Riassunto analitico
Objective of the study is to reconstruct the nature and timing of the processes that generated the heterogeneities inferred for the mantle source beneath the Vema region at 11°N on the Mid Atlantic Ridge. A large number of mantle peridotites are analyzed for Os sistem and major element abundances. The analytical work has been carried out during the international traineeship at the Institute of Geology and Geophysics of the Chinese Academy of Sciences (IGGCAS) in 2019. The thesis work moves from the recognition of a regional-scale (hundreds of km) heterogeneity in the suboceanic mantle source based on the inconsistency of the degrees of melting inferred from erupted basalts and their associated mantle residua. The suboceanic mantle source has been brought beneath the ridge by the Giga years-lasting whole mantle convection. Any lithological or compositional difference results from events far back in time, requiring the use of an isotopic methodology able to describe events occurred on the Ga scale. The Os isotopic system, based on the long-lived β- transition of 187Re to 187Os, has matured to wide use in high temperature geochemistry. Peridotite samples dissolved through a Carius tube to digest and oxidize Os, have been spiked to obtain the concentration of the HSE in the samples and measured by the Thermal Ionization Mass Spectrometer for Os isotopes.
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