Open AccessHigh μ (HIMU) ocean island basalts in southern Polynesia: New evidence for whole mantle scale recycling of subducted oceanic crust
Author(s) -
Kogiso Tetsu,
Tatsumi Yoshiyuki,
Shimoda Gen,
Barsczus Hans G.
Publication year - 1997
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/96jb03892
Subject(s) - basalt , mantle (geology) , geology , oceanic crust , geochemistry , subduction , adakite , paleontology , tectonics
Major elements, trace elements, and Pb isotopic compositions were determined for ocean island basalts (OIBs) from Polynesia in the southern Pacific in order to document the chemical characteristics of OIB sources and to understand their origin. High μ (HIMU: μ= 238 U/ 204 Pb) basalts, which have distinctly high Pb isotopic ratios, have systematically different compositions from non‐HIMU basalts; HIMU basalts are more enriched in Fe 2 O 3 *, MnO, and CaO and more depleted in SiO 2 , K 2 O, P 2 O 5 , Ni and incompatible trace elements than non‐HIMU, except for Nb. Major element characteristics of HIMU basalts suggest that the HIMU source is more fertile, i.e., more enriched in a basaltic component, than non‐HIMU sources. This is consistent with the suggestion that subducted oceanic crust may contribute to the formation of the HIMU reservoir. Relative depletion of incompatible trace elements in HIMU is consistent with involvement of sedimentary components in non‐HIMU sources. However, enrichment of Nb relative to other incompatible elements in HIMU cannot be explained by simple addition of the crustal component nor partial melting processes in the upper mantle, implying that lower mantle processes may contribute to the formation of the HIMU source.