhen,Shenzhen,Guangdong 518054,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,CDUT,Chengdu,Sichuan 610059,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu,Sichuan 610059,China;College of Earth Science,Chengdu University of Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]中海石油(中国)有限公司深圳分公司,广东深圳518054 [2]成都理工大学油气藏地质及开发工程国家重点实验室,四川成都610059 [3]成都理工大学沉积地质研究院,四川成都610059 [4]成都理工大学地球科学学院,四川成都610059

出　　处：《地质学报》2023年第2期364-375,共12页Acta Geologica Sinica

基　　金：中海石油(中国)有限公司深圳分公司科技项目(编号CCL2020SZPS0304)资助的成果。

摘　　要：位于南海北部陆缘的珠江口盆地发育中生代岩浆岩,记录了古太平洋板片俯冲消亡的动力学过程。本项研究以钻井揭露的晚侏罗世火山岩为研究对象,开展系统的岩石学、岩相学、年代学和地球化学研究,探讨其成因机制和动力学背景。岩石学及地球化学分析显示,这套火山岩由玄武岩、玄武安山岩、安山岩和粗面安山岩组成。LA-ICP-MS锆石U-Pb年代学分析表明,玄武安山岩的结晶年龄为154.0±3.2 Ma。岩石的SiO2含量为49.54%~58.22%,K2O含量为0.71%~3.00%,MgO含量为5.29%~11.05%,Mg#值介于52~66之间,属于高钾钙碱性系列中基性火山岩。岩石的轻重稀土元素分馏明显,(La/Yb)N比值为5.00~6.93,且具有轻微的铕负异常,δEu值为0.73~1.04。样品显著富集大离子亲石元素Rb、Ba、Th和U等,相对亏损高场强元素Nb、Ta、Ti和P等。岩石成因分析表明,晚侏罗世中基性火山岩主要起源于受俯冲板片流体交代的富集岩石圈地幔熔融,且岩浆经历了辉石、角闪石等矿物的分离结晶。综合区域资料,本文认为珠江口盆地于晚侏罗世时期处于古太平洋板片向华南板块持续俯冲的陆缘弧环境。Mesozoic igneous rocks developed in the Zhujiangkou basin on the northern margin of the South China Sea record the dynamic processes of subduction and closure of the Paleo-Pacific slab.We present a systematic study of the petrology,petrography,chronology and geochemistry of the late Jurassic volcanic rocks exposed by drilling in the Zhujiangkou basin,to explore their petrogenesis and dynamic setting.Petrology and geochemical analysis show that the studied volcanic rocks are composed of basalt,basalt andesite,andesite and trachyandesite.LA-ICP-MS zircon U-Pb geochronology study shows that the crystallization age of basalt andesite is 154.0±3.2 Ma.The studied rocks have SiO2content of 49.54%~58.22%,K2O content of 0.71~3.00%,MgO content of 5.29%~11.05%,and Mg#value of 52~66,belonging to the high potassium calc-alkaline series.The rocks exhibit enrichment in light REE with the(La/Yb)Nratio of 5.00~6.93,and show slight negative Eu anomaly withδEu value of 0.73~1.04.These samples are significantly enriched in large-ion lithophile elements such as Rb,Ba,Th and U,and depleted in high field strength elements such as Nb,Ta,Ti and P.Petrogenesis analysis shows that the Late Jurassic mafic-intermediate volcanic rocks mainly originated from the melting of the enriched lithospheric mantle metasomatized by subducted slab-related fluids,and the parental magma experienced fractional crystallization of minerals such as pyroxene and amphibole.Combined with regional data,this paper proposes that the Zhujiangkou basin was in a continental marginal arc environment related to the Paleo-Pacific slab subducting beneath the South China block during the Late Jurassic.

关 键 词：珠江口盆地 晚侏罗世 火山岩 年代学 地球化学 

分 类 号：P588.14[天文地球—岩石学] P534.52[天文地球—地质学]