Lithospheric Controls on Flood Basalt Volcanism

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EAR-0309057Elkins-TantonContinental flood basalt provinces are enigmatic due to their infrequency in the geologic record, their remarkable size (at least 105 km3 of lava), their speed of formation (the Siberian and several others were complete in about a million years) and their apparent or possible age coincidences with other terrestrial catastrophes, including extinctions, meteorite impacts, and sea level changes. The Siberian flood basalt province, one of the largest, is also closely coincident in time with the Permian extinction, the largest in Earth history. Understanding the processes that trigger and create continental flood basalts therefore has relevance not only to geology and geophysics, but possibly to cycles of life on earth and certainly to interactions of global chemical systems. Flood basalts are a link between the evolution of the Earth and evolution of life on Earth.The work is designed to help differentiate among competing theories for the formation of flood basalts, and, more specifically, to create better understanding of the role of lithosphere in triggering and eruption. The project bridges the fields of experimental petrology and numerical modeling. The work will be carried out by the P.I. and will also constitute the undergraduate thesis of at least one Brown University undergraduate. The work will consist of two parts: 1. High-pressure and temperature experiments on high-MgO magmas from Siberia to assess their pressure and temperature of formation; and 2. Numerical modeling to study the role of lithospheric foundering as a magmatic focus and trigger, and to study lithospheric topography at the edge of cratons and how it affects plume ascent.This project will be one of the first experimental studies on primitive flood basalt compositions. The results of the experimental study have the potential to differentiate between models for lavas requiring very deep, hot melting, and models suggesting alternative mantle lithologies melting at lower temperatures. These results may significantly alter models for flood basalt formation.