Solid Solution Field Research Articles

An electron, and X-ray powder, diffraction study of cubic, fluorite-related phases in various ZrO 2 Ln2O 3 systems

A detalied electron, and X-ray powder, diffraction study has been made of the cubic, fluorite-related solid solution fields in a range of ZrO 2 Ln 2O 3 systems. A rich variety of composition-dependent diffraction effects were observed, leading to the realization that it is possible for there to be a much more gradual transition between apparently distinct structural types as a function of composition than was previously thought to be the case. Labels such as F-type (or C 1), C-type (or C 2) or pyrochlore as traditionally used are rather inappropriate and unhelpful when attempting to describe structural variations across and between such solid solution fields.

The ternary system BaO-CaO-CuO-O

Subsolidus equilibrium relationships are determined among the phases of the BaO-CaO-CuO-O system at 900°C in oxygen. Two new ternary compounds are detected: Ba 4CaCu 3O 8.25 (cubic, a O = 8.157 A) and Ba 6CaCu 3O 10.5 (tetragonal, a O = 4.055 A, c O = 21.605 A) while a solid solution field is evidenced as originating from BaCuO 2+δ by the substitution of Ca for Ba up to a limit of about 8 at%. X-ray powder diffraction analysis shows that the above two phases are isostructural with the corresponding ones originating in the basic zone of the system BaO-Y 2O 3-CuO-O with composition Ba 4YCu 3O 9 and Ba 6YCu 3O 11.

A modulation-wave approach to the structural description of the Nb2Zr x –2O2x+1 (x = 7.1–10.3) solid-solution field

La decomposition de Fourier de l'affinement structural de Ealy & Bath pour l'une des compositions, Nb 2 Zr 6 O 17 , conduit aux sous-mailles metalliques (Amma, a M ≃5,1, b M ≃4,9, c M ≃5,2 A) et d'oxygene (Pmam, a 0 =[x/(2x+1)], b 0 =b M , c 0 =c M ), avec des expressions specifiques pour les fonctions de modulation decrivant la deviation des deux sous-reseaux par rapport aux sous-mailles parentes correspondantes. Les conditions d'extinction de la solution solide impliquent une symetrie de groupe de superespace de M: Amma: 1S1

Phase equilibria of the system diopside-acmite at low oxygen fugacity: a preliminary report.

A preliminary study on phase equilibrium relataions in the system diopside (CaMgSi2O6)-acmite (NaFeSi2O6) have been carried out at the oxygen fugacities of 10-8, 10-10, and 10-12 atm. in the temperature range from 1000°C to 1400°C. Fundamental phase relations are similar at each oxygen fugacity. Experimental data suggest that there is a one-phase field of pyroxene solid solution between two end members below 1000°C. The pyroxene solid solutions richer in acmite component than 50 wt.% melt incongruently into magnetite + liquid (10-8 and 10-10 atm fO2) or wustite + liquid (10-12 atm fO2). Pyroxene is a primary phase in the diopside-rich portion and wustite in the acmite-rich portion. Judging from X-ray diffraction data, the clinopyroxene is not a solid solution of diopside and acmite, but contains other component, possibly hedenbergite, at high temperatures and low oxygen fugacities.

Preparation of ductile NbAl powders for the fabrication of Nb 3AI superconductors. II

Small NbAl powder compacts and arc-melted alloys with aluminium contents up to 30 at.% were melted and rapidly quenched from the melt using a modified twin piston and a hammer and anvil technique. At calculated cooling rates between 10 5 and 10 7 K s −1 a metastable extension of the niobium solid solution field up to 27 at.% Al was reproducibly achieved. At slightly higher aluminium concentrations the quenched specimens showed the Nb 3Al phase with the A15 structure. The nucleation of the Nb 2Al phase was suppressed. Ductile NbAl powders of the composition “Nb 3Al” were prepared by application of a combined hydriding-dehydriding process at temperatures lower than 450 °C. The surface quality of the quenched splats essentially influences the hydriding procedure. The retransformation behaviour of the metastable states as a function of content and temperature was investigated. With increasing temperature the Nb 3Al phase precipitates from the strongly supersaturated niobium solid solution. After heat treatme its at temperatures lower than 700 °C formation of the Nb 2Al equilibrium phase could not be observed between 21.5 and 27.5 at.% Al.

Research on the system BaO-La 2O 3-CuO-O 1° the join Ba 2CuO 3+δ — Ba 1.33La 0.67CuO 3+δ

The phases deriving from Ba 2CuO 3+δ by partial substitution of lanthanum for barium atoms up to the limit composition Ba 1.33La 0.67CuO 3+δwere investigated. The reaction environment was CO 2 free air, in order to avoid any pollution of the samples by CO −− 3 ions. At 950°C the system is characterized by the presence of two solid solution fields Ba 2−xLa xCuO 3+δ: the first shows tetragonal structure K 2NiF 4-type with disordered anionic vacancies and stretches from x=0 to x=0.05, the second has an orthorhombic structure deriving from that of Sr 2CuO 3 and extends from x=0.25 to x=0.67. Under 450°C the tetragonal phase disappears and we observe a unique solid solution fields, with orthorhombic symmetry

Stability Fields of Solid Solutions in Phase Diagrams

Projection of Gibbs-free-energy curves is necessary for the graphical derivation of the stability field of a multicomponent solid solution in phase diagrams for soil minerals. The shapes of the projected curves depend on the multicomponent Gibbs function of the solid solution and the values of the fixed chemical potentials. The program XTERN, written in GWBASIC for the PC, calculates projected curves for ternary solid solutions with known Gibbs functions. Parameters of the ternary Redlich-Kister function are used as standard input, but any other ternary function can be used.

Stability of RSiO3 phases in the manganese rich portion of the system MnO-MgO-FeO-SiO2-CO2.

Experimental investigation in the Mn-rich portion of the system MnO–MgO–FeO–SiO2–CO2 has been carried out to study the effect of XFe on the phase relation in the ternary system MnSiO3–MgSiO3–FeSiO3. The experiments were conducted with oxygen and/or graphite buffers in the system C–O–H at pressure-temperature conditions corresponding to normal crustal metamorphism to understand the evolution of mineral assemblages from Ca-poor Mn–Mg–Fe carbonates admixed with silica.Stability field of pyroxmangite solid solution containing Fe can appear at lower temperature than the MnSiO3 end member. The appearance of single phase pyroxmangitess is insensitive to variations in XMn of the bulk in the range ∼0.8 and above. With increasing XMg and XFe in the bulk composition, carbonatess+quartz react to produce pyroxmangitess+Mn-clinopyroxeness and Mn-clinopyroxeness successively. All the reaction boundaries are insensitive to pressure, at least up to 8 kb, and have gentle slope in temperature. These reactions are also independent of the XCO2 of the fluid phase in the region XCO2=0.21−0.53 above moderate temperatures. The slope of the lnXCO2−10−3/T K relationship of these reactions is similar to that of the pure pyroxmangite forming reaction. Mn-clinopyroxeness can be stabilized at a low temperature than pyroxmangitess from favourable bulk composition [X(Mg+Fe)=0.4]. With increasing Fe content, stability field of Mn-clinopyroxeness extends toward higher XMn in region as compared to that in Fe-free system.

Low temperature phase equilibria and ordering in the ZrO2-rich region of the system ZrO2-CaO

From co-precipitated powder samples, the solid state reactions occurring between room temperature and 1500° C in the ZrO2-CaO system have been studied. At low temperatures, compositions containing < 25 mol% CaO show a complex picture of phase transformation and ordering in the system. From the obtained results the following singular reactions have been established. (i) Tetragonal zirconia solid solution decomposes eutectoidally at 7 mol% CaO and 1048 ± 4° C into monoclinic zirconia solid solution and calcium zirconate (CZ). (ii) Cubic zirconia solid solution undergoes a eutectoidal decomposition at 17.5 mol% Cao and 1080 ±20° C into tetragonal solid solution + calcium zirconate. (iii) The monoclinic ordered phase, CaZr4O9 (Φ1), ), undergoes an order-disorder transformation into cubic zirconia solid solution at 1232 ± 5° C. (iv) Cubic zirconia solid solution undergoes a eutectoidal decomposition into two ordered phases, Φ1 + Φ2 at 21 mol% CaO and 1200 ± 10°C. (v) Hexagonal ordered phase Ca6Zr19O44 (Φ2) decomposes peritectoidally into cubic zirconia solid solution + calcium zirconate at 1360 ± 10° C. The two ordered phases Φ1 and Φ2 seem to be unstable below ≈ 1100° C. By using DTA, X-ray diffraction and SEM techniques, the extent of the tetragonal and cubic zirconia solid solution fields have been established. From the above experimental results a new tentative phase diagram is given for the ZrO2-rich region of the system, ZrO2-CaO.

Systematics of chlorite alteration at the Phelps Dodge massive sulfide deposit, Matagami, Quebec

Hydrothermal alteration at the Phelps Dodge Archcan volcanogenic massive sulfide deposit has converted rhyodacite and rhyolite footwall rocks into the following mineral assemblages: quartz-chlorite-albite-epidote + or - sericite, quartz-chlorite + or - sericite, chlorite + or - sericite, and chlorite-talc + or - stilpnomelane. Alteration at constant Al was initiated by hydration, addition of Fe + Mg, silicification, and leaching of Ca + Na which produced Al-saturated chlorites with a wide range of Fe/Fe + Mg ratios within the assemblage quartz-chlorite-albite-epidote + or - sericite. With continued addition of Fe and less Mg, combined with extensive leaching of quartz, the chlorite became Al-undersaturated (quartz-chlorite-talc assemblage), and ultimately formed a rock composed essentially of chlorite. The chlorite-talc + or - stilpnomelane assemblage is stable in late crosscutting veinlets and in the ore zone.Chlorites in the Si-Al-Mg-Fe system form a rectangular solid solution plane with limited substitution of Al for Si and extensive substitution of Fe for Mg. In Si-Al space the solid solution plane is outlined by Al saturation (presence of other Al-rich mineral) and Al undersaturation (presence of Al-poor or Al-free mineral) boundaries. Al iv substitution for Si in the chlorites increases from 2.3 to 3.01 formula units (based on 8 Si + Al iv ) with Fe/Fe + Mg, whereas Al iv occupancy decreases from 2.88 to 2.65. The valence charge balance is compensated by octahedral site vacancies or by the conversion of Fe (super +2) to Fe (super +3) . The Al iv content of chlorite also increases with temperature. Chlorites on the Al-saturated boundary of the solid solution field form a potentially useful geothermometer: T degrees C = 106 Al iv + 18; Al iv is corrected for changes with the Fe/Fe + Mg ratio as: Al iv corrected = Al iv + 0.7 Fe/Fe + Mg.The Fe/Fe + Mg ratios of bulk rock and contained chlorite correlate well. Birefringence colors of the chlorite change from green to brown, violet, and Berlin Blue as Fe/Fe + Mg changes from 0.18 to 0.64. The Fe/Fe + Mg variation apparently depends largely on the proportions of Mg-rich seawater and Fe-rich hydrothermal fluid in the altering brine.

Phase Relations and Ordering in the System ZrO2‐MgO

The Phase relationships in the system ZrO2‐MgO were reinvestigated over a wide range of temperatures and compositions. The extent of the cubic solid solution field was determined with precise lattice parameter measurements and a high‐temperature X‐ray furnace using analyzed samples. DTA results show that the addition of MgO to ZrO2 decreases the transition temperature for monoclinic ⇌ tetragonal ZrO2 and 1 mol% of MgO is soluble in the monoclinic zirconia at ∼1070°C.The invariant eutectiod point is at 13.5 ± 0.3 mol% MgO at 1406°± 7°C, which is in fair agreement with previous results by Grain. The ordered phase Mg2Zr5O12 (δ‐phase) can form metastably in cubic solid solutions at temperatures as low as 800°C after prolonged annealing. Evidence for the existence of the ordered phase MgZr6O13(γ‐phase) was obtained by electron diffraction technique. Conditions for the formation of this phase are described. The ordered phases in this system are metastable and their formation is an intermediate step in the eutectoid decomposition of the cubic phase.

Ductile/brittle grain-boundary fracture behaviour of L12-type intermetallic compounds

The fracture behaviour of grain boundaries in L12-type intermetallic compounds was investigated to explain recent experimental results reported by Takasugiet al. and Inoueet al. Inspection of these results revealed a simple rule; grain boundaries are ductile in Kurnakov compounds having an order-disorder transition below their melting point and a wide solid-solution field. On the other hand, grain boundaries are brittle in Berthollide compounds having no order-disorder transition below their melting point. The ductile grain-boundary behaviour in Kurnakov compounds is considered to be produced by disordered grain boundaries, intrinsically ductile and inherited when formed in disordered states.

Phase Relations on the Actinolite-Pargasite Join

Phase relations along the join Ca2Mg4Fe2+Si8O22 (OH)2 (Actinolite)-NaCa2Mg3·2Fe0·82+AlSi6 Al2O22(OH)2 (Pargasite) have been studied at PH2O = 1 kb and the oxygen fugacities defined by the iron-wustite(IW) buffer. Actinolite and bornblende are separated by a solvus and the field of actinolite+hornblende+vapor is present in the region between Ac85Pa15 and Ac55 Pa45 at 680 °C. Complete miscibility is achieved at 720 °C. At temperatures higher than the solvus there is a continuous solid solution series between the two end members. The stability field of amphibole solid solution gradually increases with increasing pargasite content in actinolite. The phase assemblages at temperatures higher than those of a solid solution series between the two end members change with increasing pargasite content in the bulk composition as follows; Act+Cpx+Qz+V, ActHbl+Cpx+Opx+Qz+V, Hbl+Cpx+Opx+Pl+V and Hbl+Cpx+Pl+Ol+V. In comparison with the Fe-free system, the extent of the miscibility gap between actinolite and hornblende is reduced by an increase in the Fe2+ content. The present study should provide an adequate basis for the interpretation of actinolite-hornblende pairs in metamorphic rocks.

Stability of pentlandite in the Fe-Ni-Co-S system

Pentlandite has a wide compositional range in the Fe-Ni-Co-S system and the Fe-Ni-S system. The metal : sulfur atomic ratio is approximately 9 : 8. The Co content of pentlandite from the Kamaishi ore deposit and one from the Outokumpu ore deposit (Knop et al. 1965) varies from a Co-free to nearly a Co9S8 composition. Pentlandite forms a complete solid solution between (Fe, Ni)9±xS8 and Co9±xS8 in the 600°–300°C temperature range. On the other hand, it is presumed that the pentlandite solid solution decomposes into two fields toward the (Fe, Ni)9S8 and Co9S8 members at 200°C. The field of solid solution at 500°C is the most extensive and includes all of the other solid-solution fields. The metal : sulfur ratio of the solid solution varies systematically, i.e., the Fe-rich field sinks toward the Fe-Ni-Co plane away from the M9S8 section, and contrarily the Ni-rich field shifts toward the sulfur apex. The d044 value decreases with increasing S, Ni, or Co contents in pentlandite. The Kamaishi pentlandites, Iwate Prefecture, Japan, lie within or close to the solid-solution field at 300°C, showing a very good correlation with the Co : Ni ratio of the homogeneous natural pyrrhotite phase.

Muscovite solid solutions in the system K2O-MgO-FeO-Al2O3-SiO2-H2O: an experimental study at 2 kbarPH2Oand comparison with natural Li-Free white micas

AbstractThis paper presents the results of an experimental study of muscovite solid solutions in the system K2O-M2+O-Al2O3-SiO2-H2O-(HF), withM2+= Mg2+or Fe2+in the temperature range 300-700°C under 2 kbarPH2O. Muscovite solid solutions can be described, in this system, as the result of two substitutions. One is the phengitic substitution (x), which preserves the pure dioctahedral character of the mica; the second is the biotitic substitution (y), which leads to trioctahedral micas and does not change the composition of the tetrahedral layer Si3Al. The general formula of muscovite in this system is K(Al2−x−2y∕3M2+x+y□1−y∕3)(Si3+xAl1−x)O10(OH,F)2. Both substitutionsxandyare more extensive at lower temperatures. The extent of solid solution decreases drastically with increasing temperature.ForT&gt; 600°C, the phengitic substitution (x) becomes negligible, but some biotitic substitution (y) persists. This unsymmetrical decrease of the solid solution of muscovite with increasing temperature is similar to that previously observed in phlogopite, the micas with a tetrahedral layer composition of Si3Al being the most stable. The behaviour of muscovite solid solutions in the ferrous system is qualitatively identical to that observed in the magnesian one, but the extent of solid solution is smaller than with Mg2+. Fluorine neither changes the size nor the shape of the solid solution fields but increases their stability by about 50°C.A comparison of these experimental results with data on natural muscovites is presented. Most natural primary (magmatic) granitic muscovites lie very close to the muscovite end member, in agreement with their high-temperature origin. Low-temperature muscovites (300–400°C), typically muscovites from hydrothermally altered granitic rocks, can have highxandyvalues. The rate of the biotitic substitutionycan reach 0.6, which corresponds to an octahedral occupancy of 2.2 atoms per formula unit (based on 11 oxygens), consistent with the experimental data.

Tin in volcanogenic massive sulfide deposits; an example from the Geco Mine, Manitouwadge District, Ontario, Canada

Tin and tin-bearing minerals are prominent in the metamorphosed (amphibolite-granulite facies) Geco Cu-Zn volcanogenic massive sulfide deposit as well as in some of the smaller massive sulfides in the Manitouwadge district. Cassiterite and minor Sn-bearing andradite, epidote, rutile, and phlogopite occur within the massive sulfide ores. Nigerite-24R of composition (Sn, Ti) x (Zn, Mg, Fe, Mn) (sub 8-2x) (Al, Fe) 16 O 32 , with x [asymp] 2, and mixed polytypes of hoegbomite with the general formula (Ti, Sn) x (Fe, Mg, Zn, Mn) (sub 8-2x) (Al, Fe) 16 O 32 , with x [asymp] 1, occur in the footwall rocks which comprise the feeder zone. Hoegbomite is the primary tin-bearing mineral in the districtwide cordierite-gedrite gneisses which represent footwall conformable alteration zones.A relatively high f (sub O 2 ) during metamorphism and also during the formation of the ores accounts for the presence of cassiterite rather than stannite or the simple tin sulfides in the ores. Nigerite and hoegbomite occur only in Ca-Na-deficient Mg-Fe-rich aluminous rocks and are associated with Zn staurolite, corundum, cordierite, sillimanite, (Zn, Fe) spinels, and Fe-Ti oxides.Bulk-rock tin assays systematically increase as the Geco orebody is approached: districtwide cordierite-gedrite gneisses (10-30 ppm), feeder zone (50-330 ppm), and orebody (100-3,000 ppm). Hanging-wall felsic gneisses and nearby mafic gneisses and granites contain less than 3 ppm tin. Small nearby pegmatites contain 2 to 10 ppm tin.From textural evidence, phase equilibria calculations, and the lithologic distribution of tin, a model for the Geco deposit is developed in which the districtwide cordierite-gedrite gneisses represent one segment of the fossil hydrothermal system and in which Cu-Zn and Sn mineralizations are closely associated. Nigerite, hoegbomite, and spinel from Geco occupy distinct and characteristic (Zn, Fe, Mg, Mn) solid solution fields. Hence, these species, which are known to occur as detrital heavy minerals may be useful pathfinders in geochemical exploration for eroded volcanogenic massive sulfide deposits.

Phase relations in the Cu-Fe-Zn-S system between 500 degrees and 300 degrees C under hydrothermal conditions

Phase relations in the Cu-Fe-Zn-S system were studied between 500 degrees and 300 degrees C using both the thermal gradient transport method and the isothermal in situ recrystallization method under hydrothermal conditions. In addition, the compositional fields of chalcopyrite, intermediate solid solution (iss), and sphalerite were determined at temperatures between 500 degrees and 300 degrees C.The stable univariant phase assemblages in the central portion of the system at both 500 degrees and 400 degrees C are covellite + nukundamite + pyrite + sphalerite, covellite + bornite + nukundamite + sphalerite, bornite + nukundamite + pyrite + sphalerite, bornite + chalcopyrite + pyrite + sphalerite, bornite + chalcopyrite + iss + sphalerite, chalcopyrite + iss + pyrite + sphalerite, and iss + pyrite + pyrrhotite + sphalerite. At 300 degrees C stable assemblages of chalcopyrite + pyrite + pyrrhotite + sphalerite and chalcopyrite + iss + pyrrhotite + sphalerite appear in place of the last two assemblages at 500 degrees and 400 degrees C because of a tie line between chalcopyrite and pyrrhotite. Also, a stable tie line between bornite and pyrite commonly found in natural ores occurs in the present system instead of the tie line between nukundamite and chalcopyrite observed in the Cu-Fe-S system.Chalcopyrite has a very small solid solution field close to the stoichiometric CuFeS 2 and dissolves small amounts of zinc (<0.9 at. %) at all three temperatures. Intermediate solid solution has an extensive solid solution field which dissolves up to 3.3 at. percent at 500 degrees C and 1.2 at. percent at 300 degrees C, with a slight reduction in solubility due to pressure. The solid solution area of intermediate solid solution becomes narrower as the temperature decreases and becomes richer in copper with increasing pressure as shown in the system Cu-Fe-S by Sugaki et al. (1982). Sphalerite solid solution dissolves a maximum of about 2.4 mole percent CuS at the three temperatures and has no relation to FeS content and sulfur fugacity.

Phase equilibria and ordering in the system HfO2-Yb2O3

The system HfO2-Yb2O3 was investigated in the 0 to 100 mol % Yb2O3 range using X-ray diffraction analysis, linear thermal expansion measurements and melting point studies. At high temperatures, the system is dominated by wide regions of solid solutions based on HfO2 and Yb2O3 separated by a two-phase field which appears to extend to the solidus. The extent of the cubic hafnia and ytterbia C-type solid solution fields was established using the precision lattice parameter method. At low temperature (< 1800° C) two ordered phases were found in the system, one at 40 mol % ytterbia with ideal formula Yb4Hf3O12, and another at ∼ 70 mol % ytterbia with formula Yb6HfO11. Four eutectoid reactions and a peritectic reaction cubic ytterbia solid solution → cubic hafnia solid solution + liquid at ∼ 67 mol % and ∼ 2380° C have been established in the system. By incorporating the known tetragonal-cubic hafnia and C-type-hexagonal ytterbia transition temperatures, and the melting points data in the system, a tentative phase diagram is given for the system HfO2-Yb2O3.

Katoite, a new member of the Ca3Al2(SiO4)3-Ca3Al2(OH)12 series and a new nomenclature for the hydrogrossular group of minerals

The new mineral katoite, Ca3Al2(SiO4)(OH)8, occurs in Pietramassa near Montalto di Castro (Viterbo, Italy), associated with many other hydrated calcium silicates and aluminates in the vugs of a phonolite which effused through argillaceous marls of Pliocene age. Microprobe and TG analyses yielded the empirical formula Ca2.96(Al1.85Mg0.01)(Si0.69S0.11)O2.93(OH)9.07 ; X-ray study showed it to be cubic, Ia3d with a 12.358(2) Å. Physical properties (thermal behaviour, refractive index, infrared spectrum, and X-ray powder diffraction) are consistent with its chemical composition and with its pertinence to the solid solution series Ca3Al2Si3O12 (grossular) and Ca3Al2(OH)]2 (synthetic phase) with an approximate content of 27 % of the former and 73 % of the latter. This makes it the first natural compound of the series with a grossular content lower than 50 % and confirms the existence, also in nature, of a complete series with a SiO4 ⇌ (OH)4 isomorphous replacement within the grossular structure. By analogy with other isomorphous mineral series, two names, hibschite and katoite, are appropriate to represent the two solid solution fields with more and less than 50 % Si in the tetrahedra, respectively. The name hydrogrossular remains applicable as a group name for members of the whole series with an appreciable OH content but otherwise undetermined SiO4/(OH)4 ratio. The paragenetic sequence found in nature and laboratory experiments reported in earlier literature, indicate for katoite a crystallization temperature of approximately 300 °C with a relatively high water vapour pressure and a limited Si supply.

Phase relations in the central portion of the Cu-Fe-Zn-S system between 800.DEG. and 500.DEG.C.

Phase equilibrium in the central portion of the Cu–Fe–Zn–S system was studied by the evacuated silica glass tube method, and phase relations involving chalcopyrite, intermediate solid solution(iss), bornite, pyrrhotite and sphalerite have been determined between 800° and 500°C. Besides, compositional fields of each solid solution have been clarified. Chalcopyrite appearing only in experiments at 500°C has very limited solid solution field close to the stoichiometric CuFeS2, and dissolves small amounts of zinc less than 0.9 atm.%. However, iss having an extensive solid solution field dissolves considerable amounts of zinc from 12.7 atm.% at 800°C to 3.3 atm.% at 500°C, and these maximum solubilities of zinc are observed in more iron-rich iss than the cubanite composition at each temperature. Meanwhile, sphalerite solid solution also dissolves considerable amount of copper, and the CuS content in sphalerite increases with that of FeS in sphalerite above 600°C. The maximum observed CuS contents are 10.7 mole % at 800°C, 8.6 mole % at 700°C and 4.6 mole % at 600°C in sphalerite containing higher FeS than 40 mole %. Therefore, entry of copper into sphalerite is dependent upon both temperature and sulfur fugacity.