Mantle geochemistry: Insights from ocean island basalts

摘要: The geochemical study of the Earth’s mantle provides important constraints on our understanding formation and evolution Earth, its internal structure, dynamics. bulk Earth composition is inferred by comparing terrestrial rocks with chondrites, which leads to chondritic model. That is, has same relative proportions refractory elements as that in but it depleted volatiles. Ocean island basalts (OIB) may be produced plumes possible deep origins; consequently, they provide unique opportunity Earth. Isotopic variations within OIB can described using a limited number endmembers, such EM1, EM2 HIMU, have been used decipher processes. Introduction crustal material into via subduction delamination generating heterogeneity; however, there active debate how were sampled melting, i.e., role olivine-poor lithologies petrogenesis. origin location high 3He/4He remain controversial, ranging from unprocessed (or less processed) primitive lower highly processed materials shallow origins, including ancient melting residues, mafic cumulates under arcs, recycled hydrous minerals. Possible core-mantle interaction was hypothesized introduce distinctive signatures radiogenic 186Os Fe Ni enrichment OIB. Small some short-lived nuclides, 142Nd, 182W several Xe isotopes, reported modern rocks, implying must differentiated first 100 Myr formation, not efficiently homogenized convection.