摘要
琼东南盆地中生代火成岩潜山是海域油气勘探的热点领域,但由于缺少系统的年代学和地球化学分析,有关潜山基岩的岩石成因与动力学背景仍不清楚,制约了潜山油气藏的进一步勘探。本项研究以钻井揭露的辉绿岩为研究对象,开展岩石学、年代学、地球化学和Lu-Hf同位素研究,探讨其岩石成因与动力学背景。LA-ICP-MS锆石U-Pb年代学揭示辉绿岩结晶年龄为(236±3)Ma,形成于晚三叠世。辉绿岩中SiO 2(47.96%~49.97%)和Al 2O 3(13.16%~13.68%)的质量分数较低,MgO的质量分数(6.02%~7.49%)和Mg^(#)值(58~61)较高。岩石具有右倾的稀土配分模式及正Eu异常特征,且样品富集大离子亲石元素,亏损高场强元素。岩石具有富集的锆石Hf同位素组成(εHf(t)=-9.08~-4.70)。岩石成因分析表明,辉绿岩起源于富集地幔熔融,且源区经历了早期俯冲沉积物来源的含水熔体的交代改造。本项研究揭示,琼东南盆地晚三叠世辉绿岩形成于碰撞后伸展环境,属于古特提斯造山旋回的产物。
The buried hills containing Mesozoic igneous rocks in the Qiongdongnan Basin are a major site for offshore oil and gas exploration.However,owing to a lack of systematic chronology and geochemical research,the petrogenesis and tectonic setting of the basement rocks remain unclear,hindering further exploration of oil and gas reservoirs in these buried hills.Here,we comprehensively investigate the petrology,zircon geochronology,whole-rock geochemistry,and zircon Lu-Hf isotopes of diabase collected by drilling in the Qiongdongnan Basin to determine its petrogenesis and tectonic setting.The results of LA-ICP-MS zircon U-Pb geochronology reveals a crystallization age of(236±3)Ma for the diabase,indicating that it formation during the Late Triassic.The diabases have low contents of SiO 2(47.96%~49.97%)and Al 2O 3(13.16%~13.68%),but are enriched in MgO(6.02%~7.49%)and Mg^(#)(58~61).The sampled rocks exhibit right-sloping rare earth elements pattern and positive Eu anomalies,and are enrich in large ion lithophile elements and depletion in high field strength elements.They are also enrich in zircon Hf isotopes(εHf(t)=-9.08~-4.70).The results of petrogenesis analysis indicates that the diabases had originated from the melting of enriched mantle which was metasomatized by early subducted sediments-derived aqueous melts.The results of this study reveals that diabases in the Qiongdongnan Basin formed in a post-collision extension setting,and are products of the Paleo-Tethyan orogeny.
作者
周虎
付于真
胡潜伟
侯明才
陈安清
曹海洋
熊富浩
楚志强
ZHOU Hu;FU Yuzhen;HU Qianwei;HOU Mingcai;CHEN Anqing;CAO Haiyang;XIONG Fuhao;CHU Zhiqiang(College of Earth and Planetary Science,Chengdu University of Technology,Chengdu 610059,China;State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu University of Technology,Chengdu 610059,China;Hainan branch of China National Off shore Oil Limited Corporation,Haikou 570100,China)
出处
《成都理工大学学报（自然科学版）》
CAS
CSCD
北大核心
2024年第4期543-560,共18页
Journal of Chengdu University of Technology: Science & Technology Edition
基金
国家自然科学基金项目(41602049)
中海石油(中国)有限公司海南分公司科技项目(CCL2021HNFN0242,CCL2021HNFN0248)。
关键词
琼东南盆地
潜山
年代学
地球化学
大地构造
Qiongdongnan Basin
buried hills
chronology
geochemistry
tectonic
