Did Earth surface processes promote stabilization of the central Indian Bundelkhand craton?

The impact that ancient Earth surface processes had on long-term thermal regimes remain uncertain despite their potentially important role in fostering craton stabilization and preservation. The distribution and redistribution of heat producing elements (HPEs) during craton development plays a major role in lithospheric cooling and strengthening. Whereas the redistribution of HPEs via erosion has theoretically been suggested to alter the long-term geotherm and contribute to Moho cooling, direct temporal constraints from the field are lacking to adequately assess the role that ancient Earth surface processes may have had on long-term thermal regimes. Here, we used apatite U-Pb thermochronology to assess the thermal evolution of the Archean Bundelkhand craton of central India immediately following its amalgamation and final phase of silicic magmatism at ~2.5 Ga. Apatite from both ~3.4 Ga granitic gneisses and ~2.5 Ga granitoids collected across the ~250 km-wide craton yielded near-uniform apatite U-Pb dates between ~2.4–2.3 Ga, indicating that the craton was broadly exhumed through mid-crustal depths shortly following shallow granitoid emplacement. Unroofing of the craton at this time is further corroborated by the presence of a distinct ~2.5 Ga detrital zircon U-Pb age peak obtained from ~2.2–2.3 Ga sandstones in direct non-conformable contact with Bundelkhand granitoids. We speculate that a two-step redistribution of HPEs largely contributed to the stabilization of the Bundelkhand craton. First, the concentration of HPEs within shallowly emplaced granitoids at ~2.5 Ga reduced the heat production of the lower-most crust. Second, post-emplacement exhumation of HPE-enriched Bundelkhand granitoids further modified the heat source distribution to a thermal regime that promoted cooling of the lower-crust. Although the mechanism driving exhumation through mid-crustal depths remains uncertain, temporal relationships from the Bundelkhand craton suggest that erosional processes may have had a significant role in promoting the craton’s stability and longevity.