Late Paleoproterozoic clockwise P–T history in the Mahakoshal Belt, Central Indian Tectonic Zone: Implications for Columbia supercontinent assembly

Abstract

The Paleo/Neoproterozoic Central Indian Tectonic Zone (CITZ) suggested being continuous with the Capricorn Orogen of Western Australia (COWA) and the Trans North China Orogen (TNCO) is the zone of accretion between the North India and the South India Archean Blocks. This study aims to establish the tectonothermal history of the Mahakoshal Belt (MB) in the CITZ and to review its relevance to the suggested correlation of CITZ with COWA and TNCO. In this study, we focus on the metamorphic P–T–t history of phengite–quartz–andalusite–margarite–muscovite–chlorite–biotite schists/phyllites and rare andalusite–corundum–quartz veins in the schists/phyllites. S1 inclusion trails of phengite+biotite+quartz±muscovite±chlorite assemblages in syn/post-S2 andalusite porphyroblasts were stabilized at ∼8kbar, 520°C. Near-isothermal decompression led to andalusite–muscovite stabilization at the expense of phengite-bearing assemblage at <4kbar. Continued isothermal decompression (2–3kbar) led to fluid-aided post-S3 replacement of andalusite porphyroblasts by margarite–muscovite–chlorite pseudomorphs, and andalusite–corundum in the veins were replaced by muscovite–diaspore±chlorite assemblages. U–Th–Pb (total) age determinations suggest that the clockwise P–T path in the MB schists/phyllites occurred at 1.7–1.8Ga, which overlaps with the 1.7–1.8Ga granitoids in the supracrustal belt. This Paleoproterozoic subduction-metamorphism and granitoid emplacement synchronous with exhumation in the MB combined with existing information suggest that the CITZ comprised disparately-evolved crustal domains that accreted over a protracted time between Late Paleoproterozoic and Early Neoproterozoic. The tectonothermal events in the CITZ partly overlap with those in the COWA and TNCO with major omissions, and therefore, these global correlations should await further petrological and robust age determinations in the CITZ.