Primitive magmas in the Emeishan Large Igneous Province, southwestern China and northern Vietnam
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Hanski, E and Kamenetsky, VS and Luo, ZY and Xu, YG and Kuzmin, DV, Primitive magmas in the Emeishan Large Igneous Province, southwestern China and northern Vietnam, Lithos: An International Journal of Mineralogy, Petrology, and Geochemistry, 119, (1-2) pp. 75-90. ISSN 0024-4937 (2010) [Refereed Article]
There are several places in the Emeishan Large Igneous Province (ELIP) where highly magnesian volcanic or intrusive rocks accompany more abundant flood basalts. The high-Mg rocks vary in composition from LREE-depleted, low-Ti komatiites to LREE-enriched, high-Ti picrites. These magmas carried cognate olivine phenocrysts with Fo content higher than 91mol% indicating that these olivines crystallized and equilibrated with high-Mg melts. The maximum measured Fo content from the Dali area is 93.5mol% which, depending on the K D value used, indicates a MgO content of 23-25wt.% for the parental melt. The high estimated MgO wt.% values provide evidence for a hot portion of the Emeishan mantle-plume head with a potential mantle temperature of ca. 1700°C. Melt inclusions trapped within olivine phenocrysts have compositions similar to those of the host lavas but with a higher variability in the abundance of incompatible trace elements. The inclusions yield a calculated maximum MgO content of ca. 22wt.% for the melt. The compositional and isotopic variability of the high-Mg magmas in the ELIP is akin to that observed in basaltic rocks, which are divided into low-Ti and high-Ti types, suggesting that most of the basalts were developed in deep crustal magma chambers by fractional crystallization and mixing processes from primitive magmas. © 2010 Elsevier B.V.
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