摘要
晚中生代是古太平洋板块俯冲东亚大陆的重要时期,也是华南大陆构造-岩浆活动的重要时期。本文通过东海陆架盆地紧邻海礁隆起ECSs611钻井的渐新统花港组(1626~1638m)砂岩和白垩系(1638~1689m)砂岩碎屑锆石U-Pb同位素和微量元素等研究,获得了~163Ma和~120Ma两期岩浆-变质事件的锆石U-Pb年龄记录。两期岩浆锆石均具有结晶温度低(556~732℃)、流体活动元素U富集(含量82×10-6~3412×10-6)及高场强元素Nb亏损(含量0.6×10-6~13.8×10-6)等特点,它们形成于岩浆弧构造环境。与洋壳锆石相比,两期岩浆锆石元素Y含量(371×10-6~2700×10-6)和U/Yb比值(0.2~6.7)偏低,指示其属于大陆锆石类型。其它碎屑锆石年龄(如2.5~2.4Ga,1.7~1.6Ga,320 Ma和256~207 Ma)与华南大陆主要构造事件一致,初步认为东海海礁隆起应属于华南大陆(华夏地块)东延的部分。如果将海礁-虎皮礁隆起作为晚侏罗世至早白垩世岩浆弧一部分,与东海福州凹陷弧前盆地和西南日本至台湾俯冲增生杂岩等单元联结起来,区域上可构成受古太平洋板块俯冲控制的晚中生代东亚大陆边缘构造轮廓,即岩浆弧→弧前盆地→俯冲增生杂岩。
The Late Mesozoic is an important tectonic period for subduction of the Paleo-Pacific slab beneath East Asia and continental tectonic magmatic activities.Sandstones from the Well ECSs611 closely adjoining the Haijiao Uplift from the East China Sea are investigated in order to trace late Mesozoic magmatic arc by U-Pb isotopic dating of detrital zircons from the Oligocene Huagang Formation(1626~1638 m)and the Cretaceous(1638~1689 m)sandstones.Results show that the detrital zircons from the Huagang Formation and the Cretaceous samples are mainly magmatic zircons with some metamorphic ones that formed in two episodes at^163 Ma and ~120 Ma respectively,registering two late Mesozoic magmaticmetamorphic events.These magmatic zircons from arc-related magmatic source are characterized by lowtemperature(556~732 ℃),enrichment of fluid-mobile U(82×10-6-3412×10-6)and high fieldstrength Nb depletion(0.6×10-6~13.8×10-6).Compared with the oceanic zircons,these magmatic zircons which formed in two episodes of^163 Ma and^120 Ma are characterized by lower Y(371×10-6~2700×10-6)and U/Yb ratio(0.2~6.7).Hence we infer that these magmatic zircons belong to continental zircons.These magmatic zircons are continental rather than oceanic,while other ages from detrital zircons(2.5~2.4 Ga,1.7~1.6 Ga,320 Ma and 256~207 Ma)are consistent with key tectonic events undergone by the South China block.It is inferred that the Haijiao uplift zone belongs to eastward extension of South China.The Haijiao-Hupijiao zone as a magmatic arc,together with units of the Fuzhou forearc basin and SW Japan-Taiwan subduction accretionary complex constitutes an outline of late Mesozoic continental margin of East China Sea,formed by the subduction of the paleo-Pacific slab.
作者
李晓龙
许长海
高顺莉
黄湘通
赵洪
张成晨
LI Xiaolong;XU Changhai;GAO Shunli;HUANG Xiangtong;ZHAO Hong;ZHANG Chengchen(State Key Laboratory of Marine Geology,School of Ocean and Earth Science,Tongji University,Shanghai,200092;CNOOC China Limited-Shanghai,Shanghai,200335)
出处
《地质学报》
EI
CAS
CSCD
北大核心
2020年第2期480-490,共11页
Acta Geologica Sinica
基金
国家自然科学基金项目(批准号:41876045)
国家科技重大专项课题(批准号:2017ZX05005001-005)资助的成果.
关键词
岩浆弧
晚中生代
碎屑锆石
U-Pb年代
东海
magamatic arc
Late Mesozoic
U-Pb geochronology
detrital zircon
East China Sea
作者简介
李晓龙,男,1994年生,硕士研究生在读,主要从事大陆边缘构造演化研究,Email:1632968@tongji.edu.cn;通讯作者:许长海,男,1971年生,教授。从事大陆边缘构造演化,造山带隆升、剥蚀与地形演变研究,Email:xchxch@tongji.edu.cn。
