20-EPN2-057: A Zircon Provenance Study of the Kanye Basin (Botswana) to Constrain Terrestrial Geodynamics Across the Archaean-Proterozoic Transition.

Virtual visit by Denice Borsten and Jochem Sikkes (Vrije Universiteit Amsterdam, Netherlands) to TA2 Facility 26 – KBSI Sensitive High Resolution Ion MicroProbe / SHRIMP-IIe/MC (South Korea).
Dates of visit: 23 September 2021 -17 February 2022

Report Summary: This study investigates the Neoarchaean to Paleoproterozoic Transvaal Supergroup sedimentary sequence in Botswana that formed in the centre of the Kaapvaal Craton during the early oxygenation of the atmosphere. We used U-Pb dating on magmatic and sedimentary zircons from throughout the sedimentary sequence to determine the tectono-magmatic evolution of the hinterland basement. This approach constrains regional crustal growth, uplift and erosion events and establishes if additional cratons were in the hinterland, e.g. Pilbara. Knowledge of zircon provenance will allow critical comparison to known tectonic scenarios, e.g. Alpine style molasse basin and any potential change in Neoarchaean tectonics by considering erosion and crustal growth-reworking. The geochronology results help evaluate spatial and temporal variations in depositional environments associated with oxygenation of the atmosphere. Results indicate that the age of the basement, Gaborone Granite and the Kanye volcanic are indistinguishable (2768.9 ± 6.0 Ma). Sediments deposited from 2.642 Ga to 2.550 Ga are also dominated (> 90%) by zircons of ~2.77 Ga. This implies that there was a major crustal growth event in the Kanye region at 2.77 Ga that included minimal crustal reworking. Erosion products to the Kanye Basin are derived from this juvenile crust throughout the Archaean and Proterozoic until > 2.0 Ga.  Only then are older and younger basement rocks recorded in the sedimentary sequence. This region of the planet yields no evidence of a major tectono-magmatic event associated with the oxygenation of the atmosphere.