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 degrees C at 0.1-0.2 GPa to stabilize amphibole and garnet via a series of dehydration and decarbonation reactions forming 10-50 mu m 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-ThO2 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-ThO2 domains that laced the low-ThO2 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 similar to 3200 Ma metamorphic event in the Bundelkhand craton is similar to those reported from the Singhbhum and the Dharwar cratons. The similar to 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.

Automated summary

The study reveals that the BIFs in the Bundelkhand craton were formed through metamorphism, with P-T pseudosection analysis providing insight into the temperature and pressure conditions during their formation. The U-Th-Pb analysis of monazites demonstrates three distinct age clusters, indicating different metamorphic events.