Petrology and geochemistry of the Gore-Gambella plutonic rocks: implications for magma genesis and the tectonic setting of the Pan-African Orogenic Belt of western Ethiopia

摘要: Abstract Major and trace element data for granitoid rocks from the Gore-Gambella Precambrian terranes of western Ethiopia have been used to infer their petrogenetic history tectonic environment in which magmas were emplaced. The plutons are found lithotectonic domains Birbir, Baro Geba, emplaced during interval between 830 540 Ma. Geochemical show that Neoproterozoic, pre- syn-kinematic metaplutonic Birbir domain predominantly calc-alkaline with minor low K trondhjemitic granodiorites tonalites. Some granitoids, occurring as sheets or lenticular bodies within high-grade metamorphic domain, peraluminous a wide range incompatible elements such Y Zr. post-kinematic enriched relative older intrusives, suggesting shoshonitic petrochemical affinity. Petrological geochemical bulk represent mantle-derived arc-tholeiitic magmas. variations suggest multistage, probably polybaric evolution these intrusions. lenses petrological characteristics genesis by crustal melting. late- related melting continental crust, followed fractional crystallisation AFC. Overall, plutonic activity reflects geotectonic region through time. compositionally akin those generated subduction modern magmatic arcs; they belong part series interpreted an intraoceanic island-arc environment. occurrence greywacke turbidites rare carbonates submarine deposition supports this hypothesis. intrusions possess signatures imply role both subduction-related intraplate components.