Trace element and isotopic evidence for Archean basement in the Lonar crater impact breccia, Deccan Volcanic Province

The basement beneath the Lonar region is believed to be similar to the Dharwar craton of peninsular India. Based on their similar Pb-isotopic compositions with the breccia rocks, we suggest the Archean Chitradurga Group of rocks of this craton to be present in the basement beneath the Deccan lavas of the Lonar region. The thickness of the basaltic target rocks at the crater-site (∼ 400 m) and the inferred crater depth (350 m-610 m), based on depth to diameter ratios in simple planetary craters (0.2-0.33), are consistent with our conclusion regarding melting and incorporation of these ancient basement rocks in the impact breccia of the Lonar crater. Using Pi-group scaling relations, the observed crater diameter, and density of the basaltic target rocks, we have estimated with reasonable approximation the diameter of the Lonar impactor to be either 70 m, 86 m or 120 m, assuming the bolide to be an iron meteorite, stony-iron meteorite, or an ordinary chondrite, respectively.