Magmatic-tectonic response of the South China Craton to the Paleo-Pacific subduction during the Triassic:a new viewpoint based on Well NK-1  

作　　者：Chan WANG Hao LIU Gang LI Zhen SUN Tingting GONG Li MIAO Xiaowei ZHU Yunying ZHANG Weihai XU Wen YAN 

机构地区：[1]Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,China [2]Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou),Guangzhou 511458,China [3]Key Laboratory of Tectonic Controlled Mineralization and Oil Reservoir of Ministry of Natural Resources,Chengdu University of Technology,Chengdu 610059,China [4]School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083,China [5]College of Earth Science,Chengdu University of Technology,Chengdu 610059,China [6]University of Chinese Academy of Sciences,Beijing 100049,China

出　　处：《Journal of Oceanology and Limnology》2024年第1期58-89,共32页海洋湖沼学报（英文）

基　　金：the National Natural Science Foundation of China(No.42206073);the National Key R&D Program of China(No.2021YFC3100600);the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515110782);the China Post-doctoral Science Foundation(No.2021M703296);the Open Fund of the Key Laboratory of Tectonic Controlled Mineralization and Oil Reservoir of the Ministry of Natural Resources(No.gzck202101);the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(No.GML2019ZD0206);the K.C.Wong Education Foundation(No.GJTD-2018-13);。

摘　　要：The Nansha Block(NB)is one of the blocks separated from the southern margin of the South China Craton(SCC)by the western Pacific subduction,which contains rich information of geodynamic and tectonic transformation.To reveal the essence of western Paleo-Pacific subduction during the Triassic period,Well NK-1 in this block was selected for petrographic study,and published research data from other cooperative teams were compared.A double-cycle pattern of basic to neutral magmatic volcanism was established,and 36 lithological rhythmic layers and representative cryptoexplosive breccia facies and welded tuff bands were identified.Combined with a reanalysis of published geochronological data,geochemical elements,and isotope geochemistry,we found that the rock assemblages could be divided into an intermediate-acid dacite(DA)series(SiO_(2)>65%)and basaltic(BA)series(Co<40μg/g),which was formed during the early Late Triassic((218.6±3.2)–(217.9±3.5)Ma).BA exhibits obvious calc-alkaline island-arc magmatic properties:(^(87)Sr/^(86)Sr)_i ratio ranging 0.70377–0.71118(average:0.70645),^(147)Sm/^(144)Nd ratio ranging 0.119–0.193(average:0.168),and chondrite-normalized rare earth element(REE)curves being flat,while DA exhibits remarkable characteristics of subducted island-arc andesitic magma:(^(87)Sr/^(86)Sr)_i ratio(0.70939–0.71129;average:0.71035),εNd(t)value(-6.2–-4.8;average:-5.6)andε_(Hf)(t)value(-2.9–-1.7,average:-2.2)show obvious crust-mantle mixing characteristics.BA and DA reveal typical characteristics of island-arc magma systems and typeⅡenriched mantle(EM-Ⅱ)magma.BA magma was likely resulted from the process whereby the continental crust frontal accretionary wedge was driven by the Paleo-Pacific slab subduction into the deep and began to melt,resulting in a large amount of melt(fluid)joined the asthenosphere on the side of the continental margin.In contrast,DA magma was likely resulted from the process whereby the plate front was forced to bend with increasing subduction distance,which triggered

关 键 词：Paleo-Pacific tectonic domain tectonic evolution rift volcanic rock Nansha Block South China Craton 

分 类 号：P534.51[天文地球—古生物学与地层学] P588.11[天文地球—地质学]