Petrology, geochemistry and Sm-Nd systematics of the Paleoproterozoic Itaguara retroeclogite from Sao Francisco/Congo Craton: One of the oldest records of the modern-style plate tectonics

Paleoproterozoic retrogressed eclogite (retroeclogite) occurs in the Itaguara Sequence included in the suture zone formed by collision between the Archean Divinopolis and Campo Belo/Bonfim Complexes in the southern Sao Francisco Craton, which represents the South American counterpart of the African Congo Cra ton. The Itaguara retroeclogite contains scarce omphacite and phengite but abundant garnet porphyroblasts embedded in a finegrained, amphibole, biotite and quartz-bearing matrix. The 2.20 +/- 0.05 Ga edogitization event (garnet and whole rock Sm-Nd isochronic age) of the E-MORB protolith (T-DM similar to 2.47 Ga) is recorded by omphad te formation during high-pressure prograde stage in amphibole edogite fades due to similar to 70 km depth subduction process. Amphibole eclogite fades metamorphic peak stage of 17-20 kbar and 600-700 degrees C occurred during similar to 2.1 Ga continental collision. Tectonic exhumation-related decompression during collision probably triggered partial melting of the eclogitic rock. Finally, decompression late stage estimated between 5 and 8 kbar and 550-650 degrees C under amphibolite fades overprint during orogenic collapse was responsible for appearance of kelyphitic reaction rims (symplectite) around garnet crystals. As its Paleoproterozoic contemporary analogues from Congo Craton, the Itaguara retroedogite is one of the oldest records of the modern-style plate tectonics. (C) 2020 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.