High-Field-Strength Elements in Mafic Volcanics from North China Craton: Implications for Archean-Proterozoic Boundary and Source Composition |
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Authors: | Liu Yongsheng Gao Shan Luo Tingchuan |
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Abstract: | 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. |
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Keywords: | mafic volcanic rocks high-field-strength element Archean-Proterozoic boundary enriched mantle |
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