Eruptive Styles, Magma Plumbing Systems, And Magma/Sediment Interaction In A 1.2 Ga Calc-Alkaline To Shoshonitic Volcanic Arc Setting, Sw Namibia

Abstract

The 1.2 Ga Barby Formation contains a volcanic arc stratigraphic succession up to 8.5 km thick and lies within the Konkiep terrane of SW Namibia. These rocks have not been previously studied in a modern volcanological context. Detailed mapping of a representative section of the Barby Formation shows a complex sequence of pyroclastic fall deposits, lacustrine sediments, diatreme feeder conduits, and hypabyssal intrusions. Outcrops in the study area also show extensive exposures of pyroclastic rock with intrusive contacts against lacustrine sediments. Major and trace element analysis of rocks in the study area indicates they are calc-alkaline to shoshonitic in composition.