厄立特里亚西部新元古代岛弧花岗岩对东非造山带构造演化的指示意义OA北大核心CSTPCD

The East African orogen is a collisional collage belt of East Gondwana and West Gondwana.A deep study of the evolution of the orogenic belt is of great significance for understanding the supercontinent cycles.Zircon LA-ICP MS U-Pb ages and Hf isotopic compositions,whole rock major and trace elements and Sr-Nd isotopic compositions of the Meraf granite within the Augaro,west Eritrea,are reported in this paper to study the petrogenesis and implications for the Neoproterozoic tectonic evolution of the East African orogenic belt.LA-ICPMS zircon U-Pb dating of the Meraf granite yields magmatic crystallization age of(875±6)Ma.The Meraf granite has geochemistry patterns resembling those of Arc-type granite,with high-SiO2,calc-alkaline and peralu-minous,and enriched in LREE and LILE such as Ba,Rb,K,relatively depleted in HREE and HFSE such as Ta,Nb,Ti,with weak Eu negative anomalies(δEu= 0.70-0.91).Combined with the positive εHf(t)(7.7～9.9),low initial 87Sr/86Sr(0.702 00～0.702 73),and remarkable εNd(t)values(4.85～6.06),the Meraf granite is supposed to be the product of partial melting of the mantle wedge triggered by dehydration of the subducting oceanic plate.Together with widespread Neoproterozoic arc-type granites in the East African orogen,the break-up of Super-continent and formation of Mozambique oceanic are believed to predate the 875Ma.