ITAPECERICA METAMAFIC-ULTRAMAFIC ROCKS WITH E-MORB SIGNATURE: OPHIOLITIC REMNANTS OF THE RHYACIAN-OROSIRIAN OROGENY IN SOUTHERN SÃO FRANCISCO CRATON?

Rochas metamáficas-ultramáficas com assinatura E-MORB na região de Itapecerica: remanescentes ofiolíticos da Orogenia Rhyaciana-Orosiriana no Sul do Cráton São Francisco?

Abstract

In the Southern São Francisco Craton near Itapecerica (Minas Gerais – Brazil) occurs a supracrustal succession of rocks, varying from bottom to top by quartzite, graphite schist, khondalitic paragneiss and banded iron formation whose protoliths are from oceanic basin with ages in the context of the Rhyacian-Orosirian orogeny. Amphibolite and metaultramafic bodies occur associated to this succession. Mineralogical and textural features of the amphibolite allow suggesting a gabbroic protolith metamorphosed to granulite facies and retrometamorphosed in amphibolite facies to generate the amphibolite. Geochemistry reveals tholeiitic affinity to the amphibolite protolith, which has an E-MORB signature, associating this rock to an oceanic setting. The association of amphibolite to metaperidotite in oceanic setting suggest the transition of gabbro to ultramafic rocks in a typical ophiolite sequence. A possible suture zone in the Itapecerica/Claudio region formed by the collision between Divinopolis and Campo Belo/Bonfim complexes during the Rhyacian-Orosirian orogeny involving the Itapecerica oceanic basin alongside Claudio Shear Zone and forward to Minas Basin is a suggestive geological setting of the investigated region.