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Copyright © 2011 by The Geochemical Society of Japan. al., 2008). However, altered MORB becomes usually heavier in their Li isotopic ratios (δ7Li < +20.8‰) by seawater-alteration at low temperature. The δ7Li values of seafloor sediments are variable, ranging from 0 to +7‰ (Chan et al., 2002; Bouman et al., 2004). The Li isotopic composition might therefore be a useful tracer to investigate recycling of surface derived material into mantle if the isotopic signatures of subducted surface material are preserved during subduction and its storage in mantle. In spite of the variation of Li input in subduction, Li isotopic ratios of most OIB are constant and similar to those of MORB and normal mantle. Lithium isotopic compositions of Mauna Loa and Mauna Kea basalts from Hawaii range from +2.5 to +5.7‰ (Chan and Frey, 2003), thereby overlapping the range of MORB. The HIMU (Mangaia, Tubuai, Raivavae, and Rurutu) are characterized by Li isotopic ratios ranging from +5.0 to +7.9‰, and are slightly heavier than those of MORB (Nishio et al., 2005; Chan et al., 2009; Vlastelic et al., 2009). The Li isotopic ratios of Rapa lava, EM2-type, range from +3.7 to +5.9‰ (Chan et al., 2009). The few data available for EM1 lava samples, e.g., Pitcairn Island, (+3.3 to +4.1‰, Chan et al., 2006) display MORB-like values. Some basalts or xenoliths from continental settings also show EM1-like isotopic signatures. However, little data of Li isotopic composition have been reported on them. Lithium abundance and isotope composition of Logudoro basalts, Sardinia: Origin of light Li signature |
