早三叠世-晚白垩世古太平洋俯冲:沙巴的弧前岩浆记录  

Early Triassic-Late Cretaceous Paleo-Pacific subduction zone along the East Asia continental margin:Fore-arc igneous records in Sabah of NE Borneo

作　　者：王岳军 吴赛男 钱鑫 Junaidi Bin Asis 王洋 张玉芝 冯庆来[3] 王伟涛 张培震 Yuejun Wang;Sainan Wu;Xin Qian;Junaidi Bin Asis;Yang Wang;Yuzhi Zhang;Qinglai Feng;Weitao Wang;Peizhen Zhang(Guangdong Key Lab of Geodynamics and Geohazards,School of Earth Sciences and Engineering,Sun Yat-sen University,Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai),Zhuhai 519082,China;Faculty of Science and Natural Resources,University Malaysia Sabah,Sabah 88400,Malaysia;State Key Laboratory of Geological Processes and Mineral Resources,School of Earth Sciences,China University of Geosciences,Wuhan 430074,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,南方海洋科学与工程广东省实验室(珠海),珠海519082 [2]Faculty of Science and Natural Resources,University Malaysia Sabah,Sabah 88400,Malaysia [3]中国地质大学(武汉)地球科学学院,地质过程与矿产资源国家重点实验室,武汉430074

出　　处：《科学通报》2023年第8期954-971,共18页Chinese Science Bulletin

基　　金：国家自然科学基金(41830211,U1701641);广东省基础与应用基础研究项目(2018B030312007,2016ZT06N331)资助。

摘　　要：厘定东亚大陆边缘中生代弧前岩浆记录以限定其俯冲边界及其时序,是解码古太平洋俯冲体系的关键.基于婆罗洲所处特殊大地构造位置且其具有弧前指示意义的基性-超基性岩石报道较少,本文选择菲律宾巴拉望构造带南延之婆罗洲沙巴地区开展了系统研究.对昔加麦火成岩、古达、特鲁比和达弗尔湾蛇绿岩基性岩及相关岩石的全岩Ar-Ar和锆石U-Pb年代学、全岩元素和Sr-Nd-Pb同位素地球化学的研究表明:沙巴基底发育有前三叠系岩石,构造上亲缘于华夏陆块或地处巽他古陆东缘.原定义为“沙巴非蛇绿岩的昔加麦基底岩石”的安山岩和英云闪长岩等形成于251~179 Ma,具埃达克质岩石地球化学属性,87Sr/86Sr(i)=0.70285~0.70307,εNd(t)=+6.5~+7.7,具太平洋洋中脊玄武岩(Mid-Ocean Ridge Basalt,MORB)型Pb同位素组成,源自俯冲板片派生组分交代的地幔源区,是古太平洋俯冲体系的重要组成部分.限定出沙巴地区蛇绿岩的形成时代介于早-中侏罗世至晚白垩世(约185~85 Ma),其中特鲁比蛇绿岩可能较早发育(约185~140 Ma)、古达蛇绿岩主体形成于早白垩世(约135~112 Ma)、而达弗尔湾蛇绿岩形成持续至晚白垩世(约85 Ma).沙巴蛇绿岩中镁质岩石发育具相似Sr-Nd-Pb同位素组成的MORB型、高铌和富铌基性岩,其87Sr/86Sr(i)=0.70291~0.70567,εNd(t)=+6.6~+10.2,(206Pb/204Pb)i=17.91~19.00、(207Pb/204Pb)i=15.43~15.58和(208Pb/204Pb)i=37.61~38.47,其源区受板片派生熔体的交代改造,形成于古太平洋俯冲弧前背景.该研究限定出东亚大陆边缘的古太平洋西向俯冲至少自早三叠世(约251 Ma)即已启动、并持续至晚白垩世(约85 Ma),具长寿命(>150 Ma)“多阶段幕式进撤”的安第斯型俯冲特征,其白垩纪俯冲前锋位于现今中国台湾东部、菲律宾西部,经沙巴、延入古晋带、甚至帕朗卡拉亚一线.该地区构造格局直至晚白垩世末期-新生代早期才转换为现今西太�East Asia is composed of discrete continental fragments derived from the northern margin of East Gondwana since the Paleozoic.Along its eastern margin,a giant Mesozoic arc igneous zone develops,which extends from Coastal South China into SE Vietnam and Peninsular Malaysia through the northern South China Sea,and then into West Borneo.Identification of Mesozoic fore-arc magmatism along the East Asian continental margin is a key to decoding the Paleo-Pacific supra-subduction system.However,the mafic-ultramafic rocks with the indicative of a fore-arc tectonic setting are poorly documented so far.This paper focuses on the Sabah tectonic zone of NE Borneo that is tectonically proposed as either the southern extension of the Palawan mélange zone or the eastern extension of the Sarawak Kuching tectonic zone.We present zircon U-Pb geochronology and Lu-Hf isotopes,as well as whole-rock Ar-Ar ages,and elemental and Sr-Nd-Pb isotopic data for the igneous rocks in Sabah.The igneous rocks are collected from(1)the previously-defined Segama non-ophiolite basement and(2)the Kudat,Telupid and Darvel Bay ophiolite sequences of the Sabah ophiolite basement,in order to determine the“where,when and what”of the Paleo-Pacific arc-trench gap in the East Asia continental margin.Our data show that the Sabah basement might be formed at pre-Triassic in age and has a tectonic affinity to the Cathaysia of the South China Block.The Sabah ophiolite basement might form between the Early-Middle Jurassic and Late Cretaceous period(~185–85 Ma),the Telupid,Kudat and Darvel Bay ophiolite sequences of which mainly generate at~185–140,~135–112,and~135–85 Ma,respectively.The mafic rocks from the Telupid,Kudat and Darvel Bay ophiolite sequences coexisted with the radiolarian cherts and deep-sea turbidities,and are geochemically classified as the MORB-like,high-Nb and Nb-enriched mafic rocks with similar Sr-Nd-Pb isotopic compositions.Their 87Sr/86Sr(i)andεNd(t)range from 0.70323 to 0.70460 and+7.3 to+10.2,respectively.(206Pb/204Pb)i=17.91�

关 键 词：东亚活动大陆边缘 早三叠世-晚白垩世 古太平洋西向俯冲 弧前岩浆作用 沙巴地区蛇绿岩 昔加麦火成岩 

分 类 号：P534.5[天文地球—古生物学与地层学] P542[天文地球—地质学] P588.11