Clay mineralogical and geochemical evidences of lateritic weathering at about 2.2 ga prior to the evolution of life on earth

This study incorporates a well-developed lateritic profile occurring within the Aravalli Supergroup sediments of 2200 Ma-1850 Ma age from Rajasthan, Western India. The lateritic paleosol exposed in a 60 m query was studied for field characteristics, clay mineralogy, and geochemical features to assess weathering and paleoclimatic conditions during Precambrian. The paleosol is marked by intense weathering with deep-red and light orange colours, massive to friable blocky structure, which progressively grades down to unaltered dolomite in the lower most part. The X-ray diffraction studies of the total clay (\u003c2 μm) and the fine clay (\u003c0.2 μm) fractions of the lateritic paleosols are characterized by 7A°, 3.58 A°, 3.52 A°, and 3.03A° mineral assemblage dominated by the kaolinite and anatase in large amounts. Other clay minerals include halloysite, mixed layers of kaolinite-halloysite, and calcite-veterite in small proportions. The energy dispersive X-Ray spectrometry (EDS) analysis of a few concretions show large scale enrichment of Al, Fe and Ti and the losses of the Ca, Mg, Na, and K during weathering and formation of the clay minerals. These features provide the evidence of intense weathering conditions under hot-humid climate leading to the formation of laterite prior to evolution of life on Earth at about 2.2 Ga.