Arashi Kitakaze

Solubility of sphalerite in aqueous sulfide solutions at temperatures between 25 and 240°c

Abstract In order to assess the role of zinc sulfide complexes in ore-forming solutions, the solubility of sphalerite was measured in NaOHH 2 S aqueous solutions of 0.0 to 3.0 m NaHS concentration at temperatures of 25 to 240°C. Solubilities vary with temperature, activities of H 2 S(aq) and HS − , total reduced sulfur concentration (∑S), and pH. From the solubility data, the main reactions that form zinc sulfide complexes were determined as follows: ZnS ( s ) + H 2 S ( aq ) = Zn ( HS ) 2 0 , ZnS ( s ) + H 2 S ( aq ) + HS − = Zn ( HS ) − 3 , ZnS ( s ) + H 2 S ( aq ) + 2 HS − = Zn ( HS ) 4 2− , ZnS ( s ) + H 2 O (1) + HS − = Zn ( OH )( HS ) − 2 , and ZnS ( s ) + H 2 O (1) + 2 HS − = Zn ( OH )( HS ) 2− 3 . Their equilibrium constants (log K ) are 25°C: −5.3, −3.3, −3.4, −4.4, −4.9; 100°C: −5.2, −3.5, −3.2, −4.1, −5.0; 150°C: −4.7, −3.8, −3.1, −4.7, −5.2; 200°C: −5.1, −3.4, −3.1, −4.6; 240°C: −4.9, −3.3, −3.1, −4.9, respectively. Zn(OHXHS) 2− 3 is not stable at temperatures higher than 200°C. Zinc sulfide complexes predominate over chloride complexes in relatively low temperature hydrothermal solutions which have high ∑S, low ∑C1 − , and high pH values. In these solutions, ZnS is precipitated in response to changes of temperature, pH, and ∑S. Among them, decrease of ∑S is more effective than that of temperature and pH. Zinc sulfide complexes do not transport significant zinc in those ore-forming solutions responsible for economic zinc sulfide deposits. However, they become predominant zinc species in certain geothermal solutions and ore-forming solutions responsible for some epithermal precious metal deposits.

New phase relations in the Cu-Fe-S system at 800 °C; constraint of fractional crystallization of a sulfide liquid

Phase equilibrium in the Cu-Fe-S system has been investigated for over 100 samples by the sealed silica tube method at 800 °C. Bornite shows solid solutions ranging from (Cu 4 . 7 0 Fe 1 . 3 0 ) 6 . 0 0 S 4 . 0 0 to (Cu 7 . 4 3 Fe 0 . 0 0 ) 7 . 4 3 S 4 . 0 0 , and those of pyrrhotite ranges from (Cu 0 . 0 4 Fe 1 . 0 1 ) 1 . 0 5 S 1 . 0 0 to (Cu 0 . 0 0 Fe 1 . 0 0 ) 1 . 0 0 S 1 . 0 0 . The intermediate solid solution (iss) and the sulfide liquid exist in the central part of this system. The most important difference between the phase diagram obtained in this study with that reported by KULLERUD et al. (1969) is that the sulfide liquid is between bornite and pyrrhotite, and that the tie-lines between bornite and iss and between bornite and pyrrhotite are unstable. The new phase diagram of this system at 800 °C is reported.

Triclinic liddicoatite and elbaite in growth sectors of tourmaline from Madagascar

Abstract Crystals of liddicoatite-elbaite tourmaline from a pegmatite in Jochy, Madagascar are composed of o{021̄1}, r{101̄1}, c{0001}, a{112̄̄0}, and m{101̄0} sectors, which correspond to the prominent crystal faces, respectively. Therefore, the sectors were produced during growth, not by strain after growth. The o, m, and r sectors of one specimen are biaxial between crossed polars [2V(-) = 30°, 20°, and 15°, respectively] and triclinic, as indicated by X-ray diffraction. The a sector is optically biaxial and orthorhombic. The c sector is optically uniaxial and essentially trigonal as indicated by single-crystal X-ray diffraction. The o, r, and c sectors are of liddicoatite component, whereas the a sector of the one specimen corresponds to fluor-elbaite. Another crystal specimen comprises a and m sectors, which are polysynthetically twinned, resulting in striations parallel to the c axis on the prism faces, and of liddicoatite. All five sectors have vacancies in the X-site (Ca, Na, ⃞ ).

A re-examination of herzenbergite–teallite solid solution at temperatures between 300 and 700°C

Abstract In order to investigate the range of the solid solution series in herzenbergite-teallite minerals, samples of different composition were synthesized. Herzenbergite-teallite minerals were synthesized by an evacuated silica glass tube method at 700°C. A linear relationship between cell dimensions, a, b and c and composition is established. Extension of solid solution to the Pb-rich portion of the system PbS-SnS is limited; the solid solution area is between Pb1.060Sn0.940S2 and SnS at 700°C. Teallite coexisting with galena was also synthesized by hydrothermal recrystallization at 300, 400 and 450°C. The compositions of teallite are Pb1.140Sn0.860S2 at 300°C, Pb1.114Sn0.886S2 at 400°C, and Pb1.124Sn0.876S2 at 450°C, respectively. Their compositions shift towards the PbS end-member from stoichiometric teallite. The cell dimensions of teallite, which was synthesized hydrothermally, follow the linear relationship between cell dimensions and composition established at 700°C.

Growth and Characterization of Silver Thiogallate (AgGaS2) Crystals by the Hydrothermal Method

A silver thiogallate (AgGaS2) crystal has been successfully grown by a hydrothermal method in order to avoid the occurrence of the exsolution texture in a grown crystal which leads to the lowering of the optical transparency in a wide range. The characterization of grown crystal is also investigated, and compared with the crystal grown by Bridgman method.

Cell Parameters Refinment Using Guinier Method.

The accurate X-ray powder data were obtained by a Guinier focusing camera method using monochromatized Xray radiation. The intensities and angles of X-ray diffractions on the Guinier film were measured by automated microphotomete rcontrolled by a personal computer. X-ray diffraction data were obtained by profile fitting employing an asymmetric pseudo-Voigt function of split type using non-linear least squares calculation. Using these data, the relative errors of the cell parameters were estimated to be less than 5·10-5.