Remnant of upper granulite continental crust in the Maurice Ewing Bank Complex (DSDP site 330, east Falkland-Malvinas Plateau) and role in Grenville orogeny

Abstract

Abstract The Mesoproterozoic crust of remnant terranes such as Maurice Ewing Bank can provide crucial clues about Rodinia supercontinent. Petrological and geochemical studies were conducted to unravel the metamorphic history of the Maurice Ewing Bank Complex (MEBC). The MEBC is a polyphase metamorphic terrane with four progressive tectono-metamorphic events in subduction-related rocks. The first two episodes (R1-R2) occurred under conditions of progressive amphibolite- and granulite-facies metamorphism related to an orogenic hinterland. The R2 episode (P\u202f=\u202f1.05\u202fGPa, T\u202f=\u202f800\u202f°C) coincided with an older syn-deformational metagranitoid age of 1068\u202f±\u202f28\u202fMa. The third episode (R3) involved granulite-facies metamorphism (P\u202f=\u202f0.7–0.9\u202fGPa, T\u202f=\u202f830–930\u202f°C) during tectonic exhumation that led to generation of syn- to late metagranitoids at 1032\u202f±\u202f12\u202fMa. Episode four (R4) was marked by a regional anatectic process linked to crustal delamination at 1006\u202f±\u202f13\u202fMa. Late retrograde metamorphic events, demonstrated by Rb-Sr and K-Ar isotopes, were generated by far-field thermal anomalies of Neoproterozoic-Palaeozoic tectonic events such as the Pan-African orogeny and Gondwanides. The correlation of the geotectonic environment and coeval magmatic-metamorphic events indicates that the MEBC comprises the roots of an orogenic hinterland of the Natal-Maurice-Maud belt during Rodinia-forming orogenies caused by the interaction of Kaapvaal and Patagonia cratons.