Sm‐Nd Isotopic Evidence for Late Mesoproterozoic Metamorphic Relics in the East African Orogen from the Schirmacher Oasis, East Antarctica

Abstract Chronology of early metamorphic events preserved as relics in the Late Neoproterozoic–Cambrian Orogen in Dronning Maud Land, East Antarctica, are important to refine models that aim to reconstruct Gondwana and constrain earlier Mesoproterozoic continental configurations. In the nunatak Veteheia, south of the Schirmacher Oasis, near‐anhydrous metamorphosed noritic boudins within metapelitic granulite preserve an early medium‐pressure (∼8 kbar, 800°C) granulite facies assemblage. The retrograde PT segment of the dominant superposed tectonometamorphic cycle in granulites from the Schirmacher Oasis shows an early stage of near‐isothermal decompression, followed by a near‐isobaric cooling within the field of sillimanite stability. Two boudinaged metanoritic dykes preserving partially broken down garnet porphyroblasts with decompression‐cooling‐related textures were sampled and dated by the Sm‐Nd and Rb‐Sr isotopic methods. Leucocratic noritic anorthosite boudin yields a whole‐rock garnet Sm‐Nd isochro...