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东海陆架西部凹陷带古新统砂岩锆石的U-P年龄表明,陆架西部古新世物源以中生代母岩为主,其次为元古代变质岩及少量古生代母岩。东海陆架东部凹陷带渐新统砂岩锆石的U-P年龄表明陆架东部渐新世物源以元古代变质岩为主,其次为中生代母岩及少量太古代变质岩与古生代母岩。陆架西部古新统砂岩锆石的U-P年龄与闽浙隆起带露头及钻孔揭示的基岩一致,而陆架东部渐新统砂岩锆石的U-P年龄比西部老。根据上述砂岩锆石U-P年龄,可以推测古近纪东海陆架盆地发育过程中,东海陆架东部地势较高。单颗粒锆石REE配分模式表明元古代锆石轻稀土(LREE)明显比其他样品高且含量相近,Ce正异常不明显;中生代锆石Ce正异常明显,但同时Eu负异常也很明显,与中生代基岩锆石相似;古生代锆石稀土元素含量偏低,La含量明显超过其他轻稀土元素。根据上述特征可以清晰指示砂岩的母岩类型与年代,推断古新世东海大陆架的基底性质与构造背景。
The U-P ages of the zircons from the Paleocene sandstone in the western sag of the East China Sea continental shelf show that the Paleocene source rocks in the western shelf are dominated by Mesozoic parent rocks, followed by Proterozoic metamorphic rocks and a small amount of Paleozoic parent rocks. The U-P ages of Zircon in the Oligocene sandstones in the Eastern Depression of the East China Sea shelf indicate that the Oligocene source rocks in the eastern shelf are dominated by metamorphic rocks, followed by Mesozoic parent rocks and a small amount of Archean metamorphic rocks and Paleozoic parent rocks. The U-P ages of the Paleocene sandstone in the western shelf are consistent with the bedrock revealed by the outcrops and boreholes in the Fujian-Zhejiang uplift and the U-P ages of the Oligocene sandstone in the eastern shelf are older than those in the west. According to the U-P ages of the zircons from the sandstone, it can be inferred that during the development of the continental shelf in the East China Sea in the Paleogene, the terrain of the eastern shelf of the East China Sea is relatively high. The single grain zircon REE distribution pattern shows that the LREE of Proterozoic zircons is obviously higher and similar to that of other samples, and the positive Ce anomaly is not obvious. The Ce of Mesozoic zircons is anomalous obviously, but the Eu negative anomaly is also obvious. The Mesozoic bedrock zircons are similar. The Paleozoic zircons have lower REE content and La content than other light REEs. Based on the above characteristics, the rock types and ages of sandstone can be clearly indicated, and the basement and tectonic setting of the continental shelf in the East China Sea in the Pliocene can be inferred.