Mineralogical Study of Interstitial Phase Assemblages in Titaniferous Peridotite Xenoliths from Pliocene Basanites of Vitim Volcanic Field (Transbaikalia, Russia)

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Origin of microlite assemblages in Ti-rich peridotite xenoliths from basanite of Dzilinda River (Vitim volcanic field) is discussed. Major minerals in the melt pockets are olivine, clinopyroxene, Cr-spinel, rutile, plagioclase, and sanidine. Rarely ilmenite, armalcolite, loveringite, apatite, and goethite are also observed. Ni-bearing sulfide inclusions form chains in the primary minerals and coexist with amphibole and goethite. Studied melt pockets are most likely represent products of a reaction of primary minerals with small melt fraction during transport to the surface of shortly before entrainment. Occurrence of abundant Ti-oxide minerals may reflect primary mineralogy of Ti-rich peridotite. The coarse rutile grains can be primary in the xenoliths and could be formed long before transport of xenoliths to the surface. Sulfides in Dzhilinda xenoliths form chains together with pseudosecondary fluid and recrystallized glass inclusions and are not related to interstitial assemblages. Pentlandite and monosulfide solid solution represent product of crystallization of immiscible sulfide melt in the mantle. Viterite can be formed by alteration of pentlandite. Rounded goethite inclusions may represent pseudomorphs on sulfide. This is supported by presence of amphibole in the inclusions (which provide water for goethite) and high CuO content of goethite.論文Article
東北大学の論文
2006-03-30