Towards a crustal thermal model for the Archaean Dharwar craton, southern India

Abstract

New heat flow and heat production data from the Archaean Dharwar craton of southern Indian shield refine crustal thermal models and mantle heat flow estimates. The terrain comprises greenstone–granite belts and gneisses, which give way to granulites farther south. Low heat flow, generally spanning a range from 25 to 51 mW m −2 with a mean of 36 mW m −2 characterizes the craton. However the radiogenic heat production of surface rocks varies widely, from 0.2 to 8 μW m −3. Based on considerations of heat flow, regional geology, crustal sections constrained by deep seismic sounding and gravity data, and extensive heat production data for rock types comprising the crustal sections, four one-dimensional scenarios are envisaged for crustal heat production in the province. These are compatible with the range of the observed surface heat flow and represent the plausible extremes in the crustal heat contribution, on a regional scale. The heat flow at the base of the crust is found to have a small range, 12–19 mW m −2 for the craton. This range is similar to those derived for Archaean provinces in the Canadian and southern African shields. The regional model provides robust bounds for crustal temperature estimates in the craton, with a range of 285–410 °C at the Moho, which points to a generally ‘cold’ crust in the region.