Proterozoic High-Temperature-Low-Pressure Metamorphism in the Mahakoshal Belt, Central Indian Tectonic Zone (India): Structure, Metamorphism, U-Th-Pb Monazite Geochronology, and Tectonic Implications

To understand the protracted accretionary evolution along the Central Indian Tectonic Zone (CITZ), we investigated garnet-staurolite schists and associated lithologies from the central Mahakoshal Belt (MB). Mesoscale structures, porphyroblast growth, garnet zoning, and pseudosection modeling were coupled with U-Th-Pb monazite dating to reconstruct a clockwise pressure-temperature-time (P-T-t) path for the garnet- and staurolite-bearing schists. The prograde path is characterized by near isobaric heating conditions, which initiates at pressure-temperature (P-T) conditions of 4.5-5.0 kbar and 550 degrees-560 degrees C and attains peak metamorphismat 5.5-6.0 kbar and 610 degrees-620 degrees C. The peak metamorphism was contemporaneous with the emplacement of southern-margin granitoids at similar to 1.70 Ga, resulting in the perturbation of geotherms in the collision setting. The retrograde arm (MR) of the P-T path passes through isobaric cooling at similar to 5.0 kbar and similar to 500 degrees C. This late Paleoproterozoic P-T-t path is overprinted by hitherto uncharacterized tectonism that coincides with the Sausar orogeny and provides evidence for the northward extension of 0.95-0.85 Ga orogenic activity within the CITZ. The 1.80-1.55 and 0.95-0.85 Ga tectonothermal events identified in this study support that crustal evolution in the CITZ involved a mosaic of domains that were accreted together in the Neoproterozoic time.

Automated summary

By investigating garnet-staurolite schists and associated lithologies from the central Mahakoshal Belt, a clockwise pressure-temperature-time path was reconstructed to understand the protracted accretionary evolution along the Central Indian Tectonic Zone. The study revealed a mosaic of domains in the CITZ that were accreted together in the Neoproterozoic time, showing evidence of different tectonothermal events at 1.80-1.55 and 0.95-0.85 Ga.