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Composition and melting conditions of primary mantle magmas in the Etendeka igneous province, NW Nambia, from melt inclusion and phenocryst microanalysis

Principal Investigator: Dr. Robert Trumbull TrumbullRundeI

Information about the primary magma compositions, the nature of mantle components involved, and the P-T conditions and degree of melting is of central importance to understanding mantle processes associated with intensive magmatism and continental breakup in the South Atlantic. The Paraná-Etendeka flood basalt province has been extensively studied but controversy remains about the source and composition of primary magmas and underlying causes in the mantle. This project aims to go further than previous work in two ways; first, we build on information and experience from existing work and concentrate on relatively rare, high-Mg, olivine-bearing rocks from NW Namibia which are most likely to preserve primary melt information. Second, we utilize advances in microanalytical techniques to obtain major and trace element analyses of early-formed phenocrysts and melt inclusions preserved within them. This work will constrain key source parameters (Mg/Fe and Ca/Al ratios, trace element signatures) that control mantle melting and distinguish source components, and it will provide estimates of temperature-pressure conditions and degree of melting required to evaluate mantle processes by numerical modelling. Additionally, melt inclusions may preserve pre-eruptive volatile contents (H2O, CO2, Cl, S), which have a major influence on melting relations and are relevant for assessing the environmental impact of large igneous events.