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The role of mantle plumes in the formation of Large Igneous Provinces: constraints from noble gases

Principal Investigators: Dr. Nicole A. Stroncik, Dr. Samuel Niedermann

Mantle plumes are upwellings of large volumes of mantle material in focused conduits considered to originate from deep within the mantle. Plume heads are the leading ends of such upwellings. Large igneous provinces (LIPs) are thought to have formed by magmatism resulting from plume head decompressional melting. However, the evidence for this theory of LIP formation is mixed and it has been challenged lately. In this context noble gas isotopes are important as a discriminator of deep-mantle origin because of the large and indicative isotope variations existing between the various terrestrial reservoirs. One of the main arguments for a plume origin of Continental Flood Ba-salt (CFB) magmas is excess 3He compared to MORB. High 3He/4He ratios have been found, e.g., in the Afar and Columbia River CFB provinces. Noble gas data from the Paraná-Etendeka LIP do not exist and the He isotope data available from the Tristan da Cunha hotspot are not meaningful. Thus we propose a noble gas study of samples from Tristan da Cunha, Etendeka and Paraná to constrain the mantle components involved in the formation of CFB and hotspot lavas and to shed some light on the role of plumes in LIP formation.