Geochemistry and mineralogy of the 2.45 Ga Pronto paleosols, Ontario, Canada

In the samples from both sites, the ratios of Al/Ti and Si/Ti decrease toward the top of the profile. Together with the destruction of minerals toward the unconformity, such as apatite, biotite and chlorite, the depletion of Al and Si suggests that the parental granite was weathered by an acidic weathering solution. During the Archean-early Proterozoic era, the high atmospheric partial pressure of CO2 (pCO2) is the most probable candidate for producing the acidic weathering solution.