High-Field-Strength Elements in Mafic Volcanics from North China Craton: Implications for Archean-Proterozoic Boundary and Source Composition  

作　　者：Liu Yongsheng Gao Shan Luo Tingchuan Faculty of Earth Sciences, China University of Geosciences, Wuhan 430074 

出　　处：《Journal of Earth Science》1998年第2期17-23,共7页地球科学学刊（英文版）

摘　　要：Archean to Cenozoic mafic volcanic rocks from the North China craton are studied. They show Archean Proterozoic (Ar Pt) boundary and geochemical anomalies in Cenozoic basalts. Proterozoic mafic volcanics are enriched in most of the high field strength elements (HFSE) compared with Archean ones. Nb, Ta and Th show a distinct sequence of incompatibility in Archean and Proterozoic. The Cenozoic basalts are enriched in HFSE and Ni and their REEs are strongly differentiated with positive Eu anomalies ( δ (Eu)=1.14). The Ar Pt boundary could be related to change in oxygen fugacity and requires an increasing importance of enriched mantle source. The geochemistry of Cenozoic basalts implies a mantle source similar to OIB. Residuum from subducting partial melting of old basaltic oceanic crust and continental crust is likely to contribute to the formation of the enriched mantle.Archean to Cenozoic mafic volcanic rocks from the North China craton are studied. They show Archean Proterozoic (Ar Pt) boundary and geochemical anomalies in Cenozoic basalts. Proterozoic mafic volcanics are enriched in most of the high field strength elements (HFSE) compared with Archean ones. Nb, Ta and Th show a distinct sequence of incompatibility in Archean and Proterozoic. The Cenozoic basalts are enriched in HFSE and Ni and their REEs are strongly differentiated with positive Eu anomalies ( δ (Eu)=1.14). The Ar Pt boundary could be related to change in oxygen fugacity and requires an increasing importance of enriched mantle source. The geochemistry of Cenozoic basalts implies a mantle source similar to OIB. Residuum from subducting partial melting of old basaltic oceanic crust and continental crust is likely to contribute to the formation of the enriched mantle.

关 键 词：mafic volcanic rocks high  field  strength element Archean  Proterozoic boundary enriched mantle. 

分 类 号：P594.1[天文地球—地球化学]