Kenzo Yagi

Synthesis of kosmochlor and phase equilibria in the join CaMgSi2O6-NaCrSi2O6

Kosmochlor (NaCrSi2O6) was synthesized by the flux method from melts along the join Na2O·2 SiO2-Na2O·Cr2O3·4 SiO2 at 1000° C in air, and isolated by dissolving the glassy matrix with hydrofluoric and perchloric acids. The join CaMgSi2O6-NaCrSi2O6 was studied at 1 atmosphere in air by the quenching technique at temperatures between 900° and 1450° C, using mixtures of kosmochlor and diopside crystals or diopside glass as starting materials. The phases are diopside solid solution, kosmochlor, spinel (Mg-chromite), eskolaite (Cr2O3) and glass. The maximum solubility of kosmochlor in diopside is 24 wt percent at 1140° C, while diopside is not soluble at all in kosmochlor, resulting in the existence of a wide range of immiscibility. Petrologic significance of the results is discussed.

Aenigmatite, sodic pyroxene, arfvedsonite and associated minerals in syenites from Morotu, Sakhalin

AbstractAenigmatite, sodic pyroxene and arfvedsonite occur as interstitial minerals in metaluminous to weakly peralkaline syenite patches in alkali dolerite, Morotu, Sakhalin. Aenigmatite is zoned from Ca, Al, Fe3+-rich cores to Ti, Na, Mn, Si-rich rims reflecting the main substitutions Fe2+Ti4+⇌Fe3+, NaSi⇌CaAl and Mn2+⇌Fe2+. Aenigmatite replaces aegirine and ilmenite supporting the existence of a ‘no-oxide’ field in

Effect of silica concentration on the diopsidic pyroxenes in the system diopside-CaTiAl2O6SiO2

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Genesis and differentiation of nephelinitic magma

— T space. In one case aenigmatite has apparently formed by reaction between ilmenite and arfvedsonite. Titanian aegirine (up to 3.0 wt% TiO2) and Fe-chlorite may replace aenigmatite. Sodic pyroxene occurs as zoned crystals with cores of aegirine-augite rimmed by aegirine and in turn by pale green aegirine containing 93 mol% NaFe3+Si2O6. Additional substitution of the type NaAl⇌CaFe2+ is indicated by significant amounts (up to 6 mol%) of NaAlSi2O6. Arfvedsonite is zoned with rims enriched in Na, Fe and depleted in Ca which parallels the variation of these elements in the sodic pyroxenes.The high peralkalinity of the residual liquid from which the mafic phases formed resulted from the early crystallization of microperthite (which makes up the bulk of the syenites) leading to an increase in the Na2O/(Na2O+K2O) and (Na2O+K2O)/Al2O3 ratios of the remaining interstitial liquid which is also enriched in Ti, Fe, and Mn. Bulk composition of the melt,

The bearing of the system CaMgSi2O6CaAl2SiO6CaFeAlSiO6 on fassaitic pyroxene

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Crystallization temperature of wyomingite from Leucite Hills

, temperature and volatile content were all important variables in determining the composition and stability of the peralkaline silicates.