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Magmatic origin of low-Ca olivine in subduction-related magmas: Co-existence of contrasting magmas


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Kamenetsky, VS, Elburg, MA, Arculus, RJ and Thomas, R 2006 , 'Magmatic origin of low-Ca olivine in subduction-related magmas: Co-existence of contrasting magmas' , Chemical Geology, vol. 233, no. 3-4 , pp. 346-357 , doi: 10.1016/j.chemgeo.2006.03.010.

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Unravelling the origin of different components contributing to subduction-related magmas is a prerequisite to understanding the sources and processes involved in their origins. Mafic, high-Ca subduction-related magmas from geographically-diverse areas (Indonesia, Solomon Islands, Kamchatka, Valu Fa Ridge) contain two populations of olivine crystals, of which only the high-Ca population (CaO = 0.3-0.5 wt.%) crystallized from the melt that dominantly contributed to the whole rock composition. Forsterite-rich (Fo90-94), low-Ca (CaO < 0.15 wt.%), high-Ni (NiO > 0.3 wt.%) olivine crystals, which constitute 16-37 vol.% of total olivine population, are generally interpreted as mantle or lithospheric xenocrysts. However, in these samples, the olivine shape and chemical zoning, the composition of included minerals (orthopyroxene, clinoenstatite and Cr-spinel) and presence of melt inclusions, are indications that these crystals are phenocrysts from a mafic magma with high silica and low calcium contents. The coexistence of contrasting magmas (mafic high-Ca silica-poor versus low-Ca silica-rich) within a number of arc systems and their mixing may not be a rare event, and should be taken into account when developing models of arc petrogenesis.

Item Type: Article
Authors/Creators:Kamenetsky, VS and Elburg, MA and Arculus, RJ and Thomas, R
Keywords: Island-arc magmas; Picrites; Olivine; Clinoenstatite; Magmatic inclusions; Xenocrysts; Mantle
Journal or Publication Title: Chemical Geology
DOI / ID Number: 10.1016/j.chemgeo.2006.03.010
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