Sm-Nd Isotopic Signatures and Significance of the Precambrian-Cambrian Seawater in China

【摘要】 <正> Sm-Nd isotopic determination on small shelly fossils and collophanites collected from 3Precambrian-Cambrian boundary sections,namely Meishucun of Jinning in Yunnan,Maidiping of Emei inSichuan and Wushi of Kalpin in Xinjiang,shows that the seawater masses of these three remotely separatedareas were co-oceanic in the Precambrian-Cambrian transitional period,with a common seawater ε_Nd（T） val-ue of -6.6±0.5.The ε_Nd（T） value of the China’s seawater ranges from -5.7 to-6.6 during the periodfrom 610 Ma B.P.to 500 Ma B.P.The research suggests that there could be an "Asiaustralian Ocean" be-sides the Panthalassa Ocean and the Iapetus Ocean at that time,and the China’s seawater possibly belongedto the Asiaustralian Ocean.The Sm-Nd model age of the determined samples is about 1.8 Ga,which reflectsthe mean age of the continental source areas around the China’s seawater.更多还原

【Abstract】 Sm-Nd isotopic determination on small shelly fossils and collophanites collected from 3 Precambrian-Cambrian boundary sections,namely Meishucun of Jinning in Yunnan,Maidiping of Emei in Sichuan and Wushi of Kalpin in Xinjiang,shows that the seawater masses of these three remotely separated areas were co-oceanic in the Precambrian-Cambrian transitional period,with a common seawater ε_Nd（T） val- ue of -6.6±0.5.The ε_Nd（T） value of the China’s seawater ranges from -5.7 to-6.6 during the period from 610 Ma B.P.to 500 Ma B.P.The research suggests that there could be an "Asiaustralian Ocean" be- sides the Panthalassa Ocean and the Iapetus Ocean at that time,and the China’s seawater possibly belonged to the Asiaustralian Ocean.The Sm-Nd model age of the determined samples is about 1.8 Ga,which reflects the mean age of the continental source areas around the China’s seawater.更多还原