东海陆架到南海北部晚中生代东亚汇聚边缘演变的岩浆弧记录

This project, aimed at "where are located the typical Late-Mesozoic arc-subduction-related igneous rocks along the continental margin of South China", is designed regionally mainly from the continental shelf areas more close to the subduction zone from SW East China Sea to N South China Sea combined with Fujian few coastal area to focus on studies of Pre-Cenozoic igneous rocks from 95 boreholes that already collected on the basis of former NSFC No.41272218 and others. This project comes to stress both integrated and comparative studies of igneous rocks from the different areas on petrology, Sr–Nd bulk-rock isotopes, zircon U–Pb geochronology, O-Hf isotopes, Ti-temperature, and other geochemical analyses in order to obtain key records of formation and evolution of Late-Mesozoic magmatic arc in these areas previously lack of studies on Mesozoic igneous rocks. The results from this project will no doubt add key constraints on evolution of Late Mesozoic convergent continental margin in East Asia driven by paleo-Pacific slab subduction, together provide unusual information for understanding of Mesozoic basin prototypes and resource potentials from East to South China Seas.

针对"华南陆缘晚中生代典型的俯冲岩浆弧型岩浆岩残留在哪里？"这一科学问题，本项目拟选择邻近俯冲带的东海陆架到南海北部这一海陆结合部，在前一个基金项目(No.41272218)等工作基础上，依托课题组现有约95口井钻遇岩石样品(前新生代)并辅以福建沿海部分样品，开展以岩浆岩为主的岩石学、锆石U-Pb年代学、全岩Sr-Nd和锆石O-Hf同位素及其它地球化学等对比研究分析，以取得这一岩浆岩薄弱研究区晚中生代岩浆弧形成演变的关键记录，形成古太平洋板块俯冲和东亚晚中生代大陆边缘汇聚体制的关键约束，为深化我国东南海域中生界盆地原型及油气资源潜力认识提供重要依据。

针对“华南陆缘晚中生代典型岩浆弧在哪里？”这一热点问题，项目选择邻近俯冲带的东海陆架到南海北部这一海陆结合部，围绕构造岩浆事件演变主线，开展构造学、岩石学和地球化学综合研究，以取得我国东南海域晚中生代岩浆弧形成演变的关键记录，同时综合华南陆内构造和婆罗洲构造岩浆研究，取得了Izanagi板块俯冲和东亚大陆活动大陆边缘的关键约束和认识：1）认为东海陆架到南海北部基底形成于2.5Ga和1.85Ga，先后经历了晋宁期碰撞造山及大陆裂解、加里东期和印支期陆内造山的构造改造，它们应是华夏地块向东南延伸部分，没有发现它们属于外来地块的证据；2）认为东海陆架到南海北部发育不同于华南大陆板内岩浆作用的晚中生代岩浆弧，重建了晚中生代华南大陆边缘“沟-弧-板内”结构，初步提出不同于安第斯型陆缘的华南活动大陆边缘类型和地球动力学控制模式；3）认为晚中生代是四川东部到雪峰山构造带重要形成时期，构造变形和抬升作用强烈且自东向西构造传递，这种构造传递与Izanagi俯冲东亚及陆内响应关系密切；4）综合分析基底、岩浆弧和区域地质特点，提出婆罗洲北部Izanagi和东南部中特提斯两大构造域的区域俯冲结构和交汇演变模式，初步认为SW婆罗洲属于巽他大陆的延伸部分。项目研究成果，对于深化认识华南晚中生代大陆边缘构造体制、近海中生界残留盆地和古潜山盆地油气勘探潜力，具有重要的科学意义和应用价值。