Phase equilibria in the system Fe-Ni-S were investigated by dry synthesis at 500°C and 400°C using three elements (Fe, Ni and S) and two synthetic sulfides (FeS and NiS). Phase diagrams of this ternary system at these two temperatures were obtained. The extent of the monosulfide solid solution (mss) is complete at 500°C and 400°C. The d(102)-values of the mss are increasing with the increasing Fe/(Fe+Ni) ratio and are decreasing with the increasing sulfur content of the mss. Pentlandite has the solid solution areas ranging from (Fe0.66Ni0.34)9.02S8.00 to (Fe0.30Ni0.70)9.35S8.00 at 500°C and from (Fe0.70Ni0.30)9.39S8.00 to (Fe0.41Ni0.59)9.24S8.00 at 400°C. Violarite has the solid solution area ranging from (Fe0.16Ni0.84)3.02S4.00 to (Fe0.34Ni0.66)3.00S4.00 at 400°C and does not exist at 500°C. Godlevskite is stable at 400°C and it transforms to α-Ni7S6 phase at 500°C run. Tie lines of pentlandite to godlevskite at 400°C and pentlandite to α-Ni7S6 phase at 500°C are stable. On the Fe-Ni join, two kinds of Fe-Ni alloys (α-iron and γ-phase) and pure nickel are stable. Alfa-iron has a body-centered cubic structure and pure nickel has a face-centered cubic structure. Gamma-phase has a primitive tetragonal structure and the FeNi3 phase is included in the γ-phase solid solution.
Sr, Nd, C and O isotopic compositions were determined for carbonatite and associated peralkaline silicate rocks from the Zhidoy complex in the East Sayan province, Russia. The complex consists predominantly of alkali pyroxenite with a small amount of ijolite, nepheline syenite and carbonatite. Rb-Sr isotopic data for two carbonatite samples, ijolite, and nepheline syenite give a whole rock isochron age of 569 Ma with initial εSr and εNd values of about −6.1 and 1.1, respectively. This indicates that the rocks were derived from a single parental magma by magmatic differentiation. Judging from the mode of occurrence, it is presumed that the carbonatites were produced by carbonate-silicate liquid immiscibility. Another two carbonatite samples have εSr and εNd values of −9.3 and −11.8, 2.3 and 3.4, respectively. They show a wide range of variation in initial εSr and εNd values. The concentration of Sr in the rock varies from 4660 to 13600 ppm. The chemical and isotopic variations in the carbonatite are not due to crustal contamination but are the result of the mixing of two different carbonatitic components. It is concluded that alkaline magmatism occurred at least twice in the Zhidoy area: (1) the first magmatism produced the alkali pyroxenite cumulate and the carbonatite with low initial 87Sr/86Sr ratio; (2) the second one produced the ijolite, nepheline syenite and high-εSr carbonatite. The generation of magmas with different 87Sr/86Sr and 143Nd/144Nd ratios may reflect an isotopic heterogeneity of the mantle source region.
The post-collisional Garam Chashma leucogranite with K-Ar (biotite) ages of 20-18 Ma occurs in the Hindukush Range (Trans-Himalayas), northwestern Pakistan. The leucograntie is per-aluminous and shows a restricted range of SiO2 contents (72-75 wt%). It is different, both in mineralogy and chemical characteristics, from the surrounding pre-collisional granodiorites and post-collisional meta-aluminous to per-aluminous Miocene Baltoro granite from Trans-Himalayas in Northeast Pakistan. The age and chemical trends of Garam Chashma leucogranite are similar to those of the Higher Himalayan granites of Pakistan, India, Nepal and South Tibet, suggesting similar source and/or processes of formation.
Thermal structure deformation of ScAlO3 perovskite was studied by in situ X-ray single crystal structure analysis at high temperatures. As temperature increases, all structure parameters of the orthorhombic perovskite shift very slightly toward the ideal polyhedral symmetries. The cell volume shows a quadratic thermal expansion expressed by V(T)/V293=1+1.151×10−5T+9.218×10−9T2. The expansions of ScO8 and void space are significant for the cell volume expansion because they occupy large volume in the unit cell. The tilting and rotation of AlO6 octahedral linkage are a little changed by the anisotropic thermal motion of O1 and O2. Higher order anisotropic anharmonic thermal parameters of γpqr and δpqrs of O1 and O2 atoms are increased noticeably with temperature. Anharmonic motions of oxygen atoms, inducing the tilting and rotation of AlO6 octahedra mainly control the thermal changes of perovskite structure.