东海陆架盆地椒江凹陷锆石U-Pb定年及意义

为确定东海陆架盆地椒江凹陷前新生代沉积基底的年龄,并对凹陷内断陷期的沉积物源进行示踪研究,选取了椒江凹陷内典型钻孔中的岩屑样品进行锆石U-Pb定年分析测试,并和已有研究成果进行了对比研究。椒江凹陷前新生代基底以岩浆岩为主,碎屑锆石年龄分布特征复杂,主峰值年龄为227 Ma,主要形成于印支晚期,形成环境属于大洋岛弧环境,和丽水东次凹及雁荡低凸起等已有岩浆记录具有一致性;断陷末期古新统明月峰组碎屑锆石具典型岩浆岩特征,其锆石主峰年龄集中在140~90 Ma,其形成环境属于大陆边缘环境。椒江凹陷古新世物源较为单一,与丽水东次凹具有较大可对比性,东部的雁荡低凸起为其古新世断陷期持续提供物源供应。

Zircon U-Pb dating and its significance in Jiaojiang Sag,East China Sea Basin

Using zircon U-Pb dating as the main analysis method, the age of the pre-Cenozoic sedimentary basement was determined and the sediment source in the sag during the fault depression was traced in the Jiaojiang Sag, East China Sea Shelf Basin. The pre-Cenozoic basement of Jiaojiang Sag is dominated by magmatic rocks. The age distribution of detrital zircons is complex, with the main peak age of 227 Ma, mainly formed in the late Indosinian period. The formation environment belongs to the oceanic island arc environment, which is consistent with the existing magmatic records of Lishui East Sub-Sag and Yushandang Low Uplift. The clastic zircons of the Paleocene Mingyuefeng Formation have typical magmatic characteristics, with the main zircon peak ages ranging from 140 Ma to 90 Ma. The formation environment belongs to a continental margin environment. The Paleocene provenance of Jiaojiang Sag is relatively single, which is comparable to Lishui Eastern Sub-Sag. The Yandang Low Uplift in the east of Jiaojiang Sag provides a continuous provenance supply during the Paleocene fault depression.