Interpretation of 40Ar/39Ar geochronological data to infer mineralization events in Archean terranes: Comment on Bineli Betsi et al. (2025)

Abstract

In spite of the wide use of ⁴⁰Ar/³⁹Ar geochronology of potassium-bearing minerals to date mineral deposits, caution needs to be exercised in the interpretation as there is a high chance that the ages have been modified by subsequent events not related to the mineralization. This comment addresses the contentious nature of the c.550 Ma ⁴⁰Ar/³⁹Ar hydrothermal K-feldspar ages from the Mowana copper deposit in NE Botswana, and used by Bineli Betsi et al. (2025) to invoke a much younger mineralization event not compatible with known geologic events within the host Archean terrane. Comparable U-Pb zircon lower intercept ages are widely reported from the different Archean terranes in the region, and shown to be a common result of sub-recent weathering-related Pb-loss. The highly disturbed nature of the ⁴⁰Ar/³⁹Ar spectra presented in Bineli Betsi et al. (2025) is a testament to the modification of the dated K-feldspar and the obtained ages are re-interpreted to indicate alkali redistribution related to weathering in the Archean hinterland. Instead, the Paleoproterozoic ages obtained by earlier studies from Pb-Pb sulphides are suggested to be closer to the timing of mineralization at the Mowana copper deposit.