U-P DATING OF ZIRCONS FROM CENOZOIC SANDSTONE: CONSTRAIN ON THE GEODYNAMIC SETTING OF EAST CHINA SEA SHELF BASIN

The U-P dating data of zircon from Paleocene sandstones in the west of East China Sea shelf indicate that most zircon grains are of Mesozoic origin, and then are Proterozoic, including sporadic Paleozoic ones. The U-P dating data of zircons from Oligocene sandstones in the east of East China Sea shelf indicate that most zircon grains are Proterozoic, and then are Mesozoic, including sporadic Archean and Paleozoic ones. The dating result indicates that the basement is different between the west and the east of East China Sea shelf basin. The western basement is consistent with the outcrop data in Fujian-Zhejiang offshore area. The U-P dating data of zircons imply that topography was low in the west and high in the east of East China Sea shelf during the development of Eogene basin. Chondrite-normalized REE patterns of the individual zircons determined by ICPMS show that the Proterozoic zircons have high content of LREE and invisible Ce anomalies, whereas Mesozoic zircons have large positive Ce and small negative Eu anomalies, and Paleozoic zircons are characterized by low content of LREE in which La is higher in content than other LREE elements. The LAM-ICPMS data give chronological evidence to us to previously identify basement rocks and to probe into tectonic property of the shelf of East China Sea.