Chapter 5.4 Volcanology of the Barberton Greenstone Belt, South Africa: Inflation and Evolution of Flow Fields

Abstract

Publisher Summary This chapter describes the volcanology of the Barberton Greenstone belt, South Africa. In greenstone belts, most volcanic sequences were mantle melts that erupted in submarine tectonic settings before they were deformed during the assembly of continental lithosphere. The Barberton Greenstone Belt (BGB) offers a unique opportunity to research the Earth's oldest remnants of seafloor crust–komatiite-bearing volcanic sections with well-preserved textures and minerals. The volcanic rocks are locally hydrothermally altered on the seafloor beyond recognition to cherts and carbonates. The Komati Formation has two members that include a lower member of alternating layers of komatiite and komatiitic basalt, and an upper member dominated by pillowed and massive flows of komatiitic basalt. In the Lower Komati, five layers of komatiite share the same zoning, and yet each layer is geochemically distinct. The flow fields of komatiitic basalt in the Lower Komati are 80% sheet flows with interlayered pillows. The Mendon Formation conformably overlies the Kromberg Formation and consists of lava flows of komatiite and komatiitic basalt interlayered with cherts or silicified volcaniclastic sediments.