The work?was carried out?at the Department of Geology, University of Calcutta. The analytical work?was partly funded?by the UGC-UPE-II given to the University of Calcutta under the Non-focus Area Programme. The Research Fellowship in Sciences for meritorious students (RFSMS) of the University Grants Commission, Government of India, awarded to Susmita Das (No. F.7-47/2007 BSR), along with the Research and Fieldwork grants of the University of Calcutta given to Bapi Goswami, are all gratefully acknowledged. We thank Dr. S. Nandy and Sir S.K. Tripathy (EPMA Laboratory, CHQ, GSI,?Kolkata) for providing electron microprobe facilities. We are indebted to Prof J. Mukhopadhyay,
Reports of shoshonitic rocks in Precambrian terrains are relatively rare. Pl-Grt amphibolites and Hbl-Bt mafic granulites occurring in the migmatitic gneisses of the Chhotanagpur Gneissic Complex (CGC) show calc-alkaline and shoshonitic characteristics. Relict porphyritic, sub-ophitic and poikilitic textures are noted in these rocks. Their parent magma was emplaced during the waning phase of the regional metamorphism. Geochemically, these?metamafics are similar to the Group III potassic and ultrapotassic rocks of Foley et al. (1987). The magma was derived from the metasomatized subcontinental lithospheric mantle (SCLM). Subduction-related sediment melts metasomatized the SCLM. Compositionally, The emplacement of shoshonitic magma and subsequent decompression happened at the slab break-off stage of continental collision (~990 Ma).
Bapi GOSWAMI, Susmita DAS, Ankita BASAK, Chitta BHATTACHARYYA.2023. Discovery of Early Tonian Calc-alkaline and Shoshonitic Metamafic Rocks from the North Purulia Shear Zone, Chhotanagpur Gneissic Complex, Eastern India: Implications of Proterozoic Sub-continental Lithospheric Mantle[J]. Acta Geologica Sinica(),97(1):68-89Copy