福州凹陷中生代沉积源区示踪：剖析东海陆架区域基底属性

东海陆架区基底是华南大陆向海域的延伸还是晚侏罗世-早白垩世期间的外来块体一直存在争议，直接影响到国内外学者对西太平洋中生代以来构造演化的认识。已有研究表明，碎屑锆石U-Pb定年及Hf同位素物源分析可为源区地壳演化以及是否发生块体拼贴提供直接证据。东海福州凹陷钻井揭示了华南近海海域最为完整的J1-K2沉积序列，区内物源演化是分析东海基底归属争议的最佳对象。本研究拟选取研究区两口中生代地层建组剖面井进行源区示踪分析，通过对各层位的系列样品进行碎屑锆石U-Pb年代学及Hf同位素分析，并与华夏块体已有数据进行详细对比，厘定其碎屑物质来源。在此基础上，结合同时期华南沿海及海域沉积古地理演化，确定该时期是否发生块体的拼贴，并针对来自东海基底的碎屑锆石分析其揭示的陆壳增生情况，探讨东海基底与华南基底在地质历史中的关系。本课题将为判别东海陆架是否为外来块体以及探索其基底属性提供关键证据。

Whether the basement of continental shelf beneath the East China Sea (CSECS) is part of Cathaysia Block or is an exotic block during J3-K1 has remained controversial for decades, which directly affects the understanding of the tectonic evolution of the Western Pacific since the Mesozoic. Recent researches have demonstrated that the detrital zircon U-Pb age and Hf isotope provenance analysis can provide an effective indicator for probing the generation and reworking of continental crust and the occurrence of continental collision. Thus, the Fuzhou Sag, which is observed to have the most complete Lower Jurassic-Upper Cretaceous sedimentary sequences in the offshore area of South China by exploration wells, is an ideal place to solve the problem by provenance analysis. This research attempts to use a series of samples from two wells, which have been established the Mesozoic formation, to investigate the provenance of Mesozoic strata in this area by detrital zircon U-Pb chronology and Hf isotopic, as well as comparison with existing data in Cathaysia block. Furthermore, the exotic origin model can also be determined combining with the contemporary paleogeographic environment evolution of inland and offshore areas in South China. Based on the above analysis, the continental crust accretion can be deciphered by detrital zircons sourced from CSECS, which leads to better understanding of the relationship between the CSECS and the Cathaysia block. This study will provide key evidence to clarify the exotic origin model and explore the basement properties beneath the East China Sea.