摘要
晚中生代是古太平洋板块俯冲东亚陆缘的重要时期,也是华南大陆岩浆活动的重要时期。本文选用东海陆架丽水凹陷FZ211井紧邻中生代花岗岩基底的石门谭组(2031~2097m)和明月峰组(1755~1806m)的砂岩样品,开展碎屑锆石U-Pb同位素和微量元素等分析,获得了侏罗纪(180~160Ma)和白垩纪(140~80Ma)两期主要的岩浆事件记录,以120~80Ma年龄组分更为发育。两期岩浆锆石均具有结晶温度低(605~792℃)、流体活动元素U、Th和LREE富集以及高场强元素Nb、Ta、Ti和HREE亏损特点,它们形成于典型的岩浆弧构造环境,岩浆中侏罗纪俯冲物质的加入明显优于白垩纪。与洋壳锆石相比,两期岩浆锆石U/Yb值(0.1~5.1)与大陆锆石类型一致,白垩纪岩浆锆石呈现向洋壳锆石过渡的趋势。东海渔山隆起应是晚中生代大陆岩浆弧的重要组成部分,120~80Ma是俯冲和岩浆活动的强烈时期,东亚陆缘从侏罗纪到白垩纪显现出古太平洋板块俯冲回滚的特点。如果将渔山隆起岩浆弧与福州凹陷弧前盆地和SW日本到台湾的俯冲杂岩联结起来,区域上可构成晚中生代东亚陆缘汇聚的构造轮廓,即岩浆弧-弧前盆地-俯冲增生杂岩。
The Late Mesozoic was an important period in the subduction of the Paleo-Pacific plate and the development of the East Asian continental margin accompanied by intense magmatic activity in the South China block.In this paper,the sandstone samples from the Shimentan Formation(2031~2097m)and the Mingyuefeng Formation(1755~1806m),closely adjoining the Mesozoic granite basement,were selected from the well FZ211in Lishui sag,East China Sea,for analysis of detrital zircon U-Pb isotopes and trace elements.We obtained the result of two major magmatic events that activated in the Jurassic(180~160 Ma)and in the Cretaceous(140~80Ma),respectively,within which the age range of 120~80Ma was a major period.The dated detrital zircons from the two magmatic episodes are characterized by low temperature(605~792℃),fluid-mobile elements U,Th,and LREE enrichment,and depletion in high field-strength elements Nb,Ta,Ti,and HREE.They were formed in a typical magmatic arc environment.Compared with oceanic-type zircon,the U/Yb ratios(0.1~5.1)of dated igneous zircons fall in the range of continental-type zircon,but with a transitional trend towards the type of oceanic zircon in the Cretaceous.The Yushan uplift from the East China Sea,as a sediment source for the dated samples,should be an important part of the Late Mesozoic magmatic arc,with strong subduction and magmatic activity in the period of 120~80Ma.The Yushan magmatic arc,if connected with units of the Fuzhou forearc basin and SW Japan-Taiwan accretionary complexes,constitutes an architecture of Late Mesozoic continental margin of East China Sea,that was controlled by the subduction of Paleo-Pacific slab rollback.
作者
斯琴
许长海
高顺莉
SI Qin;XU Changhai;GAO Shunli(State Key Laboratory of Marine Geology,School of Ocean and Earth Science,Tongji University,Shanghai 200092,China;CNOOC China Limited-Shanghai,Shanghai 200335,China)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2021年第6期1743-1753,共11页
Acta Geologica Sinica
基金
国家自然科学基金项目(编号41876045)
国家科技重大专项课题(编号2017ZX05005001-005)联合资助的成果。
关键词
碎屑锆石
岩浆弧
晚中生代
东亚汇聚
东海
detrital zircon
magmatic arc
East Asian convergence
Late Mesozoic
East China Sea
