TRANSITIONS IN PALEOARCHEAN GEODYNAMIC AND EARLY LIFE ENVIRONMENTS, BARBERTON GREENSTONE BELT, SOUTH AFRICA

One of the best places to investigate the evolution of early Earth marine environments and potential habitats for microbial life is the 3.56 – 3.1 Ga Barberton greenstone belt (BGB) of South Africa. The BGB contains some of the world’s best preserved sequences of volcano-sedimentary and hydrothermally altered mafic-ultramafic oceanic rocks representative of the Paleoarchean Eon. These rocks provide a unique opportunity to investigate early Archean atmospheric conditions, low-temperature subseafloor fluid-rock interactions, evidence for microbial life and biogeochemical cycling on our young Earth^[1]. New field, petrological, geochronological and geochemical data will be presented across the stratigraphy of the BGB focusing on major geological transitions that mark dynamic changes in environmental settings that, in turn, may have provided new ecological niches for early life^[2,3,4]. New data presented will address the onset of plate-tectonic processes in the BGB, major transitions in mafic-ultramafic volcanic activity, and other secular geodynamic processes preserved throughout the BGB stratigraphy. Links and potential feedbacks between crustal surface processes, sulfur biogeochemical cycling and sequestration of atmospheric CO₂ across the Paleoarchean Eon will also be explored.

[1] Grosch, E.G., McLoughlin, N., de Wit, M.J, Furnes, H. (2009b). Deciphering Earth’s Deep History: Drilling in Africa’s Oldest Greenstone Belt. Eos, vol. 90, No. 40, 350-351.

[2] Grosch, E.G., Kosler, J., McLoughlin, N., Drost, K., Slama, J., Pedersen, R. B., (2011). Paleoarchean detrital zircon ages from the earliest tectonic basin in the Barberton Greenstone Belt, Kaapvaal craton, South Africa. Precambrian Research, 191, 85-99.

[3] Grosch, E.G., Vidal, O., Abu-Alam, T., McLoughlin, N., (2012). PT-Constraints on the metamorphic evolution of the Paleoarchean Kromberg type-section, Barberton Greenstone Belt, South Africa. Journal of Petrology, 53(3), 513-545.

[4] Grosch, E.G. and McLoughlin, N. (2013). Paleoarchean sulfur cycle and biogeochemical surface conditions on the early Earth, Barberton, South Africa. Earth and Planetary Science Letters, 377 - 378, 142 - 154.