LAUSR

Heat flow and heat production datasets constrain the crustal thermal structure in the 2.5-3.5 Ga Bundelkhand craton, the oldest cratonic core in northern Indian shield, for the first time and allow comparisons with the southern Indian shield. Temperature measurements carried out in 10 boreholes at five sites in the craton, combined with systematic thermal conductivity measurements on major rock types yield low heat flow in the range 32-41 mW m-2, which is distinct from the generally high heat flow reported from other parts of the northern Indian shield. Radioelemental measurements on 243 samples of drill cores and outcrops reveal both large variability and high average heat production for the Neo-Archaean to Palaeo-Proterozoic granites (4.0±2.1 (SD) μWm-3) relative to the Meso-Archaean TTG gneisses (2.0±1.0 (SD) μWm-3). On the basis of new heat flow and heat production datasets combined with available geological and geophysical information, a set of steady-state, heat flow - crustal heat production models representative of varying crustal scenarios in the craton are envisaged. Mantle heat flow and Moho temperatures are found to be in the range 12-22 mW m-2 and 290-420 oC respectively, not much different from those reported for the similar age Dharwar craton in southern India. This study reveals similar mantle thermal regimes across the northern and southern parts of the Indian shield, in spite of varying surface heat flow regimes, implying that much of the intra-province and inter-province variations in the Indian shield are explained by variations in upper crustal heat production.