New and published data on the composition of melt inclusions in olivine (Fo73–91) from volcanoes of the Kamchatka and northern supercritical liquid at deeper depths beneath the rear arc. The solute-rich slab component dominates the budget of LILE, LREE, Th Earth and Planetary Science Letters 255 (20...
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| Format: | Text |
| Language: | English |
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| Online Access: | http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.455.6416 http://www.plechov.ru/Publications/2007/Portnyagin2007EPSL.pdf |
| Summary: | New and published data on the composition of melt inclusions in olivine (Fo73–91) from volcanoes of the Kamchatka and northern supercritical liquid at deeper depths beneath the rear arc. The solute-rich slab component dominates the budget of LILE, LREE, Th Earth and Planetary Science Letters 255 (2007) 53–69 www.elsevier.com/locate/epsl⁎derived components. We demonstrate that typical Kamchatkan arc-type magmas originate through 5–14%melting of sources similar or slightly more depleted in HFSE (with up to ∼1 wt. % previous melt extraction) compared to MORB-source mantle, but strongly enriched inH2O, B, Be, Li, Cl, F, LILE, LREE, Th andU.MeanH2O in parental melts (1.8–2.6wt.%) decreases with increasing depth to the subducting slab and correlates negatively with both ‘fluid-immobile ’ (e.g. Ti, Na, LREE) and most ‘fluid-mobile ’ (e.g. LILE, S, Cl, F) incompatible elements, implying that solubility in hydrous fluids or amount of water does not directly control the abundance of ‘fluid-mobile ’ incompatible elements. Strong correlation is observed between H2O/Ce and B/Zr (or B/LREE) ratios. Both, calculated H2O in mantle sources (0.1–0.4%) and degrees of melting (5–14%) decrease with increasing depth to the slab indicating that the ultimate source of water in the sub-arc mantle is the subducting oceanic plate and that water flux (together with mantle temperature) governs the extent of mantle melting beneath Kamchatka. A parameterized hydrousmeltingmodel [Katz et al. 2003, G3, 4(9), 1073] is utilized to estimate that mantle melting beneath Kamchatka occurs at or below the dry peridotite solidus (1245–1330 °C at 1.5– 2.0 GPa). Relatively high mantle temperatures (yet lower than beneath back-arc basins and ocean ridges) suggest substantial corner flow driven mantle upwelling beneath Kamchatka in agreement with numerical models implying non-isoviscous mantle wedge |
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