Phase relations and in-situ U-Th-Pbtotal monazite geochronology of Banded Iron Formation, Bundelkhand Craton, North-Central India, and their geodynamic implications

The Bundelkhand craton hosts Banded Iron Formation (BIF) bodies within the east–west trending Bundelkhand Tectonic Zone (BTZ). The BIFs near Mauranipur, BTZ, are massif and are composed of amphibole, quartz, magnetite, and garnet. P–T pseudosection analysis implies that the protolith of these BIFs were carbonate-bearing sediments that underwent metamorphism at 400–450 °C at 0.1–0.2 GPa to stabilize amphibole and garnet via a series of dehydration and decarbonation reactions forming 10–50 µm sized monazite grains in the process. The U-Th-Pb ( n = 74) analyses by the electron probe microanalyzer yield three age clusters. The oldest mean age, 3137 ± 96 Ma, is retrieved from low-ThO 2 monazites occurring as discrete grains within amphibole bands and is interpreted as the timing of monazite growth caused by fluid-rock interaction. The second age cluster yields an average age of 2567 ± 48 Ma from high-ThO 2 domains that laced the low-ThO 2 monazite core. Anhedral monazites occurring as inclusions within garnet yield an average age of 2538 ± 120 Ma. These 2500 Ma dates reflect monazite growth during prograde metamorphism. An age of 2168 ± 83 Ma is retrieved from monazite overgrowths in amphibole bands. The ~ 3200 Ma metamorphic event in the Bundelkhand craton is similar to those reported from the Singhbhum and the Dharwar cratons. The ~ 2500 Ma age, when compared with the available geochronological data, constrains the timing of Neoarchean-Paleoproterozoic tectonism and stabilization. The minor Meso-Paleoproterozoic (2100–1900 Ma) age may be related to extension and dyke emplacement.