东海丽水凹陷晚古生代碎屑锆石的发现及其意义

Discovery of Late Paleozoic Detrital Zircons in Lishui Sag, East China Sea, and Its Significance

摘要:

通过对东海新生代陆架盆地丽水凹陷N6井月桂峰组和灵峰组下段地层碎屑锆石UPb定年，发现月桂峰组碎屑锆石主要为岩浆锆石，包括140—90 Ma和190—170 Ma两个年龄组分，并有零星的大于400 Ma的变质锆石；向上至灵峰组下段碎屑锆石中除上述锆石年龄组分外，新出现280—260 Ma的变质锆石组分，说明除140—90 Ma及190—170 Ma岩浆岩物源外，随着物源区持续剥蚀，至灵峰组下段物源区明显加入了280—260 Ma变质岩.这一与二叠纪相关的变质碎屑锆石和变质作用，可能与晚古生代古太平洋板块汇聚华南大陆有关.

Abstract:

Detrital zircons were selected for UPb isotopic dating from Yueguifeng Formation (YF) and Lower Lingfeng Formation(LF) of the well N6 in Lishui Sag, East China Sea Shelf Basin. The results show that detrital zircons in YF are mainly magmatic zircons formed between 14090 Ma and 190170 Ma, while others are minor and mostly metamorphic zircons, older than 400 Ma in age. Apart from the above age populations, metamorphic zircons formed in 280260 Ma appeare in LF. This indicates that the provenance of YF is mainly magmatic rocks of 14090 Ma and 190170 Ma. With sustained erosion of the source area, metamorphic rocks that formed in 280260 Ma are significantly exposed and added. These permian detrital zircons with metamorphism may be related to the convergence between paleo Pacific plate and South China.