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The Cambrian Nongpoh granitoids, intrusive into the Precambrian gneissic complex and metasediments of the Shillong Group, represent a major phase of granitic magmatism in the Shillong Plateau. The Nongpoh granitoids comprise diorite, granodiorite, porphyritic and grey granites. Porphyritic granite is the dominant lithology exposed in the Nongpoh granitoids, and contains three types of enclaves, viz. xenoliths of gneissic rocks, dark grey porphyry and biotite-rich microgranular enclaves. The mafic magmatic enclaves (MMEs) of various dimensions and shapes, including rounded, ellipsoidal, rectangular, angular to subangular, and stretched bodies, were produced by evolving nature and contrasting kinematics of interacting felsic and mafic magmas. The biotite-rich enclaves are due to the injection of syn-magmatic mafic dykes in felsic magma. The various textural assemblages and sub-linear variations between silica and major oxides, chemical mixing and element diffusion suggest that multistage magma hybridization was the key process during the evolution of the Nongpoh granitoids. The 501 Ma age obtained by chemical (U–Th–Pb) dating of monazite in MME ascertained the age of the magma hybridization event in the Nongpoh granitoids, which is equivalent to the igneous activity at 500 Ma during the amalgamation of Eastern Gondwana.

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The 600–660 Ma East African Orogen (EAO) granulites of the Mozambique Belt were correlated and extended into a coast marginal area of East Antarctica through the NNW–SSW-trending granulite-bearing Schirmacher Oasis. Tracing similarities in lithological association, granulite-facies metamorphism and geochronological data, the 640 Ma EAO was extended by another 110 km south of Schirmacher into the Humboldt Mountains in central Dronning Maud Land (cDML). Based on younger anorogenic magmatism east and west of the Humboldt Mountains, a 10–20 km-wide linear corridor of the EAO from the Schirmacher to the Humboldt Mountains was proposed.There are eight nunataks between Schirmacher and the Humboldt Mountains projected above the ice sheet. These nunataks are strategically placed because they represent the small (4–10 km2), isolated rock exposures in approximately 5000 km2 of ice-covered area. Baalsrudfjellet is one of these nunataks that is located at the easternmost margin of the proposed EAO corridor and represents a significant outcrop to validate the presence of the EAO between Schirmacher and the Humboldt Mountains. This study brings out a two-stage metamorphic evolution (c. 660–680 Ma and c. 580 Ma) with melt generation associated with the younger event. Geochronological constraints by monazite chemical dating from metapelites confirm and validate the continuation of the EAO in-between the Schirmacher Oasis and the Humboldt Mountains.Supplementary material: Monazite analyses, computed ages and age errors of three grains from the high- and low-melt metapelite are available at https://doi.org/10.6084/m9.figshare.c.3738362