Volatile abundances and their spatial distributions provide important constraints on models of mantle melting, mantle convection and crustal recycling. The role of water is crucial especially for intra-plate oceanic magmas originated beneath a thick lithosphere, where small degrees of melting represented by many OIB, may only be possible due to its presence. However, the rarity of naturally quenched glasses at these locations has greatly limited OIB studies, and only scarce data are available.
The present project will fill this gap, quantifying the amount of water in typical ocean islands, its control on melting and its implications for the origin of their sources. In this frame, the recent improvement of the analytical techniques for melt inclusions analyse s, has made them a powerful tool for investigation, since they preserve their original, un-degassed, volatile contents. H2O and CO2 contents, trace elements and Pb isotopes will be determined in olivine hosted primary melt inclusions from typical OIB from Canary (La Palma) and Cape Verde (Santo Antao, Fogo) islands.
The selected localities display an isotopic composition with clear HIMU signature, which has been related to the presence of dehydrated oceanic crust. Thus, assessing the volatiles concentration s and their relationship to key radiogenic isotopic signatures in intra-plate OIB, will provide both major insight into the role of recycling in the mantle and its importance in controlling mantle melting away from the mid-oceanic ridges. Pb-Li isotope com position on whole rocks will also be measured, in order to investigate with novel isotopic tracers the relationship between volatile contents and the different isotopic signature of the mantle sources, and to put constraints on mantle convection and crustal recycling processes. These objectives will be achieved developing appropriate in situ analytical procedures with state-of-the-art instruments for both geochemical and isotopic analyses.
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