Molten Sulfur Research Articles

Density of molten sulfur in the 334–508 K range

As the density of elemental sulfur was determined on slowly cooling from 508 K, it was unexpected for the metastable molten state to be maintained to temperatures as low as 334 K, thus expanding by about 20 K the T-range within which experimental data become available. In the 334–430 K range, the density ρ of the metastable molecular melt was fitted to ρ (g cm −3) = 2.18835–0.00098187 T (K), subsequently leading to volumic expansion coefficients α V( T) = −(1/ ρ( T))( ∂ρ/ ∂T) P of 5.28 × 10 −4 K −1 at 334 K and 5.56 × 10 −4 K −1 at 430 K.

Cold Fission

Global Technologies is working on a nuclear voltaic cell consisting basically of a semiconductor and an amount of radioactive material. By replacing solid semiconductors with molten selenium and molten sulfur, GT's nuclear battery could run on much more powerful radiation than a beta cell and therefore generate more electricity

Pressure oxidation leaching of chalcopyrite: Part II: Comparison of medium temperature kinetics and products and effect of chloride ion

Pressure oxidation reaction kinetics and products are compared for the recovery of copper from a chalcopyrite concentrate under medium temperature conditions at 125–150 °C, as patented and promoted by various commercial operations, normally referred to as the Anglo/UBC, CESL and NSC (nitrogen species catalysed) processes. The main aim was to compare the effect of additives on the dispersion of molten sulfur and recovery of copper, and develop a better understanding of the role of chloride ion. Greater than 94% copper was extracted from the concentrate under all process conditions (except NSC) within 30 min. The extraction of the remaining copper in some instances took substantially longer due to poor dispersion of sulfur and agglomeration of the sulfide minerals. The partial oxidation of sulfide to elemental sulfur was about 70–80% at 150 °C and was greater in the presence of chloride ion and at higher initial acidity. Iron was leached and re-precipitated forming a number of different phases depending upon the acidity and salinity. These phases including hematite, jarosite and goethite were characterised using Quantitative X-ray Diffraction (QXRD) analysis. Hematite formation was favoured at higher temperatures (≥ 150 °C), low acidity and low to moderate salinity. Goethite formation was favoured at lower temperatures (< 150 °C) and by low acidity and low salinity. Jarosite was formed under conditions of moderate to high acidity and its formation was enhanced/stabilised in the presence of sodium ions. It was demonstrated that the basic copper salt, antlerite, could be produced under conditions of low acidity. Chloride ion addition and high acid concentrations enhanced copper extraction kinetics and recovery, and inhibited the oxidation of sulfur to sulfate. This suggests that chloride ion is adsorbed on the sulfur surface to restrict direct oxygen reaction. Chloride ion also enhances the anodic oxidation of mineral sulfides and the dispersion of molten sulfur.

Discharge properties of sodium-sulfur batteries at room temperature

The sodium/sulfur(Na/S) battery has many advantages such as high theoretical specific energy(760Wh/kg), and low material cost based on the abundance of electrode material in the earth. It has been reported that the electrochemical properties of sodium/sulfur cell above , utilized a solid ceramic electrolyte and liquid sodium and sulfur electrodes. A lot of researches have been performed in this field. Recently, Na/S battery system was applied for electricity storage system for load-leveling. One of severe problems of sodium/sulfur battery was high operating temperature above , which could induce the explosion and corrosion by molten sodium, sulfur and polysulfides. In order to develop sodium battery operated at low temperature, sodium ion battery has been studied using carbon anode, and sodium oxides cathodes. However, the energy densities of the sodium ion batteries were much lower than high temperature sodium/sulfur cell. In this study, the sodium/sulfur battery with 1M is tested at room temperature. The charge-discharge mechanism was discussed based on XRD, DSC, SEM and EDS results.

Long-term eruptive activity at a submarine arc volcano

Three-quarters of the Earth's volcanic activity is submarine, located mostly along the mid-ocean ridges, with the remainder along intraoceanic arcs and hotspots at depths varying from greater than 4,000 m to near the sea surface. Most observations and sampling of submarine eruptions have been indirect, made from surface vessels or made after the fact. We describe here direct observations and sampling of an eruption at a submarine arc volcano named NW Rota-1, located 60 km northwest of the island of Rota (Commonwealth of the Northern Mariana Islands). We observed a pulsating plume permeated with droplets of molten sulphur disgorging volcanic ash and lapilli from a 15-m diameter pit in March 2004 and again in October 2005 near the summit of the volcano at a water depth of 555 m (depth in 2004). A turbid layer found on the flanks of the volcano (in 2004) at depths from 700 m to more than 1,400 m was probably formed by mass-wasting events related to the eruption. Long-term eruptive activity has produced an unusual chemical environment and a very unstable benthic habitat exploited by only a few mobile decapod species. Such conditions are perhaps distinctive of active arc and hotspot volcanoes.

Interfacial studies of liquid sulphur during aqueous pressure oxidation of nickel sulphide

Oxidative pressure leaching involves treating a finely ground concentrate, using autoclaves, in an acidic sulphate media under an oxygen atmosphere at around 150 °C. Leaching kinetics are more favourable above the melting point of sulphur (119 °C), however, it has been found that molten elemental sulphur has a tendency to occlude unreacted minerals and inhibit the diffusion of dissolved oxygen to the mineral surface, halting the reaction. Surfactants, such as ligninsulphonates, have found use in dispersing molten sulphur and allowing for higher metal recoveries in similar technologies such as the oxidative pressure leaching of zinc sulphide concentrates. In this study interfacial tensions between molten sulphur and the aqueous solution are measured along with the contact angle made by molten sulphur on pentlandite, (Ni, Fe) 9S 8 surfaces. To this end, we calculate the molten sulphur–mineral work of adhesion and determine the effects of solution chemistry and surfactant addition. It has been found that the presence of ligninsulphonates significantly reduces the work of adhesion between molten sulphur and pentlandite suggesting that surfactants will be equally effective in case the process is commercialized.

State of sulfur behind shock fronts

The state parameters of sulfur behind a shock front are calculated taking into account the possibility of destruction of the basic state S8 to S2 at temperatures above 103 K. The Hugoniot of S2 at temperatures above 103 K and pressures above 10 GPa was constructed using Hugoniot of liquid carbon disulfide and assuming that carbon disulfide decomposes into sulfur and carbon. Calculated Hugoniots of crystalline and molten sulfur are compared with experimental data.

Bathymetric and geochemical investigation of Kawah Ijen Crater Lake, East Java, Indonesia

A bathymetric survey of Kawah Ijen crater lake was conducted by acoustic sounding in 1996 to compare the lake morphology with those measured in 1922, 1925 and 1938, and to calculate the present lake volume. Even though the lake experienced several hydrothermal eruptions, the maximum depth became shallower (182 m) than before (200 m), resulting in a reduced lake volume (3.0×10 7 m 3). Fifty-two major and minor constituents including rare earth elements and polythionates (PT) of the lake waters at various depths were determined by ICP-AES, ICP-MS and HPLC, respectively. These ions except for several volatile elements are taken up by lake fringe through congruent dissolution of pyroclastics of Kawah Ijen volcano. Most ions are homogeneously distributed throughout the lake, although PT showed a considerable vertical variation. Rare earth elements (REE) in the Kawah Ijen water as well as those from other hyper-acidic crater lakes show distribution patterns likely due to the three rock dissolution (preferential, congruent and residual) types, and their logarithmic concentrations linearly depend upon the pH values of the lake waters. Using the PT degradation kinetics data, production rates of PT, injection rates of SO 2 and H 2S into the lake were estimated to be 114, 86 and 30 tons/day, respectively. Also travel time of the spring water at the Banyupahit Riverhead from Kawah Ijen was estimated to be 600–1000 days through the consideration of decreasing rates of PT. Molten sulfur stocks containing Sn, Cu, Bi sulfides and Pb-barite exposed on the inner crater slope were presumed to be extinct molten sulfur pools at the former lake bottom. This was strongly supported by the barite precipitation temperature estimated through the consideration of the temperature dependence of Pb-chlorocomplex formation.

Body and Cosmos: Pasolini, Mishima, Foucault

1. The Dismembered Body "The human body was entering a machinery of power that explores it, breaks it down, and rearranges it."— Michel Foucault, Discipline and Punish On March 2, 1757, Robert-François Damiens, who attempted to kill King Louis XV with a penknife, was condemned as a regicide "to make the amende honorable before the main door of the Church of Paris," where he was to be "taken and conveyed in a cart, wearing nothing but a shirt, holding a torch of burning wax." Then, "the flesh will be torn from his breasts, arms, thighs, and calves with red-hot pincers . . . and, on those places where the flesh will be torn away, poured molten lead, boiling oil, burning resin, wax and sulphur melted together and then his body drawn and quartered by four horses" (qtd. in Foucault 1975a, 3).1 But the horses did not succeed in pulling Damiens apart: Finally, the executioner, Samson, said to Monsieur Le Breton that there was no way or hope of succeeding, and told him to ask their Lordships if they wished him to have the prisoner cut into pieces. . . . After two or three attempts, the executioner Samson and he who had used the pincers each drew out a knife from his pocket and cut the thighs where the trunk of the body ends instead of severing the legs at the joints; the four horses . . . carried off the two thighs after them, namely, that of the right side first, the other following; [End Page 201] then the same was done to the arms, the shoulders, the arm-pits and the four limbs; the flesh had to be cut almost to the bone. . . . One of the executioners . . . said shortly afterwards that when they had lifted the trunk to throw it on the stake, he was still alive.2 (4-5) Readers will have recognized in these passages the surgically precise description of Damiens's torture that forms the opening of Discipline and Punish (1975a), the best-known book by Michel Foucault, in which he aims to describe and denounce "the disciplinary society." But here is the description of another victim of torture: After hunting for an hour, they found a stray cat small enough to ride in the palm of Noboru's hand, a mottled, mewing kitten with lackluster eyes. . . . Scattered through the gloom in the shed, the five naked boys stood rooted, their eyes glittering. (Mishima 1963,56, 58) Noboru slams the cat several times against a beam. The kitten had bounced off the log for the final time. Its hind legs twitched, traced large lax circles in the dirt floor, and then subsided. The boys were overjoyed at the spattered blood on the log. . . . Dull red blood oozed from the kitten's nose and mouth, the twisted tongue was clamped against the palate. "C'mon up close where you can see. I'll take it from here." Unnoticed, the chief had put on a pair of rubber gloves that reached up to his elbows; now he bent over the corpse with a pair of gleaming scissors. Shining coolly through the gloom of the shed, the scissors were magnificent in their cold, intellectual dignity: Noboru couldn't imagine a more appropriate weapon for the chief. Seizing the kitten by the neck, the chief pierced the skin at the chest with the point of the blade and [End Page 202] scissored a long smooth cut to the throat. Then he pushed the skin to the sides with both hands: the glossy layer of fat beneath was like a peeled spring onion. The skinned neck, draped gracefully on the floor, seemed to be wearing a cat mask. The cat was only an exterior, life had posed as a cat. . . . "What do you think? Doesn't it look too naked? I'm not sure that's such a good thing: like it was...

Effect of Ultrasonic Wave Irradiation on the Electrical Conductivity of the Undoped and Doped Molten Sulfur with Some Inorganic Materials

The electrical conductivity and the activation energy of conduction were measured up to 340°C for undoped sulfur melts and doped sulfur melts with 5 mol% LiF, 5 mol% NaF, 13.4 mol% NaCl, 1 and 5 mol% KCl, 5 mol% NaBr, 5 mol% Se, 5 mol% NaBr + 5 mol% Se, 5 mol% Na2SO4, 5 and 10 mol% Na. The effect of irradiation of ultrasonic waves of 20 kHz was studied. The electrical conductivity generally increased with increasing temperature above 200°C with a variety of temperature dependencies. The addition of NaBr, Se, LiF, Na2SO4, NaBr + Se, and KCl caused an increase in conductivity in this order by max. two orders of magnitude. For sulfur melts doped with 5 and 10 mol% Na, a wide jump of electrical conductivity occurred at 245°C, giving exceedingly high electrical conductivities above this temperature. By the irradiation of ultrasonic waves, the electrical conductivity was raised together with the formation of jump for Se, NaBr + Se, 5 mol% Na, LiF, Na2SO4, NaBr, and NaF. The largest irradiation effect was observed for 10 mol% Na, for which the jump temperature was 190°C. The activation energies classified into low, medium, and high groups were obtained. The assumption of microscopic temperature was proposed, which was found to explain the electrical conductivity of irradiated melts.

Pennsylvania German sulfur-inlaid furniture: characterization, reproduction, andageing phenomena of the inlays

Eighteenth-century Pennsylvania German furniture inlaid with an ivory-colouredmaterial was first mentioned in the art historical literature in 1958. Since thattime, there has been substantial confusion about the composition of these inlays,the source of their colour and their method of manufacture. In 1977, a number ofthese inlays were identified as an unspecified allotrope of sulfur. Eighteen yearslater, a second type of ivory-coloured eighteenth century furniture inlay that didnot contain sulfur was identified, and a method of reproducing the sulfur inlays bypouring molten sulfur into an incised decoration was demonstrated. Thereproductions were structurally successful, containing the air bubble inclusionsthat are observed in the eighteenth-century inlays, but they were thebright yellow colour that is characteristic of α-S8,the allotrope of sulfur typically observed at ambient temperatures. Fiveeighteenth-century Pennsylvania German ivory furniture inlays werecharacterized by x-ray diffraction (XRD), Fourier transform infraredspectroscopy, scanning electron microscopy energy-dispersive x-raymicroanalysis, energy dispersive x-ray fluorescence, colorimetry and gaschromatography–mass spectrometry to identify their compositions. Four of theeighteenth-century inlays were found to be pure α-S8.The inlays were further characterized by colorimetry and non-spinningDebye Scherrer XRD to identify the source of the ivory colourobserved in the eighteenth century α-S8.Data from these experiments suggest that the ivory colour is caused by a particlesize decrease of the sulfur that may result from repeated climatic cycling. Thiswould occur over the course of 200 years spent in an uncontrolled environment,and artificial ageing experiments will be used to determine if it is due to the lowthermal conductivity of sulfur, a property responsible for the macroscopiccracking and spalling of sulfur in natural history collections. The composition of asulfur inlay repair and an eighteenth-century non-sulfur ivory-coloured inlay arealso presented, along with their roles in the common misconceptions about sulfurinlay.

Pressure sulpuric acid leaching of a sulphide concentrate to recover copper, nickel and cobalt

Ore from the Jaduguda mines, India, includes significant contents of important metals,1 such as Cu (0.1%), Ni (0.1%), Co (0.006%) and Mo (0.02%), together with appreciable amounts of other valuable materials, such as apatite (3–4%), rare earths (0.1% including Y) and magnetite (5.5%). The purpose of the by-product recovery plant of the uranium mill is to recover as much of these minerals as possible to augment India’s supply. It currently produces a complex sulphide concentrate at the rate of about 1200 t/year, which yields a high-grade copper concentrate and a low-grade silicate tailing containing Cu and Ni, together with a salable molybdenum concentrate. The copper concentrate was formerly sold to the Indian Copper Complex (ICC) at Ghatsila, but of late the ICC has discontinued processing of the concentrate because of its high nickel content. As a result, the copper concentrate has remained stockpiled for want of a suitable process. This product, which was previously designated a copper concentrate, but is now referred to as a sulphide concentrate, comprises 15% copper, 10.85% nickel and 0.37% cobalt (Table 1). Several processing options present themselves and some have been tried at various institutes in India. Mukherjee et al.2 peformed tests at kilogram scale in which roasting in the presence of NaCl in the temperature range 400–500°C was followed by water leaching and solution purification. The three metals, copper, nickel and cobalt, were separated from the leach liquor of salt-roasted material as their sulphate salts by solvent extraction3 with D2EHPA for subsequent recovery in the desired form. The salt roast–leach–solvent extraction– electrowin route was also followed at NML4 for recovery of the metals as electrolytic-grade cathodes. Because of excessive corrosion during roasting, however, the process was considered unfavourable. Other important process routes for the extraction of metals from sulphide concentrates are ferric chloride leaching5 and cupric chloride–O2 leaching6 in acid conditions. Although high recoveries of the metals are often achieved, ferric chloride leaching is also known to present corrosion problems and, therefore, has not been considered by Indian investigators for this concentrate. Preliminary experiments with pressure leaching in acidic conditions are reported to have yielded metal recoveries of 70–75% Ni and 10–20% Cu.7,8 Despite these developments, it has long been considered that smelting is likely to remain the principal processing route for sulphide concentrates. This view is being challenged through pressure-leaching developments by Dynatec and Cominco Engineering Services, Ltd. (CESL), in Canada, the installation at Mt. Gordon in Queensland, Australia, and the very recent announcement by Phelps Dodge.9 The CESL process10 for copper concentrate, which uses an oxidative pressure leach with a mixed sulphate–chloride solution, is reported to have been piloted successfully. Chloride ions play a catalytic role and are required to prevent excessive sulphur oxidation that would otherwise make the process uneconomic. Pressure leaching is followed by solvent extraction and electrowinning. The Dynatec process11 for chalcopyrite concentrate treatment also uses chloride additions to the leach liquor to minimize sulphide oxidation to sulphur. In addition, fine coal is used as a dispersant for the molten sulphur formed under the leaching conditions in the autoclave. This is much cheaper than the sodium or calcium lignosulphonate or quebracho used as additives in the zinc concentrate pressureleach process. Solvent extraction is the process of choice for copper recovery from the leach liquor. The Activox process11 is claimed to offer the potential to treat sulphide concentrate directly without the need for intermediate pyrometallurgical treatment. The process involves fine grinding and low-pressure oxidative leaching. The autoclave leaching conditions are typically 100°C at an oxygen pressure of 100 kPa with a residence time of 4 h for chalcopyrite oxidation. The solution generated by leaching is finally treated by solvent extraction and electrowinning. Recently,12 a two-stage acid pressure leach at 140°C and pO2 of 600 kPa was applied to a low-grade copper–nickel concentrate containing 2% Ni, 0.43% Cu and 6.2% Mg, when it was recognized that a preleach step was required to recover more than 90% of metals.12 Acid pressure leaching was deemed to merit consideration as a potential means of extracting the valuable metals from the Jaduguda sulphide concentrate.

Molten sulphur-dominated fluids in the origin of a native sulphur mineralization in lacustrine evaporites from Cervera del Rio Alhama (Cameros Basin, NE Spain)

During the regional and petrologic study of the Cameros Basin, vein deposits containing native sulphur, gypsum, quartz and rare sphalerite were found enclosed in lacustrine evaporites. The fluid inclusion study of the coeval quartz crystals revealed that the aqueous fluids were extremely scarce during vein formation. Surprisingly, the textural study, microthermometry and qualitative Raman analyses of these inclusions proved that the main fluid-trapped during vein formation was a mixture of molten sulphur and volatiles (N2, CO2 and H2S). As far as we know, this is the first time that an almost pure sulphur-bearing fluid is described to occur in sulphur deposits.

Sulfur geochemistry of hydrothermal waters in Yellowstone National Park, Wyoming, USA. II. Formation and decomposition of thiosulfate and polythionate in Cinder Pool

Cinder Pool is an acid-sulfate-chloride boiling spring in Norris Geyser Basin, Yellowstone National Park. The pool is unique in that its surface is partially covered with mm-size, black, hollow sulfur spherules, while a layer of molten sulfur resides at the bottom of the pool (18m depth). The sulfur speciation in the pool was determined on four different days over a period of two years. Samples were taken to evaluate changes with depth and to evaluate the importance of the sulfur spherules on sulfur redox chemistry. All analyses were conducted on site using a combination of ion chromatography and colorimetric techniques.Dissolved sulfide (H2S), thiosulfate (S2O32−), polythionates (SxO62−), and sulfate were detected. The polythionate concentration was highly variable in time and space. The highest concentrations were found in surficial samples taken from among the sulfur spherules. With depth, the polythionate concentrations dropped off. The maximum observed polythionate concentration was 8μM. Thiosulfate was rather uniformly distributed throughout the pool and concentrations ranged from 35 to 45μM. Total dissolved sulfide concentrations varied with time, concentrations ranged from 16 to 48μM. Sulfate was relatively constant, with concentrations ranging from 1150 to 1300μM. The sulfur speciation of Cinder Pool is unique in that the thiosulfate and polythionate concentrations are significantly higher than for any other acid-sulfate spring yet sampled in Yellowstone National Park. Complementary laboratory experiments show that thiosulfate is the intermediate sulfoxyanion formed from sulfur hydrolysis under conditions similar to those found in Cinder Pool and that polythionates are formed via the oxidation of thiosulfate by dissolved oxygen. This last reaction is catalyzed by pyrite that occurs as a minor constituent in the sulfur spherules floating on the pool's surface. Polythionate decomposition proceeds via two pathways: (1) a reaction with H2S, yielding thiosulfate and elemental sulfur; and (2) by disproportionation to sulfate and thiosulfate.This study demonstrates that the presence of a subaqueous molten sulfur pool and sulfur spherules in Cinder Pool is of importance in controlling the pathways of aqueous sulfur redox reactions. Some of the insights gained at Cinder Pool may be relevant to acid crater lakes where sulfur spherules are observed and variations in polythionate concentrations are used to monitor and predict volcanic activity.

Mineralogy of ohyunuma explosion crater lake, Hokkaido, Japan. Part 1 : Geochemistry, hydrology, and bulk mineralogy

Lake Ohyunuma, which is an active explosion crater lake located at Noboribetsu Spa of southwest Hokkaido, Japan, has been investigated to elucidate the dynamics of clay formation processes under the acid hydrothermal conditions. The Ohyunuma lake water is characterized by distinct stratification of temperature and chemicals forming two layers. The upper layer water is relatively low-temperature (about 40°C), low-salinity, oxidized, sulfate-rich, chloride-poor acid (pH 2.4) solution, whereas the lower layer water is relatively high-temperature (max. 121°C), high-salinity, sulfide and chloride-rich acid (pH 2.7) solution. The distribution of minerals constituting the lake sediments is controlled by many factors such as location of discharge points, transportation by river waters, lake bottom topography, and flow rate and direction of lake water, in addition to in situ dissolution and precipitation processes of the minerals. Based on the lines of evidence such as calculations of saturation indexes and examinations by XRD, TEM, and AFM, the origin of the minerals was inferred as follows: elemental sulfur and pyrite are precipitated through the entire water column of Lake Ohyunuma involving both the upper and lower layer waters; the portions of them are also derived from the molten sulfur pool filled in the high temperature vent sites, associating with turbulent discharges. Alunite is precipitated in the lower layer waters and also formed locally in the upper layer waters by mixing of more acid stream and discharge waters which contain much more Al and sulfate ions. Smectite is of allogenic origin as it is mostly derived from the surrounding altered rocks, and the exchangeable cation composition deduced from the bulk sediment data is a function of temperature and solution composition. Kaolinite and halloysite may be initially translocated from the surrounding altered rocks and then they are undergoing dissolution during settling of the particles in the upper layer waters, but the dissolved materials are recrystallized as kaolinite in the lower layer waters. Most of silica minerals such as quartz, α-cristobalite, and tridymite are of allogenic origin. Diagenetic modification of the minerals with burial is not significant through the sediment column (0-67 cm depth) recovered in the present study.

Formation and Oxidation of Sulfides on Pure Iron and Iron Oxides

Formation of pyrophoric iron sulfide (PIS) on the inside-walls of molten sulfur, crude oil or asphalt tanks is the problem to be solved to avoid accidental explosions in petroleum industries. In this study, pure Fe, Fe304 and Fe 2 O 3 were sulfidized in Ar-H2S atmosphere, and the sulfidized products formed were observed and analyzed. Furthermore, sulfidized specimens were oxidized in Ar-O 2 atmosphere to study their oxidizing behavior. Sulfide formed on pure Fe was a dense and uniform film of FeS. On the contrary, sulfide films formed on Fe 3 O 4 and Fe 2 O 3 were porous FeS 2 . Oxidation of FeS 2 formed on iron oxides occurred rapidly, while oxidation rate of FeS formed on iron was much slower. The experimental results suggest that FeS 2 formed on iron oxides may act as a PIS.

Sub-aqueous sulfur volcanoes at Waiotapu, New Zealand

Exhumed, sub-aqueous sulfur mounds occur in the Waiotapu geothermal area, New Zealand. The extinct mounds are <2 m high and composed of small (<0.5 cm) hollow spheres, and occasional teardrop-shaped globules. They are located within a drained valley that until recently was connected to Lake Whangioterangi. They were formed a maximum of 820±80 years BP as a result of the rapid sub-aqueous deposition of sulfur globules, formed when fumarolic gases discharged through molten sulfur pools. Similar globules are now being formed by the discharge of fumarolic gases through a sub-aqueous molten sulfur pool in Lake Whangioterangi.

Volcanogenic Sulfur on Earth and Io: Composition and Spectroscopy

The causes of Io's variegated surface, especially the roles of sulfur, and the geochemical history of sulfur compounds on Io are not well understood. Suspecting that minor impurities in sulfur might be important, we have investigated the major and trace element chemistry and spectroscopic reflectance of natural sulfur from a variety of terrestrial volcanic–hydrothermal environments. Evidence suggests that Io may be substantially coated with impure sulfur. On Earth, a few tenths of a percent to a few percent of chalcophile trace elements (e.g., As and Se) comonly occur in sulfur and appear to stabilize material of yellow, brown, orange, and red hues, which may persist even at low temperatures. Percentage levels of chalcophile impurities are reasonably expected to occur on Io in vapor sublimate deposits and flows derived from such deposits. Such impurities join a host of other mechanisms that might explain Io's reds and yellows. Two-tenths to two percent opaque crystalline impurities, particularly pyrite (FeS 2), commonly produces green, gray, and black volcanic sulfur on Earth and might explain areas of Io having deposits of these colors. Pyrite produces a broad absorption near 1 μm that gradually diminishes out to 1.6 μm—similar but not identical to the spectrum of Io seen in Galileo NIMS data. Percentage amounts of carbonaceous impurities and tens of percent SiO 2 (as silicates) also strongly affect the spectral properties of Earth's sulfur. Io's broad absorption between 0.52 and 0.64 μm remains unexplained by these data but could be due to sodium sulfides, as suggested previously by others, or to As, Se, or other impurities. These impurities and others, such as P and Cl (which could exist on Io's surface in amounts over 1% that of sulfur), greatly alter the molecular structure of molten and solid sulfur. Minor impurities could impact Io's geology, such as the morphology of sulfur lava flows and the ability of sulfur to sustain high relief. We have not found any natural sulfur containing significant Na beyond that attributable to silicate inclusions. In sum, the unique physical–chemical properties of S-rich systems and the strong affinity of certain elements for S may have broad implications for the appearance, spectroscopic interpretation, and geologic processes of Io. Identification of impurities in sulfur may be helpful in tracing the geochemical evolution of surface deposits on Io. Perhaps foretelling of new areas of investigation, Cl has recently been reported in the Io torus (M. Kueppers and N. M. Schneider 1999, Eos Trans. 80, 5207), suggesting the presence on Io of either salts, such as halite, or sulfur chlorides. Further evidence of minor iogenic impurities should be sought in Io's neutral cloud and plasma torus as well as in further scrutiny of Io's reflectance spectra.

Spinifex Texture of Native Sulfur: A Cooling Product of Sulfur Flow Eruptions at Shiretoko‐Iwozan Volcano, Hokkaido, Japan

Abstract: Several native sulfur specimens, collected from Shiretoko‐Iwozan volcano, eastern Hokkaido, Japan, exhibit spinifex texture, which appears to resemble that often observed in komatiite. The spinifex texture is exhibited by yellow‐colored elongated skeletal native sulfur crystals up to 5 cm long settled in medium gray‐colored fine–grained clayey matrix. One surface of a specimen is coated by layers of micro pillow lava of native sulfur. Such specimens were rarely found as clasts or fragments around the 1936 No. 1 crater that erupted native sulfur flows, together with the most common monomineralic native sulfur fragments of native sulfur flows having pahoehoe surface and of native sulfur dikes. The elongated spinifex native sulfur crystals presently consist of aggregated polygrains of orthorhombic sulfur crystals formed through crystallo‐graphic transition from the single crystal of monoclinic sulfur initially crystallized. The spinifex texture exhibited by elongated skeletal native sulfur crystals is a product of rapid cooling of sulfur melt.Many lithic fragments of altered country rocks are present in the specimens exhibiting native sulfur spinifex texture. This suggests that segregation of the sulfur melt from the mixture of lithic fragments and sulfur melt was incomplete because the mixture was chilled before the melt segregation. Elongated skeletal native sulfur crystals may have nucleated and crystallized directly from the molten sulfur liquid. Lithic fragments mixed in the melt are supposed to have acted as nuclei for the nucleation of the native sulfur crystals. On the other hand, the most of native sulfur flows consist of monomineralic massive native sulfur with very scarce lithic fragments. Such massive monomineralic native sulfur crystallized from the supercooled, solidified amorphous sulfur. Such supercooled amorphous state may have been attained due to the lack of nuclei because of the scarcity of lithic fragments. The unique structures exhibited by native sulfur lava flow, including pahoehoe surface and spinifex texture, are due to the characteristic physical property of molten sulfur liquid, that is, low viscosity.

Structural and dynamic properties of liquid sulfur around the λ-transition

To gain a deeper understanding of the structure of liquid sulfur and the nature of the λ-transition at 159°C, we have performed inelastic neutron scattering (INS) experiments to yield the vibrational density of states of polycrystalline α- and β-sulfur and of liquid sulfur at temperatures above (170°C) and below (140°C) that of the λ-transition, T λ. The data are compared with Raman spectra taken at the same temperatures. The relative intensities of the spectral features in the solid and liquid state show a significant dependence on temperature. It is concluded that the structure of molten sulfur is not describable in terms of the occurrence of distinct stable molecules. Since the local structural and INS spectral parameters for liquid sulfur below and above the λ-transition temperature differ only slightly, it can be inferred that the difference between these two states is due to different molecular species with similar local packing properties but different thermal stabilities. A temperature-dependent dynamical equilibrium model for the liquid state seems appropriate, which might lead to a percolation transition around T λ=159°C.