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The Fe−Ni−S system above 700°C (Iron−Nickel−Sulfur)
... The appearance of high-form pentlandite b 1 solidsolution and b 2 as stable phases required the reexamination and revision of the phase diagrams of the system Fe-Ni-S above 650 8C as shown by previous authors (Kullerud 1963b, Kullerud et al. 1969, Hsieh et al. 1982, Baker 1983, Hayashi 1985, Fedorova & Sinyakova 1993, Karup-Møller & Makovicky 1995, Peregoedova & Ohnensetter 2002. Thus, we investigated the isotherms at temperatures from 875 to 650 8C. ...
... No phase corresponding to high-form pentlandite solid solution including Fe 4.5 Ni 4.5 S 8.0 was found at temperatures above 610 8C by Kullerud (1963a, b), Kullerud et al. (1969), or Hsieh et al. (1982. However, Sugaki et al. (1983Sugaki et al. ( , 1984 found an extensive field for high-form pentlandite with more Fe-rich compositions than Fe 4.5 Ni 4.5 S 8.0 to Ni 36x S 2 FIG. 6. ...
... phase b with a limited solid-solution at 850 8C was also described by Hsieh et al. (1982). However, these phases are located in the liquid field or along its S-rich boundary at 850 8C in this study, except for a small Srich part of phase b. ...
An elongate field of high-form pentlandite solid-solution, Fe 5.65Ni 3.35S 7.85, β 2 (Ni 4±xS 3), occurs in the system Fe-Ni-S at 650°C. This solid solution coexists with monosulfide solid-solution, β 1 (Ni,Fe)3±xS2 and g (Fe,Ni). Pentlandite with a composition Fe5.60Ni3.40S7.82 first appears as a stable phase at 625°C owing to the phase transition of the most Fe-rich high-form pentlandite with the same composition. It grows as a limited solid-solution, from Fe5.64Ni3.36S7.82 to Fe3.25Ni5.75S7.92 at 600°C and from Fe5.68Ni3.32S7.85 to Fe2.43Ni6.57S7.85 at 500°C owing to a continuous phase-transition, exsolution and breakdown (pseudoperitectoid and pseudo-eutectoid) of the high-form solid-solution and the exsolution and breakdown (pseudo-eutectoid) of b1. The compositional range of the solid solution is also increased by the exsolution of monosulfide solid-solution below 625°C. Pentlandite coexists with high-form pentlandite (625° to 503°C), monosulfide solid-solution (below 625°C), g (below 617°C) and b1 (579° to 484°C). High-form pentlandite still remains stable below 520°C, but breaks down to pentlandite, high-form godlevskite and b1 at 503° ± 3°C and Fe1.04Ni7.96S6.93 (eutectoid). Phase b1 also breaks down to pentlandite, heazlewoodite and g at 484° ± 3°C and Fe0.26Ni2.87S2.00 (eutectoid). The assemblages with pentlandite and high-form godlevskite or heazlewoodite first appear at 568° ± 3°C or 498° ± 3°C, respectively. In this study, we show that pentlandite in the Ni-Cu ores can form at temperatures from 625° to 500°C or less owing to the phase transition, exsolution and eutectoid of the high-form pentlandite solid-solution, monosulfide solid-solution and b1. These are the primary phases that would crystallize from sulfide magma (liquid in the system Fe-Ni-S) between around 1000° and 750°C.
... ) reported that pentlandite Fe 4.5 Ni 4.5 S 8 is present as a stable phase below 610 C, but breaks down into a mixture of Ni 3 x S 2 and pyrrhotite (monosulfide solid solution) at this temperature or above. However Sugaki et al. (1982) and Sugaki and Kitakaze (1992) found instead that pentlandite transforms into a high form at 610 C that is stable up to 865 C. The existence of a high-form pentlandite as the stable phase required the reexamination and revision of the Fe-Ni-S phase diagrams above 600 C, especially in the central portion of the system, given by Kullerud (1963b), Kullerud et al. (1969), and Hsieh et al. (1982). Sugaki et al. (1984 Rosenqvist 1954;Kullerud and Yund 1962) in the Ni-S join at 800 and 650 C, respectively. ...
... As mentioned above, the thermal stability range of pentlandite including its high form in fact extends up to 865 C, approximately 255 C higher than 610 C suggested by Kullerud (1962Kullerud ( , 1963a). The phase diagram of the Fe-Ni-S system at temperatures above 600 C by Kullerud (1963b), Kullerud et al. (1969), and Hsieh et al. (1982 should now be re-appraised because the high form of pentlandite was not previously identified, although they did report a ternary phase (Ni,Fe) 3x S 2 near the NiS join at 860 ( Kullerud 1963b) and 850 C ( Hsieh et al. 1982). The high form of pentlandite has a SS with a limited range from Fig. 6). ...
... As mentioned above, the thermal stability range of pentlandite including its high form in fact extends up to 865 C, approximately 255 C higher than 610 C suggested by Kullerud (1962Kullerud ( , 1963a). The phase diagram of the Fe-Ni-S system at temperatures above 600 C by Kullerud (1963b), Kullerud et al. (1969), and Hsieh et al. (1982 should now be re-appraised because the high form of pentlandite was not previously identified, although they did report a ternary phase (Ni,Fe) 3x S 2 near the NiS join at 860 ( Kullerud 1963b) and 850 C ( Hsieh et al. 1982). The high form of pentlandite has a SS with a limited range from Fig. 6). ...
The high-temperature form of pentlandite (Fe 4.5 Ni 4.5 S 8) was found to be stable between 584 3 and 865 3 C, breaking down into monosulfide solid solution and liquid at the later temperature. The phase is unquenchable and always displays the X-ray pattern of pentlandite (low form) at room temperature. High-temperature X-ray diffraction demon-strated that the high form has a primitive cubic cell with a 5.189 Å (620 C) corre-sponding to a/2 of pentlandite. The high-low inversion is reversible, accompanied by a large latent heat. It is thought to be order-disorder in character. The transition temperature falls with decreasing S content. The high form of pentlandite has a limited solid solution from Fe 5.07 Ni 3.93 S 7.85 to Fe 3.61 Ni 5.39 S 7.85 at 850 C. However its solid solution extends rapidly toward Ni 3 X S 2 in the Ni-S join with decreasing temperature. High-form pentlandite with Fe Ni in atomic percent crystallizes first by a pseudoperitectic reaction between mon-osulfide solid solution and liquid. The high form (Fe Ni) crystallized from the liquid always has the metal-rich (S-poor) composition in the solid solution at each temperature and coexists with taenite (Fe,Ni) below 746 3 C. This metal-rich high-form Fe 4.5 Ni 4.5 S 7.4 breaks down into pentlandite and (Fe,Ni) at 584 3 C (pseudoeutectoid). These results suggest that in geological processes, such as the formation of Ni-Cu ore deposits, pentlandite can crystallize as the high form from liquid (sulfide magma) at the comparatively high temperatures around 800 C.
... Simulated microcratering experiments on aqueously altered carbonaceous chondrites and reference phyllosilicates using nanosecond and femtosecond pulsed lasers described the formation of identical vesiculated structures, trapped within a melted layer of silicate material (Thompson et al. 2020;Hallatt et al. 2022). Additionally, the melt layers contain numerous rounded nanosulfides (Figure 2) finely dispersed in the silicate glass and even sometimes concentrated at the interface with the phyllosilicate matrix, hinting to the possibility of locally reaching temperatures above 1200°C, the melting point of iron sulfides (Hsieh et al. 1982). This scenario led to the formation of a silicate-sulfides emulsion. ...
Airless bodies are subjected to space-weathering effects that modify the first few microns of their surface. Therefore, understanding their impact on the optical properties of asteroids is key to the interpretation of their color variability and infrared reflectance observations. The recent Hayabusa2 sample return mission to asteroid Ryugu offers the first opportunity to study these effects, in the case of the most abundant spectral type among the main-asteroid belt, C-type objects. This study employs vibrational electron energy-loss spectroscopy in the transmission electron microscope to achieve the spatial resolution required to measure the distinct mid-infrared spectral signature of Ryugu's space-weathered surface. The comparison with the spectrum of the pristine underlying matrix reveals the loss of structural -OH and C-rich components in the space-weathered layers, providing direct experimental evidence that exposure to the space environment tends to mask the optical signatures of phyllosilicates and carbonaceous matter. Our findings should contribute to rectifying potential underestimations of water and carbon content of C-type asteroids when studied through remote sensing with new-generation telescopes.
... In order to see if sulfide liquids are more stable than the predicted assemblages, the relative atom proportions of Fe and S were calculated for the metallic nickel-iron + pyrrhotite assemblage predicted at each temperature step for dust enrichments of 500x, 800x and 1000x at 10 -3 bar, and are plotted on a portion of the liquid-crystal phase relations in the Fe-S binary (Chuang et al., 1986a) in Fig. 15. The dashed curves in this figure are the phase boundaries that result from addition of 7% Ni to the system, taken from the work of Hsieh et al. (1982), projected onto the Fe-S plane. Under all conditions, the trajectory of the condensate compositions initially falls vertically along the left margin of the diagram until the temperature of pyrrhotite formation is reached. ...
Full chemical equilibrium calculations of the sequence of condensation of the elements from cosmic gases made by total vaporization of dust-enriched systems were performed to investigate the oxidation state of the resulting condensates. Computations included 23 elements and 374 gas species over a range of -3=log10(total P) to -6 bar and for enrichments to 1000x in dust of C1 chondritic composition relative to a system of solar composition. Because liquids are stable condensates in these systems, the MELTS non-ideal solution model for silicate liquids was used. Condensation at logP=-3 bar and dust enrichments of 100x, 500x and 1000x occurs at oxygen fugacities of IW-3.1, IW-1.7 and IW-1.2, respectively, and, at the temperature of cessation of direct condensation of olivine from the vapor, yields X(fayalite) of 0.019, 0.088 and 0.164, respectively. Silicate liquid is a stable condensate at dust enrichments >~12.5x at logP=-3. At 1000x, the Na and K oxide contents of the last liquid reach 10.1 and 1.3 wt%, respectively, at logP=-3 bar. At logP=-3 bar, iron sulfide liquids are stable condensates at dust enrichments at least as low as 500x, and the predicted distribution of Fe between metal, silicate and sulfide at 1310K and a dust enrichment of 560x matches that found in H chondrites, and at 1330K and 675x matches that of L chondrites prior to metal loss. With some exceptions, many chondrule glass compositions fall along bulk composition trajectories for liquids in equilibrium with cosmic gases at logP=-3 bar and dust enrichments between 600x and 1000x. If these chondrules formed by secondary melting of mixtures of condensates that formed at different T, nebular regions with characteristics such as these would have been necessary to prevent loss of Na by evaporation and FeO by reduction from the liquid precursors, assuming that liquids and gas were hot for enough time to have equilibrated.
... The Fe-C system can have liquid in equilibrium with solid fcc c Fe alloy until temperatures above 1493° C, when d-Fe, with a bcc structure, is the stable solid phase ( Raynor and Rivlin 1988), but again, the presence of Ni stabilizes the formation of the fcc c solid crystal structure rather than the d-Fe structure at these higher temperatures (Villars et al. 1995). Similarly, the Fe-S binary system has fcc c- Fe in equilibrium with a S-bearing liquid until a temperature of 1365° C, above which the bcc d-Fe solid structure is stable ( Massalski et al. 1990), but the presence of Ni results in fcc c Fe alloy being the solid crystal structure (Hsieh et al. 1982). In these Fe-Ni ternary systems, the exact amount of Ni required to ensure the fcc c phase is the crystal structure of the solid depends on the specific system and the temperature, but the ~10 wt% Ni concentrations in our experiments in Table S1 and commonly used in other experimental studies are more than sufficient according to the referenced phase diagrams. ...
... Scott (1972) proposed that the siderophile element concentrations in 10 of the 13 iron meteorite groups are caused by crystal-liquid (magmatic) fractionation (Liu and Fleet 2001). However, from a melt containing Fe, Ni, and S in a bulk composition of the investigated meteorites, the metal phase will initially crystallize (Hsieh et al. 1982;Chabot et al. 2007). This will lead to enrichment of S in the residual melt until the eutectic point is reached and eutectic mixture of metal phase and sulfide phase would be solidified. ...
We combined high-resolution and space-resolved elemental distribution with investigations of magnetic minerals across Fe,Ni-alloy and troilite interfaces for two nonmagmatic (Morasko and Mundrabilla) IAB group iron meteorites and an octahedrite found in 1993 in Coahuila/Mexico (Coahuila II) preliminarily classified on Ir and Au content as IIAB group. The aim of this study was to elucidate the crystallization and thermal history using gradients of the siderophile elements Ni, Co, Ge, and Ga and the chalcophile elements Cr, Cu, and Se with a focus on magnetic minerals. The Morasko and Coahuila II meteorite show a several mm-thick carbon- and phosphorous-rich transition zone between Fe,Ni-alloy and troilite, which is characterized by magnetic cohenite and nonmagnetic or magnetic schreibersite. At Morasko, these phases have a characteristic trace element composition with Mo enriched in cohenite. In both Morasko and Coahuila II, Ni is enriched in schreibersite. The minerals have crystallized from immiscible melts, either by fractional crystallization and C- and P-enrichment in the melt, or by partial melting at temperatures slightly above the eutectic point. During crystallization of Mundrabilla, the field of immiscibility was not reached. Independent of meteorite group and cooling history, the magnetic mineralogy (daubreelite, cohenite and/or schreibersite, magnetite) is very similar to the troilite (and transition zone) for all three investigated iron meteorites. If these minerals can be separated from the metal, they might provide important information about the early solar system magnetic field. Magnetite is interpreted as a partial melting or a terrestrial weathering product of the Fe,Ni-alloy under oxidizing conditions.
... Additional iron meteorite compositional studies are listed in the recent review of Haack and McCoy (2003). Ni also influenced the S content of the equilibrium metallic liquid in each experiment, which is consistent with the Fe-Ni- S phase diagram (Hsieh et al. 1982). Consequently, these experiments resulted in run products with both varying Ni contents and metallic liquid S contents, which, though relevant to many iron meteorite compositions, created a major complication for isolating the effect of Ni. ...
Abstract— -Iron meteorites exhibit a large range in Ni concentrations, from only 4% to nearly 60%. Most previous experiments aimed at understanding the crystallization of iron meteorites have been conducted in systems with about 10% Ni or less. We performed solid metal/liquid metal experiments to determine the effect of Ni on partition coefficients for 20 trace elements pertinent to iron meteorites. Experiments were conducted in both the end-member Ni-S system as well as in the Fe-Ni-S system with intermediate Ni compositions applicable to high-Ni iron meteorites. The Ni content of the system affects solid metal/liquid metal partitioning behavior. For a given S concentration, partition coefficients in the Ni-S system can be over an order of magnitude larger than in the Fe-S system. However, for compositions relevant to even the most Ni-rich iron meteorites, the effect of Ni on partitioning behavior is minor, amounting to less than a factor of two for the majority of trace elements studied. Any effect of Ni also appears minor when it is compared to the large influence S has on element partitioning behavior. Thus, we conclude that in the presence of an evolving S-bearing metallic melt, crystallization models can safely neglect effects from Ni when considering the full range of iron meteorite compositions.
... In order to see if sulfide liquids are more stable than the predicted assemblages, the relative atom proportions of Fe and S were calculated for the metallic nickel–iron pyrrhotite assemblage predicted at each temperature step for dust enrichments of 500, 800, and 1000 at 10 3 bar, and are plotted on a portion of the liquid-crystal phase relations in the Fe–S binary (Chuang et al., 1986a) inFigure 15. The dashed curves in this figure are the phase boundaries that result from addition of 7% Ni to the system, taken from the work of Hsieh et al. (1982), projected onto the Fe–S plane. Under all conditions, the trajectory of the condensate compositions initially falls vertically along the left margin of the diagram until the temperature of pyrrhotite formation is reached. ...
Full equilibrium calculations of the sequence of condensation of the elements from cosmic gases made by total vaporization of dust-enriched systems were performed in order to investigate the oxidation state of the resulting condensates. The computations included 23 elements and 374 gas species, and were done over a range of Ptot from 10⁻³ to 10⁻⁶ bar and for enrichments up to 1000× in dust of Cl composition relative to a system of solar composition. Because liquids are stable condensates in dust-enriched systems, the MELTS nonideal solution model for silicate liquids (Ghiorso and Sack, 1995) was incorporated into the computer code. Condensation at 10⁻³ bar and dust enrichments of 100×, 500×, and 1000× occur at oxygen fugacities of IW-3.1, IW-1.7, and IW-1.2, respectively, and, at the temperature of cessation of direct condensation of olivine from the vapor, yields XFa of 0.019, 0.088, and 0.164, respectively. Silicate liquid is a stable condensate at dust enrichments >∼12.5× at 10⁻³ bar and >∼425× at 10⁻⁶ bar. At 500×, the liquid field is >1000 K wide and accounts for a maximum of 48% of the silicon at 10⁻³ bar, and is 240 K wide and accounts for 25% of the silicon at 10⁻⁶ bar. At the temperature of disappearance of liquid, XFa of coexisting olivine is 0.025, 0.14, and 0.31 at 100×, 500×, and 1000×, respectively, almost independent of Ptot. At 1000×, the Na2O and K2O contents of the last liquid reach 10.1 and 1.3 wt.%, respectively, at 10⁻³ bar but are both negligible at 10⁻⁶ bar. At 10⁻³ bar, iron sulfide liquids are stable condensates at dust enrichments at least as low as 500× and coexist with silicate liquid at 1000×. No sulfide liquid is found at 10⁻⁶ bar. At 10⁻³ bar, the predicted distribution of Fe between metal, silicate and sulfide at 1310 K and a dust enrichment of 560× matches that found in H-group chondrites, and at 1330 K and 675× matches that of L-group chondrites prior to metal loss.
... Chang and Hsieh (1987) computed the Fe-Ni-S phase diagram down to 700 °C using associated solution models for liquid, a statistical thermodynamic model for mss, a quasi-subregular model for metal alloy, and a pseudobinary solution model for the disulfi de, all based on their experimental work and that in the literature (cf. Chuang 1983;Hsieh 1983;Hsieh et al. 1982Hsieh et al. , 1987aSharma and Chang 1979;cf. Kress 2003). ...
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... These are three observations with potential information on the thermal history of largest Fe-Ni-S inclusions with their characteristic core-mantle texture that could be different from the smaller opaque inclusions. The crystallization sequence in the droplets can be deduced from the Fe-Ni-S phase diagram (Kullerud et al. 1969; Hsieh et al. 1982 Hsieh et al. , 1987), the Fe-S binary phase diagram (Kullerud et al. 1969), or the modified binary Fe-S diagram (Rietmeijer et al. 2008). According to these phase diagrams, the crystallization temperature and crystallization sequences are a function of the (Fe + Ni)/S ratio of the melt. ...
We report the results of high-resolution, analytical and scanning transmission electron microscopy (STEM), including intensive element mapping, of severely thermally modified dust from comet 81P/Wild 2 caught in the silica aerogel capture cells of the Stardust mission. Thermal interactions during capture caused widespread melting of cometary silicates, Fe-Ni-S phases, and the aerogel. The characteristic assemblage of thermally modified material consists of a vesicular, silica-rich glass matrix with abundant Fe-Ni-S droplets, the latter of which exhibit a distinct core-mantle structure with a metallic Fe,Ni core and a iron-sulfide rim. Within the glassy matrix, the elemental distribution is highly heterogeneous. Localized amorphous "dust-rich" patches contain Mg, Al, and Ca in higher abundances and suggest incomplete mixing of silicate progenitors with molten aerogel. In some cases, the element distribution within these patches seems to depict the outlines of ghost mineral assemblages, allowing the reconstruction of the original mineralogy. A few crystalline silicates survived with alteration limited to the grain rims. The Fe- and CI-normalized bulk composition derived from several sections show CI-chondrite relative abundances for Mg, Al, S, Ca, Cr, Mn, Fe, and Ni. The data indicate a 5 to 15% admixture of fine-grained chondritic comet dust with the silica glass matrix. These strongly thermally modified samples could have originated from a finegrained primitive material, loosely bound Wild 2 dust aggregates, which were heated and melted more efficiently than the relatively coarse-grained material of the crystalline particles found elsewhere in many of the same Stardust aerogel tracks (Zolensky et al. 2006).
The conventional smelting and refining of Ni sulfide concentrates is an effective strategy for extracting Ni from sulfide ores. However, during the smelting process, sulfur is oxidized to sulfur dioxide (SO2), which poses a significant environmental hazard. The present work investigates the feasibility of an alternative process to recover Ni as a ferronickel (FeNi) alloy while retaining the bulk of the sulfur in a solid phase (FeS), mitigating potential SO2 emissions. A Ni concentrate blended with iron was treated at 950 ?C under an Ar atmosphere for 2 h, yielding a FeNi containing ~22 wt% Ni and a residual iron sulfide containing <2.2 wt% Ni. The composition of these FeNi alloy particles is in good agreement with thermodynamic predictions.
At 900 degrees C the dry condensed system Fe-Ni-S contains two sulfides (mss and NiS2), a sulfide melt and Fe-Ni alloys gamma and alpha. The mss recedes from S-poor compositions for all mixed (Ni,Fe)(l-x)S compositions. The field of sulfide melt has been newly delineated in this study by microprobe analyses on 32 binary runs. There are two important three-phase associations in the system: mss Fe48.6Ni1.1S50.3 - gamma Fe65.0Ni35.0 - melt similar to Fe42.0Ni15.0S43.0 and vaesite Ni0.91Fe0.09S2 - mss Ni0.54Fe0.33S - S Partition coefficient D-Ni (mss/melt) was determined to be equal to (at.% Ni(mss)(0.663)/13.393. The present results are compared with those of KULLERUD et al. (1969) and FYODOROVA & SINYAKOVA (1993).
Nickel sulfide formation from nickel-containing steel residuals in the glass batch has been assumed for quite some time. Melting trials were carried out with a soda-lime-silica glass batch containing steel particles with 20% nickel. By this the above assumption was shown to be true and the exact cascade of the reaction of the metals with the sulfate of the glass melt could be pointed out. Five steps can be distinguished: sweating out the less noble elements (chromium, manganese, carbon); formation of a mixed iron nickel sulfide phase in equilibrium with the remaining iron nickel alloy; enrichment of nickel in the alloy and the sulfide phase, until complete elimination of iron; sulfidation of the remaining pure nickel and formation of a nickel-rich sulfide; oxidation to NiS. The reaction cascade found experimentally is confirmed by the authors' own thermodynamic calculations. Literature data show that nickel sulfides containing more sulfur than the 1:1 composition are not stable in the glass melt and decompose in a small "explosion". The exact composition of an NiS stone found in glass depends on its individual temperature/time history. It consists mainly of (Ni,Fe)S, which may transform to millerite. If the former sulfide melt still contains a nickel excess, the crystalline stone may also contain minor parts of other NiySx phases such as Ni9S8 or Ni7S6.
A single-particle laminar-flow furnace was used to study the oxidation of a violarite- and pyrite-containing nickel concentrate from the Forrestania mine, Australia. The composition of the reaction gas varied from N2 to N2 + 75 vol% O2 and the gas preheating temperatures ranged from 500 to 1100°C. The degree of oxidation of the material was established through chemical analysis. Optical and scanning electron microscopy were used to determine the morphology and mineralogy of the oxidation products. The concentrate studied was found to be very reactive, and it ignited at ≤500°C. Total desulphurization of this nickel concentrate was observed at 900°C with 50 vol% oxygen in the reaction gas. The microscopical examinations showed that oxidation started with the formation of a porous oxide rim, after which oxidation proceeded either via grain growth of a two-phase structure or via preferential oxidation of the outer layer - both resulting in the formation of oxide crust. Moreover, particles were found to fragment by several different mechanisms.
Dense plates of mixed Ni–Fe sulfide of a composition Ni3S2-3 mass% FeS were oxidized in a mixed O2–N2 gas stream at 923, 973 and 1023 K. The oxygen partial pressure was maintained at 2.02×104 Pa. The sample mass increased during the oxidation and the rate of mass gain was higher than in the oxidation of Ni3S2. A very small amount of SO2 gas was evolved in the initial few hundred seconds and no SO2 gas was evolved thereafter during the oxidation for 72 ks. SEM observation, EPMA and powder X-ray diffraction revealed that a multi-layered oxide film of Fe2O3, Fe3O4 and NixFe3−xO4 was formed on the sulfide surface.At the initial stage of oxidation, a thin layer of Fe oxide was rapidly formed, and the rate was controlled by the diffusion of Fe in the inner sulfide core. The activation energy was 190 kJ·mol−1. At the subsequent stage of oxidation, the layers of Fe oxide and NixFe3−xO4 grew in accordance with the parabolic rate law. The growth rate of Fe oxide was controlled by the diffusion of Fe through the oxide layer with the activation energy of 127 kJ·mol−1. The chemical diffusion coefficient of Ni in the NixFe3−xO4 layer was estimated at 10−16 to 10−17m2·s−1. The Ni concentration in NixFe3−xO4 increased with the reaction time until the composition attained NiFe2O4. Thereafter, NiO was formed between the sulfide and NiFe2O4 in the oxidation at 1023 K.
A deep analysis and mutual fitting of the data on all ternary boundary systems have resulted in obtaining information about the phase transformations in high-sulfur Fe-Ni-S compositions and in augmentation of data on the projections of the solidus surfaces in the Fe-Ni-Cu and Fe-Ni-S systems. The studies are performed using differential thermal analysis, scanning electron microscopy, and electron-probe microanalysis. The investigation carried out is a continuation of the cycle of studies dealing with an experimental construction of the phase diagrams of the ternary systems bounding the quaternary Fe-Ni-Cu-S system.
A study of the phase diagram of ternary Iron-Nickel-Sulfur (Fe-Ni-S) ternary system that is of practical importance in the extraction of Ni from its ores is presented. The isostructural phases Fe 1-xS and Ni 1-xS form a continuous solid solution from solidus temperatures at approximately 300°C. The liquid phase originating on the Ni-S side is found to extend into the ternary region, dissolving up to 42 at.% Fe. The sulfide melt along the Ni-S side has a range of 34-38.4 at.% S and dissolves up to 11.9 at.% Fe. The ternary phase diagram of the system has log f s2 values of -11.9 in the Fe-rich field and -7.27 in the Ni-rich field. The phase relationships studied at temperatures 300, 250, and 200°C shows miscibility gap arising in the central portion of the continuous monosulfide solid solution below 263∓13°C.
This document is part of Volume 11 `Ternary Alloy Systems: Phase Diagrams, Crystallographic and Thermodynamic Data', Subvolume D `Iron Systems', of Landolt-Börnstein - Group IV `Physical Chemistry'.
Tie line compositions of (Fe, Ni, Cu) (sub 1-x) S (monosulfide solid solution, mss) and Fe-Ni-Cu-S liquid, in the presence
of sulfur vapor, have been quenched from temperatures between 1,050 degrees and 1,180 degrees C. More than 80 bulk compositions
on both sulfur-rich and sulfur-poor sides of the mss field were investigated by sealed silica tube techniques.Qualitative
observations of wetting behavior suggest increasing mobility in a silicate host rock, as sulfide liquids become more Cu rich.
Partition coefficients for copper > or = 0.25, D (super mss/hq) Cu , are obtained from Ni-bearing experiments with approximately 2 wt percent Cu and no quench phases. The equation D (super
mss/hq) Cu = 0.0003 X T( degrees C) + 0.0310 X (wt % S) + 0.0069 X (wt % Cu)--1.3450 describes partitioning observed in Ni-free experiments
above 1,000 degrees C. Above 1,000 degrees C, the Ni distribution coefficient D (super mss/hq) Cu decreases with increasing temperature and/or sulfur content of the liquid.These results yield improved models describing
the fractional crystallization of natural sulfide liquids. Major element (Fe, Ni, Cu, S) compositions of ores from the Sudbury
district are shown to be entirely consistent with fractional crystallization at temperatures above 1,000 degrees C, with the
possible exception of rare samples enriched in both Ni and Cu. Sulfide liquids fractionating Ni-Fe-rich hanging-wall ores
at Sudbury, Ontario, must have been less Cu rich than previously thought. At temperatures above 950 degrees C, reduced sulfur
activity in residual liquids can result in massive late-stage bornite-rich ores.
The phase relations within the Fe9S8-Ni9S8-Cu9S8 section of the system Fe-Ni-Cu-S at 760similar toC were investigated in silica glass tubes. A complete "quaternary" solid-solution (Hz-Iss) between heazlewoodite solid-solution (Ni,Fe)(3+/-x)S-2 and intermediate Cu1+/-xFe1+/-yS2 solid-solution was established. The possibility of direct crystallization of pentlandite (Pn) from Cu-containing sulfide melt is uniikely, as no primary Pn was found to be stable in the high-temperature associations. Experiments performed at the same conditions with Pt, Pd or Rh added in small quantities reveal the contrasting behavior of platinum-group elements (PGE). Pt preferentially forms its own minerals, either Pt-Fe alloys in association with Fe-rich base-metal sulfides (BMS) or platinum sulfides in Ni- and Cu-rich assemblages. At 760degreesC, sulfur fugacity [f(S-2)] varies from -10.5 [log f(S-2)] where gamma(Fe,Ni,Pt) alloy is stable to log f(S-2) greater than or equal to -1.1 where Cu(Pt,Ni)(2)S-4 is present. Palladium enters sulfide solid-solutions, with up to 1.5 at.% in Hz-Iss and 0.9-1.1 at.% in Ni-rich monosulfide solid-solution (Mss), The behavior of Rh is remarkable; it may concentrate in BMS, especially Mss, accounting for up to 2.6 at.% Rh, or form Rh alloys or sulfides, under very low or very high f(S-2), respectively. The application of the present experiments to PGE-bearing sulfide deposits indicates that sulfide solid-solutions were in most cases the temporary collectors of the light PGE before the appearance of Pn. During subsolidus recrystallization of the high-temperature BMS, Pd and Rh partition into Pn or form their own secondary minerals. PGE deposits with a predominance of Pt-Fe alloys, such as those occurring in mantle rocks exposed in ophiolites (Corsica. New Caledonia) or kimberlites, and in layered complexes (e.g., the Merensky Reef, Bushveld Complex) are consistent with derivation from a S-poor sulfide melt, yielding early-formed Pt-Fe alloys. A similar origin may be inferred for the alloy type of Pt mineralization, which occurs in some crustal sequences of ophiolites and in Alaskan-type complexes, despite the very low amount of BMS present. Even in these low-S deposits, high f(S-2) may be reached locally as a result of the appearance of a Cu-rich sulfide liquid, derived by fractionation or by immiscibility from an original Fe-rich sulfide melt.
We have been exploring ways to quantitatively assess the extent to which fractionation of sulfide melt has effected variations in composition within magmatic sulfide ore bodies. Our approach has been to determine by experiment the crystallization paths of sulfide liquids in temperature and composition dimensions. In this paper, the results of new major-element partitioning experiments below 1050 °C in the nickel-free system are presented and summarized along with new and previous work in the Fe–Ni–Cu–S quaternary. The partition coefficients D for Cu between monosulfid solid solution (mss) and sulfide liquid in the Ni-free system (DCu = (wt.% Cu in mss)/(wt.% Cu in liquid)) cluster near 0.3, but decrease to nearly 0.1 for Cu-rich, S-poor liquids near 1000 °C. DNi also declines with decreasing sulfur content of the liquid, but increases with decreasing temperature. Preliminary data indicate that DNi exceeds 1.0 in low-Ni liquids with greater than 16 wt.% Cu, at 1050 °C. The quality of available data on the Fe–Ni–Cu–S system currently exceeds the sensitivity of crystallization models based on the distribution coefficient approximation for major elements. However, we present equations for variable distribution coefficients for Ni and Cu that can be incorporated into calculations of the ratio of trapped initial liquid to fractionated solid for bulk ore samples, using D values for platinum group elements from the literature. Fractionation can then be modeled quite well using an iterative approach, with D values changing in response to liquid composition with each increment of crystallization along an assumed temperature path.
The Ilafegh 009 meteorite is an impact melt rock from an EL‐chondritic parent body. Its mineralogic assemblage is the result of rapid crystallization after shock‐induced melting. We report here an analytical transmission electron microscopy (ATEM) study of the major minerals of this meteorite (enstatite, plagioclase, Fe‐Ni metal and sulfides). Based on this study, we discuss the crystallization sequence and the further evolution of the rock in the solid state.
Microstructure and microanalyses confirm that the mineralogy of Ilafegh 009 results from the crystallization of an EL‐chondritic melt. The high compositional variability of plagioclases and the presence of silica‐rich glass pockets indicate fast cooling. During crystallization, the large enstatite grains trapped a large number of phases (plagioclase, silica‐rich glass and enstatite nuclei). Sulfides (troilite, alabandite and daubreelite) form finely polycrystalline areas and reveal a complex crystallization sequence. Although Fe‐Ni metal grains formed during rapid cooling, their microstructures show that some postsolidification process occurred in Ilafegh 009. A large number of tiny Ni‐P‐Si‐rich precipitates were detected that formed as a result of exsolution of elements that become insoluble in kamacite at low temperature.
Finally, the microstructure (dislocation arrangements and phase transformations) observed in enstatite and Fe‐Ni metal attests that Ilafegh 009 also experienced a moderate postsolidification shock event.
The low-temperature, Fe-rich portion of the Fe-Ni-S phase diagram was determined from Fe-Ni-S alloys (2.5,5,10,20, and 30 wt.% Ni, 10 wt % S, balance Fe) heat treated at 100 °C intervals from 900 to 300 °C. The microstructure and microchemistry of the phases in the heat treated Fe-Ni-S alloys were studied using a high-resolution field-emission gun (FEG) scanning electron microscope (SEM), electron probe microanalyzer (EPMA), and analytical electron microscope (AEM). Tieline compositions were obtained by determining the average phase composition and by measuring compositional profiles across interphase interfaces with the EPMA and AEM. At 600 °C and below, at least one phase was <1 Μm in size requiring the use of the AEM for analysis. The measured α + FeS, γ+ FeS, and α + γ
+
FeS boundaries in the Fe-rich corner of the Fe-Ni-S isotherms are consistent with previous studies. However, two new phases were observed for the first time coexisting with γ and FeS phases: FeNiγ′′ (∼52 wt.% Ni) at 600 and 500 °C and Ni
3Fe, ordered Ll
2,γ′ (∼64 wt.% Ni) at 400 °C. New ternary isotherms are given at 600,500, and 400 °C that include the newly determined γ+γ′′ + FeS and the γ + γ′ + FeS three-phase fields. The effects of S on the phase boundaries of the α + γ phase field and the application of the Fe-Ni-S phase diagram to explain the microstructure and microchemistry of the metallic phases of stony meteorites are also discussed.
Accurate relationships between equilibrium partition coefficients and solute concentration are required for the prediction
of solute redistribution during solidification. Thermodynamic analyses are presented to relate these coefficients to fundamental
thermodynamic quantities. Using the most accurate data available, partition coefficients are calculated for ten Fe−X (X=Al,
C, Cr, Mn, Ni, N, P, Si, S, Ti) binary systems and compared with literature values. Equations are presented to allow for prediction
of these partition coefficients as a function of temperature, as well as liquidus temperature as a function of composition.
In addition, partition coefficient values are examined for the ternary systems Fe−Cr−C, Fe−Mn−Ni, and Fe−Ni−S.
A thermogravimetric method employing H2-H2S-Ar gas mixtures was used to measure the thermodynamic properties and phase equilibria of the Fe-Ni-S system. The equilibrium sulfur pressures in the ternary monosulfide phase and an adjacent two-phase region were measured between 700 to 900C. Isothermal sections at 700, 750, 800, and 850C are constructed as well as stability diagrams for the same temperatures.
The liquidus and solidus surfaces of the ternary Fe-Ni-Cu system are plotted using differential thermal analysis. The structure
and composition of the samples were controlled by scanning electron microscopy and electron-probe microanalysis. The results
obtained reflect the positions of the liquidus isotherms in the Fe-Ni-S system and agree well with the reported data, which
indicates the correctness of the chosen experimental technique. The results reflecting the position of the solidus surface
in the Fe-Ni-S system over a wide composition range are presented for the first time.
The high-temperature-corrosion behavior of alloy 800H has been studied in an oxidizing (SO2–O2,
PO2 P_{O_2 }
=0.23 atm,
Ps2 P_{s_2 }
=1.910–29 atm) and a reducing (H2–H2S–CO–CO2–N2,
PO2 P_{O_2 }
=1.510–18 atm
Ps2 P_{s_2 }
=4.310–8 atm, ac=0.03) sulfidizing environment, at 750C and 850C, respectively. When corroded in SO2–O2, the protective chromia scale which developed on the alloy in the early stages cracked and spalled in quite a short time period. This led to the growth of iron and nickel sulfides beneath the chromia layer, causing more chromia spallation. When correded in H2–H2S–CO–CO2–N2, the alloy exhibited breakaway corrosion in about 35hr, at which stage liquid nodules formed on the sample surface. The nodules were studied in detail and were found to consist of three layers. The growth mechanism of such nodules is proposed.
Partition coefficients (D) for metal/sulfide liquid, troilite/sulfide liquid, and schreibersite/ sulfide liquid have been experimentally determined for Ag, Au, Mo, Ni, Pb, Pd, and Tl. With these partition coefficients, it should be possible to better understand the 107Pd-107Ag and 205Tl-205Pb systems of iron meteorites. In general, our schreibersite/metal and troilite/metal partition coefficients for “compatible” elements are quite similar to those inferred from natural assemblages. In contrast, these same partition coefficients for “incompatible” elements often do not even qualitatively agree with analyses of iron meteorites. We suggest that analyses of incompatible elements in iron meteorites may sometimes be dominated by minor/trace phases. Identification of such phases may allow refinement of the initial isotopic composition of Pb in the early solar system. If our trace impurity model is correct, it may also be possible to reconcile iron meteorite cooling rates inferred from silver isotopic systematics with those deduced from metallography.
Mineral phases from opaque assemblages (OAs) in Ca, Al-rich refractory inclusions (CAIs), chondrules and matrix in C3V meteoites were chemically analyzed and compared with experimentally determined phase equilibria and partitioning data in the NiFeS, NiFeS and NiFeO systems to estimate the temperature, sulfur fugacity (fS2) and oxygen (fO2) of OA formation. The kinetics of dissolution and exsolution of metallic phases in the NiFeRu system were used to constrain the thermal history of OAss that occur in CAIs. Based on this work, we suggest that OAs formed after the crystallization of host CAIs by exsolution, sulfidation and oxidation of precursor alloys at low temperatures (≈ 770 K) and higher than solar gas fS2 and fS2. Our model contrasts with previous models that call upon the formation of CAI OAs by aggregation of previously formed phases in the solar nebula prior to the crystallization of CAIs. Opaque assemblages in CAIs and chondrules probably originated as homogeneous alloys during melting of the silicate protions of CAIs and chondrules. The compositions of these precursor alloys reflect high-temperature and low-fO2 conditions in the early solar nebula. The similarities in the temperature, fS2 and fO2 of equilibrium for OAs that occur in CAIs, chondrules and matrix suggest that these three components of C3V meteorites share a common, late low-temperature history. The mineral phases in OAs do not preserve an independent history prior to CAI and chondrule melting and crystallization, but instead provide important information on the post-accretionary history of C3V meteorites and allow us to quantify the temperature, fS2 and fO2 of cooling planetary environments.
The characteristics of the sulfide and metal phases of Derrick Peak, Cape York, Grant, Gibeon, and Santa Clara iron meteorite samples are examined. The textures and mineralogies of the samples are described. The effects of thermal and shock events on the distribution of Ag, and the relationship between Ag-107 and Pd are investigated. The correlation between the thermal histories and metal and sulfide nodules of the Gibeon and Santa Clara specimens is analyzed. It is noted that the Pd-107-Ag107 systematics involve the isotopic chemistry and cooling history of iron meteorites, the intensity of late extraterrestrial shock occurrences, and thermal processing.
The thermodynamic activity of sulfur in the β1-Ni3S2, β2-Ni4S3, γ-Ni6S5 and δ-NiS phases was determined as a function of composition over the temperature interval, 823 to 1023 K, using a gas equilibration technique. The data obtained in the present study as well as those reported in the literature are evaluated to yield thermodynamic equations of state for all the intermediate phases. Several forms of the Ni-S phase diagram are presented. The previously reported “Ni3S2” phase was found to consist of two phases designated as β1-Ni3S2 and β2-Ni4S3 in the present study.
The liquidus compositions and the tie-lines for the solid alloy plus liquid sulfide two-phase region were determined for the iron-nickel-sulfur system in the temperature range 1473 to 1673 K. Experiments were conducted by sampling the liquid sulfide in equilibrium with the alloy phase and chemically analyzing the sulfide. The alloy was quenched and analyzed by electron microprobe. The results represent a significant revision to existing data. © 1978 American Society for Metals and The Metallurgical Society of AIME.
The S-rich portion of the Fe-Ni-S system has been investigated between 100 degrees and 1000 degrees C. under equilibrium vapor
pressures with especial emphasis on the FeS 2 -NiS 2 join. Pyrite (FeS 2 ) and vaesite (NiS 2 ) coexist between 729 degrees + or - 3 degrees and 137 degrees + or - 6 degrees C. Above this temperature range, a (Fe, Ni)
(sub 1-x) S solid solution coexists with S liquid, whereas below 137 degrees C. bravoite [(Fe, Ni)S 2 ] is stable on the join between pyrite and vaesite. The solubility of FeS 2 in vaesite is a maximum of 27.9 wt % at 729 degrees C.; other points on the solvus are 13.5% at 600 degrees C, 6.5% at 500
degrees C, 2.5% at 400 degrees , 0.7% at 300 degrees , and 0.1% at 200 degrees C. The heat of mixing, delta H, is constant
at 9.8 kcal/mole. The maximum NiS 2 solubility in pyrite of 7.7 wt % also occurs at 729 degrees C. It decreases to about 6.8% at 700 degrees C. but could not
be determined at lower temperatures. When pyrite and vaesite coexist, the vaesite solvus is a useful geothermometer. A determination
on material from the Kasompi Mine, Katanga, indicates a formation temperature of 390 degrees C. Bravoite, generally a secondary
mineral, can form only below 137 degrees C. C. Most nickeliferous pyrites were deposited at relatively low temperatures where
the equilibrium Ni solubility is well below 1%. It is concluded, in the light of the experimental evidence, that most of the
Ni occurs in metastable solid solution in these pyrites.
Phase diagram and thermodynamic data for twenty ternary copper-silver-X alloy systems - where X represents Al, Au, Cd, Fe, Ge, In, Mg, Mn, Ni, P, Pb, Pd, Re, S, Sb, Se, Sn, Te, Ti or Zn - were compiled and critically evaluated. Of the twenty ternary systems, thermodynamic data are available for only the seven systems containing Au, Pb, Pd, S, Sn, Te and Zn. the high-temperature phase relationships in the iron-rich region of the Cu-Fe binary system were also evaluated and a recommended phase diagram is presented. Refs.
The activity of sulphur inside and at the boundaries of the homogeneity range of “Ni3±x S2” was accurately determined by stepwise reduction with hydrogen at temperatures between 815 and 1044 K. It is suggested that a second order phase transition inside the homogeneity range takes place.
There are many phases containing copper and sulfur that are of great importance in the metallurgy of copper. Information on numerous binary systems of elements with copper and with sulfur are available in a number of places, including Volume I of this series, However, papers reporting information on phase relationships and phase diagrams on ternary and higher-order systems are scattered far and wide in the scientific and technical literature. These data are to be found in many forms, and often the information contained in a publication is not related to that in other papers on related systems. Professor Chang, Dr. Neuman, and Dr. Choudary have devoted a great deal of effort information on 25 Cu-S-X systems (where X is another metal). The task has been a large one because it has been necessary to collate data on the various phases, to prepare carefully diagrams representing phase equilibria and to relate thermodynamic data with the equilibria among phases. The reader will find this volume a particularly useful one when used in conjunction with Monographs I and II of this series: Selected Thermodynamic Values and Phase Diagrams for Copper and some of Its Binary Alloys, and Thermodynamic Properties of Copper and Its Inorganic Compounds, respectively.
An associated solution model is applied to describe the thermodynamic behavior of Fe-S liquid. This model assumes the existence
of ‘FeS’ species in addition to Fe and S in the liquid. With two solution parameters for each of the binaries Fe-‘FeS’ and
‘FeS’-S, this model accounts for the compositional dependence of the thermodynamic properties of Fe-S liquid from pure Fe
to pure S over a wide range of temperature. The binary Fe-S does not contribute significantly to the excess Gibbs energy of
the liquid due to the rather small dissociation constant of ‘FeS’ to Fe and S. Using this model for the liquid phase and a
defect thermodynamic model for the pyrrhotite phase, the Fe-S phase diagram is calculated. The calculated diagram is in excellent
agreement with the experimental data, accounting for the range of homogeneity of pyrrhotite at all temperatures. Both the
thermodynamic and phase diagram data are obtained from the literature.
An associated solution model is applied to describe the thermodyanmic properties of the liquid Ni-S phase. This model assumes
the existence of ‘NiS’ (l) species in the liquid in addition to Ni(l) and S(l). With two solution parameters for the binaries
Ni-‘NiS’ and ‘NiS’-S, this model is able to describe the thermodynamic behavior of the liquid phase over a wide range of temperature
and composition. Using this model for the liquid phase, a statistical thermodynamic model for the monosulfide phase and empirical
thermodynamic equations for β1-Ni3S2 and β2-Ni4S3, the Ni-S phase diagram is calculated. The calculated diagram is in excellent agreement with the available experimental data
with the exception that the eutectic composition for the equilibrium L1 + δ + η and those of the two liquids for the equilibriumL
1
+ L
2
+ η differ from the experimental data by more than 2 at. pct S.