The Augaro Arc-type Granite in the Nubia Shield, Western Eritrea: Petrogenesis and Implications for Neoproterozoic Geodynamic Evolution of the East African Orogen

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 peraluminous, 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 ε_Hf (t) (7.7~9.9), low initial ⁸⁷Sr/⁸⁶Sr (0.70200~0.70273), and remarkable ε_Nd(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 Supercontinent and formation of Mozambique oceanic are believed to predate the 875Ma.