Palaeo-Neoproterozoic Tectonic Evolution of the Betul Belt in the Central Indian Tectonic Zone: A Petrochronological Study

ABSTRACT The present study from the Betul Belt in the Satpura Mobile Belt (SMB) is based on geochemical, petrological, and geochronological data from the mica schists and associated granite gneisses. Geochemical characteristics of the gneisses establish that they are peraluminous S-type granites formed in a collisional tectonic setting by partial melting of metasedimentary rocks. Geochemical signatures of the associated metasediments imply their deposition in an active continental margin. U-Pb isotope ages retrieved from the zircons of the granite gneisses constrain their emplacement age at ~1600 ± 50 Ma, which overlaps with the oldest monazite ages from the metasediments. This tectonic event is correlated with the granulite facies event recorded from the southern part of the SMB during an accretionary orogeny when the Gotosindhu, a Palaeoocean between the North India and South India Blocks (NIB and SIB), subducted below the SIB. The pervasive NW-SW trending S2BT foliation recorded from the two lithological units was syntectonic with the second metamorphic event M2BT that led to the garnet formation in the mica schists. P-T conditions of the M2BT event have been determined to be ~6 kbar, 570-610°C from isopleth thermobarometry and conventional geothermobarometry. Metamorphic monazites from the mica schists and the gneisses constrain the timing of the M2BT event between 968–901 Ma (EPMA chemical ages), and more precisely at 936.6 ± 1.5 Ma (U-Pb isotope age). This tectono-metamorphic event is coeval with the gamut of ~1.0–0.9 Ga tectonic events recorded throughout the Greater India Proterozoic Fold Belt, marking the amalgamation of the NIB and SIB.