Showing papers in "Reviews in Mineralogy & Geochemistry in 2011"

The Sulfur Budget in Magmas: Evidence from Melt Inclusions, Submarine Glasses, and Volcanic Gas Emissions

Abstract: The major magmatic volatile components—H2O, CO2, S, Cl, and F— play an important role in the formation, evolution, and eruption of magma. Knowledge of magmatic concentrations and fluxes of these volatiles is thus important for understanding explosive eruptive behavior of volcanoes, recycling of volatiles in subduction zones, formation of magmatic-hydrothermal ore deposits, fluxes of volcanic gases to Earth’s atmosphere, and potential climatic impacts of large volcanic eruptions. Over the past 30 years, new analytical techniques for measuring volatiles in melt inclusions and glasses from volcanic rocks and new developments in remote sensing technology used for quantifying volcanic emissions have led to major advances in our understanding of volatiles in magmatic systems and their fluxes from Earth’s mantle to the crust and hydrosphere. Sulfur plays a particularly important role in many of the processes noted above because it affects partitioning of metals into sulfide phases or vapor in magmas during crustal storage, and when released to the atmosphere, it forms sulfuric acid aerosol droplets that catalyze ozone destruction, influences other aspects of atmospheric chemistry, and blocks incoming solar radiation. In addition, S may play a role in causing oxidation of the mantle wedge above subduction zones (Kelley and Cottrell 2009). In silicate melts, the solubility behavior, activity-composition relations, and vapor-melt partitioning of S are complex due to multiple valence states and species (S2−, S6+ in melt; H2S, S2, SO2, SO3 in vapor) and the occurrence of non-volatile S-rich phases (immiscible Fe-S-O liquid, pyrrhotite, monosulfide and intermediate solid solutions, anhydrite). Sulfur dioxide (SO2) is the easiest of the main magmatic volatiles to measure in volcanic plumes using ground- and satellite-based remote sensing techniques because of its relatively high concentration in volcanic plumes relative to background values. More …

Sulfur Degassing From Volcanoes: Source Conditions, Surveillance, Plume Chemistry and Earth System Impacts

Abstract: Despite its relatively minor abundance in magmas (compared with H2O and CO2), sulfur degassing from volcanoes is of tremendous significance. It can exert substantial influence on magmatic evolution (potentially capable of triggering eruptions); represents one of the most convenient opportunities for volcano monitoring and hazard assessment; and can result in major impacts on the atmosphere, climate and terrestrial ecosystems at a range of spatial and temporal scales. The complex behavior of sulfur in magmas owes much to its multiple valence states (−II, 0, IV, VI), speciation (e.g., S2, H2S, SO2, OCS and SO3 in the gas phase; S2−, SO42− and SO32− in the melt; and non-volatile solid phases such as pyrrhotite and anhydrite), and variation in stable isotopic composition (32S, 33S, 34S and 36S; e.g., Metrich and Mandeville 2010). Sulfur chemistry in the atmosphere is similarly rich involving gaseous and condensed phases and invoking complex homogeneous and heterogeneous chemical reactions. Sulfur degassing from volcanoes and geothermal areas is also important since a variety of microorganisms thrive based on the redox chemistry of sulfur: by reducing sulfur, thiosulfate, sulfite and sulfate to H2S, or oxidizing sulfur and H2S to sulfate (e.g., Takano et al. 1997; Amend and Shock 2001; Shock et al. 2010). Understanding volcanic sulfur degassing thus provides vital insights into magmatic, volcanic and hydrothermal processes; the impacts of volcanism on the Earth system; and biogeochemical cycles. Here, we review the causes of variability in sulfur abundance and speciation in different geodynamic contexts; the measurement of sulfur emissions from volcanoes; links between subsurface processes and surface observations; sulfur chemistry in volcanic plumes; and the consequences of sulfur degassing for climate and the environment. ### Geodynamics and the geochemical behavior of sulfur The …

Sulfur Isotopes in Magmatic-Hydrothermal Systems, Melts, and Magmas

Abstract: The first studies on sulfur isotope geochemistry were performed approximately sixty years ago (e.g., Thode et al. 1949; Trofimov 1949). Since these early measurements on terrestrial and extra-terrestrial materials, S isotopes have been used to highlight and investigate several processes, such as the evolution of the solar system; the oxidation of the Earth’s atmosphere and hydrosphere; the genesis of ore deposits and fossil fuels (coal, oil, and gases); the origin and provenance of S species in different natural fluids, including groundwater, rainwater, as well as present-day and ancient marine waters (as recorded by evaporite deposits); the S isotope fractionation in bacterially-mediated processes; the impact of anthropogenic activities, for instance mining and related acid drainage; and others. The sulfur isotopic compositions of volcanic rocks, magmatic gases, and closely related hydrothermal fluids were the subject of numerous investigations. Among these, a considerable contribution was provided by Sakai and coworkers, who elucidated the importance of degassing and sulfide separation and the different effects of these processes, depending on the redox state of the melt and, in the case of degassing, of the separated magmatic gases as well. All of these applications were made possible due to the experimental and theoretical works devoted to the determination of the fractionation factors between different S-bearing species and compounds and their temperature dependence. This review is devoted to the magmatic-hydrothermal environment as a whole, focusing on active systems and their past analogues, which are represented by different types of ore deposits. Special emphasis is given to the use of S isotopes to investigate the effects of degassing and separation of sulfide and sulfate minerals from silicate melts. For the sake of clarity, we recall the meaning of the following terms:

Modeling the Solubility of Sulfur in Magmas: A 50-Year Old Geochemical Challenge

Abstract: There are myriad reasons why we wish to understand the behavior of sulfur in magmatic systems, reasons that vary from pure intellectual curiosity to possible impacts on society and its resources. Since ancient times sulfur has been associated with volcanic activity, and the role of sulfur in the formation of ore deposits has long been recognized because of the necessity of metal ores for our modern life-style (e.g., Barnes 1979; Naldrett 1989; Simon and Ripley 2011, this volume). Recently the mechanisms and quantities of sulfur freed from natural magmas have become an important environmental issue due to their potential effects on global climate change. For example, the average annual volcanic SO2 emission rate of 7.5 to 10.5 teragrams (Tg) per year (Halmer et al. 2002) may contribute 10% of the global atmospheric sulfur input (Halmer et al. 2002; Smith et al. 2004), and individual eruptive episodes can rapidly contribute gigantic sulfur loads to the atmosphere, 100’s to 1000’s of Tg, depending on the scale of the eruption (Self 2006). Such sulfur emissions can produce potentially catastrophic local and global changes (e.g., Fedele et al. 2003; Ward 2009); Courtillot and Rennes (2003) correlated the timing of flood basalts with extinction events in Earth’s history and hypothesized a causal relation. Part of the kill mechanism responsible for extinction may be volcanically derived sulfur creating anoxic oceans and another part of the mechanism may be climatic changes brought about by sulfur injection into the atmosphere (Ward 2009). Indeed, Erwin (2006) advocates that sulfur released from the eruption of the Siberian Flood basalts played a role in the end-Permian extinction. In light of the evidence that volcanic degassing is a significant source of sulfur to the atmosphere (Stoiber et al. 1987; Symonds et al. 1994; Andres …

The Role of Magmatic Sulfur in the Formation of Ore Deposits

Abstract: This chapter focuses on S in porphyry-type ore deposits, layered-mafic-intrusion-hosted ore bodies, and magmatic sulfide deposits. Porphyry-type ore deposits, e.g., Bingham Canyon, Utah, U.S.A. and Grasberg, Irian Jaya, are important hosts of Cu, Mo, Au, and Ag. Ore deposits hosted in layered mafic intrusions, e.g., the Bushveld and Stillwater complexes, contain significant quantities of Ni, Cu, Cr, Au and the platinum group elements (PGE: Pt, Pd, Rh, Re, Ir, Ru). Magmatic sulfide deposits, differentiated from layered mafic intrusions in that the former evince more clearly a role for immiscible sulfide accumulation without the possible presence of an aqueous fluid(s), e.g., Noril’sk and Voisey’s Bay, contain significant quantities of Cu, Ni, and the PGE. Allowing for some variability within any given ore deposit type, each of these types is unique in terms of the range of pressure and temperature of ore deposit formation, tectonic setting, and the compositional type(s) of parental causative magma. However, most porphyry-type ore deposits, layered-mafic-intrusion-hosted ore bodies, and magmatic sulfide deposits share the following features: 1) they are related chemically and physically to silicate magma; 2) they are the byproduct of differentiation of magma; 3) metals are hosted dominantly in sulfide minerals and the deposits can be thought of primarily as S anomalies (e.g., the Butte and Bingham Canyon porphyry ore deposits, located in Montana and Utah, U.S.A., respectively, contain 60 and 100 times, respectively, the ~20 Mt of S emitted during the 1991 eruption of Mt. Pinatubo); and 4) the metal(s) and S in each deposit type, albeit not necessarily the total quantity of S, are together derived from the same magmatic source. It is the connectivity of these commonalities that serves as the basis for this review chapter. The ubiquitous presence of S in magmatic systems is manifested in the commonly observed mass of S …

Sulfur-bearing Magmatic Accessory Minerals

Abstract: Almost all magmas contain sulfide- or sulfate-bearing phases. In most natural samples the sulfur-bearing phase is a sulfide, which typically is pyrrhotite (Fe1− x S) or pyrite (FeS2) although chalcopyrite (CuFeS2), pentlandite ((Fe,Ni)9S8), sphalerite (ZnS) or molybdenite (MoS2) may be present as well. Sulfate minerals are rare at magmatic conditions, and anhydrite (CaSO4) is the most common. Other magmatic SO4-bearing minerals include the sodalite group minerals (hauyne simplified formula: (Na,Ca)4–8(Al6Si6(O,S)24)(SO4,Cl)1–2), scapolite minerals (silvialite: (Ca,Na)4Al6Si6O24(SO4,CO3)), and S-bearing apatite (Ca5(PO4)3(F, Cl, OH)). Barite (BaSO4) has been mentioned in rare cases (Marchev 1991). Sulfur-bearing minerals usually constitute a negligible fraction of the mineral assemblage in magmatic rocks and thus can be classified as accessory minerals. The crystallization of sulfide, sulfate, and S-bearing minerals strongly depends on melt composition, temperature and pressure, and the S speciation in melt which, in turn, is strongly dependent on the prevailing oxygen fugacity (Baker and Moretti 2011, this volume; Wilke et al. 2011, this volume). Irrespectively of the low abundance of S-bearing minerals, the evolution of sulfur in magmas may be evaluated from the occurrence of sulfides and sulfates. These minerals are critical for estimating the activity of various sulfur-bearing species in magmas and can be used to constrain the oxygen fugacity and the S concentration in the melt (e.g., pre-eruptive sulfur concentration in melts). The presence of either sulfide or sulfate in silicate melt indicates that the predominant dissolved sulfur species in the melt are S2− or S6+, respectively. Typically one of these species is dominant, but there are conditions where S2− …

Distribution of Sulfur Between Melt and Fluid in S-O-H-C-Cl-Bearing Magmatic Systems at Shallow Crustal Pressures and Temperatures

Abstract: Volatile constituents dissolved in magmatic fluids control fundamental geologic processes including magma ascent, degassing, and eruption; metasomatism; and hydrothermal mineralization in the shallow crust, and volatile compounds involving sulfur are vigorous agents of these fluids. Volcanic outgassing of magmatic volatiles, including SO2 and H2S, to the atmosphere has influenced atmospheric chemistry throughout Earth’s history (Arthur 2000), and of particular importance has been the effectiveness of SO2- and H2SO4-laden stratospheric aerosols to reflect sunlight and cool Earth’s surface (Siggurdson et al. 1990; Oppenheimer et al. 2011, this volume; Wallace and Edmonds 2011, this volume). In addition, many ore metals exhibit chalcophile behavior, i.e., a strong affinity to S. As a result, magmatically sourced S that is typically present as reduced sulfide species plays an essential role in processes of generating nickel sulfide, porphyry copper-gold-molybdenum, high-sulfidation precious metal, and volcanogenic massive sulfide deposits (Hedenquist and Lowenstern 1994; Burnham 1997; Vaughan and Craig 1997; Seo et al. 2009; Simon and Ripley 2011, this volume). Crucial and poorly understood aspects common to each of these processes are determining how and when multi-component fluids exsolve, evolve, and escape from magmas and how significantly S dissolves in such chemically complex fluids. The results of hydrothermal experiments, summarized herein, provide important new insights into these processes. The silicate melt phase (herein abbreviated si-mt ) in magmas may contain variable concentrations of S, and S-isotopic data indicate that this S is mostly of magmatic origin (Rye et al. 1984; Wallace 2001). The melts of mafic and intermediate-silica-content magmas generally exhibit greater S concentrations (e.g., > several thousands of ppm S) than felsic melts (Ducea et al. 1994; Wallace and Anderson 2000; Cervantes and Wallace 2003; Metrich and Wallace …

Spectroscopic studies on sulfur speciation in synthetic and natural glasses

Abstract: Spectroscopic methods are powerful means to obtain information on the electronic or local structure of materials. By these methods, constraints can be provided on the chemical state, crystal chemistry or, in non-crystalline materials, the coordination environment or complexation of a given element. In this chapter, we focus on spectroscopic techniques that provide direct insight into the sulfur (S) species present in glasses and melts and which are applicable at the sulfur concentrations usually found in glasses (mostly below 1–2 wt%). Methods that are potentially suitable for this task are i) the wavelength analysis of X-ray emission spectra (mostly using the electron microprobe), ii) X-ray absorption spectroscopy, iii) 33S NMR and iv) Raman spectroscopy. For compounds such as sulfides or sulfates, containing S as a major component, further methods such as optical absorption spectroscopy in the UV-visible frequency range (UV-VIS) or electron spin/paramagnetic resonance (ESR or EPR) spectroscopy (e.g., Ross 1974; Wincott and Vaughan 2006) are useful. However, these two techniques provide only an indirect view on sulfur because they actually probe the cations, which are often transition metals. In compounds where S is a major component, these data also provide information on the sulfur species, because the cations are linked to S as an anion. In glasses, where S is only a minor component and cations are mostly coordinated by oxygen, it is difficult to link the observations made on the cation to the S species. Nevertheless, there are some studies on glasses where the additional information by UV-VIS or ESR spectroscopy was used to constrain possible species of sulfur in the glass (e.g., Beerkens 2003; Bingham et al. 2010). Here, only very brief introductions to the spectroscopic techniques will be provided. For a more detailed introduction to the spectroscopic techniques introduced here the reader is …

Diffusion and Redox Reactions of Sulfur in Silicate Melts

Abstract: Although large-scale transport in magmas is usually controlled by convection, diffusion of sulfur in silicate melts, nevertheless, plays a crucial role in the kinetics of various magmatic processes. The most important process is probably the degassing of magmas and melts initiated by an oversaturation of the melt with respect to dissolved volatiles. Such oversaturation can be caused in nature, i.e., by decompression when a magma ascends to the Earth surface. But the degassing of melts is also of major interest for technical applications, e.g., during fining of melts in industrial glass production. The kinetics of volcanic eruptions and the fining of glass melts are basically controlled by the dynamics of bubble nucleation and growth, and these properties are strongly affected by the diffusion of volatiles from the melt into bubbles (Nemec 1980a,b; Sparks et al. 1994; Muller-Simon 2011, this volume). Hence, understanding the diffusion of volatiles in melts provides a necessary tool for modeling bubble nucleation and growth. However, the diffusivities of volatiles such as H2O, CO2, SO2 and H2S in the melt do not only affect the degassing rate, they may also cause a fractionation of volatiles between gas phase and melt as well, due to different diffusivities. For instance, in hydrous magmas the diffusion of H2O is usually much faster than CO2 and sulfur diffusion (Baker et al. 2005; Zhang and Ni 2010), so rapid, disequilibrium removal of bubbles from the melt may cause an artificial enrichment of some components in the bubbles. Other processes which may be governed by sulfur diffusion in the melts are the dissolution and precipitation of minerals. In glass manufacturing, crucial problems are the kinetics of dissolution of the raw materials in the melt batch and of …

Experimental Studies on Sulfur Solubility in Silicate Melts at Near-Atmospheric Pressure

Abstract: Various experimental studies in silicate melts have been performed to understand the dependence of sulfur solubility on melt composition and experimental conditions. These experiments were motivated by glass technologists due to the role swulfur compounds play in fining (Muller-Simon 2011, this volume) and coloring (Falcone et al. 2011, this volume) melts. In particular, the risk of foaming in the glass tank and rejects in the glass production due to discoloration and bubbles demand a systematic approach for sulfur solubility in silicate melts. Also sulfur solubility experiments have been conducted by metallurgists, whose interest is centered on the interaction of metal and slag melts to desulfurize steel products (Lehmann and Nadif 2011, this volume). Besides technical applications, sulfur solubility experiments at atmospheric pressure are of importance to geoscientists in modelling near-surface conditions such as sulfur degassing from volcanoes (Oppenheimer et al. 2011, this volume) and the role of sulfur in the formation of ore deposits (Simon and Ripley 2011, this volume). In order to study the effect of polymerization of the silicate network on sulfur solubility, melt compositions were varied in the experiments across broad limits. It has been shown that the solubility generally increases with increasing network modifier to network former ratio (Baker and Moretti 2011, this volume). This supports the idea that the presence of free volume and cationic charge compensators in the network structure promote incorporation and mobility of anionic sulfur species (Behrens and Stelling 2011, this volume). Sulfur speciation is also responsible for the strong dependence of sulfur solubility on oxygen fugacity as reported by Baker and Moretti (2011, this volume) and Muller-Simon (2011, this volume) for natural and technical melts, respectively. Sulfur was found to be stable in these melts as sulfide S2− under reducing conditions …

The Role of Sulfur Compounds in Coloring and Melting Kinetics of Industrial Glass

Abstract: Soda-lime-silica (SLS) glass is the most widely used of all commercial types of glass. This type of glass is mainly used for manufacturing windowpanes, household glassware and glass containers (e.g. bottles, jars) for foodstuffs and beverages. These types of end-products differ in their application, and production method (e.g., blowing and pressing for containers and glassware, float process for windows) as well as in their chemical composition. Nevertheless, they are all produced by melting mixed raw materials ( batch) in a glass furnace at maximum temperatures ranging between 1500–1600 °C. The batch consists mainly of silica sand, sodium carbonate (soda), lime, dolomite and variable amounts of glass cullet. Small quantities of alumina-bearing raw materials, fining agents (e.g., sodium sulfate), coloring and reducing/oxidizing agents are also added to the batch. For the production of SLS glass, sulfur containing raw materials (e.g. sulfates and sulfides) play an important role in determining the final product’s quality. These compounds are involved in the final part of the fusion process, known as the fining process. In this process, the decomposition of raw materials generates a large amount of gas. The evolution of those gases from the glass melt is enhanced by the presence of the sulfur compound (Kloužek et al. 2007). Moreover, sulfur compounds act as oxidizing (sulfates) or reducing (sulfides) agents, playing a decisive role in the coloring mechanism of the final glass. Sulfates also enhance the kinetics of the sand’s dissolution by wetting the sand grains at relatively low temperatures thereby, accelerating the melting process (Albayrak and Sengel 2008; Muller-Simon and Gitzhofer 2008; Daneo et al. 2006, 2009). In Table 1⇓, typical composition ranges for SLS containers glasses produced in Italy are reported in wt% of oxides (data from Stazione Sperimentale del Vetro, SSV). The total sulfur concentration in …

Fining of Glass Melts

Abstract: The degassing of silicate melts plays an important role in both the Earth and glass sciences. Volcanic eruptions are driven by the expansion of exsolved volatiles. These volatiles are initially dissolved in magmas at high pressures and later released as one or more fluid phases during ascent of the magma to the Earth’s surface due to decompression (Webster and Botcharnikov 2011, this volume; Oppenheimer et al. 2011, this volume). During fining of glass melts the oversaturation of the silicate liquid with respect to dissolved volatiles is induced by heating. Although the process of volatile oversaturation occurring in geologic and industrial melts differs, the fundamental mechanisms controlling melt degassing are similar in both cases, particularly with respect to the nucleation and growth of gas bubbles in the melt and their upward migration driven by buoyancy. Another similarity of natural and technical melt degassing is the role of sulfur. Tremendous amounts of sulfur in form of SO2 and H2S are produced by volcanic eruptions at the surface or by the cryptic degassing of magmas ascending through the earth’s crust (see Oppenheimer et al. 2011, this volume). During the fining of industrial glass melts, one takes advantage of the solubility behavior of sulfur in silicate melts. Sulfate added to the melt batch as a raw material, decomposes to release gaseous compounds during fining that enhance the expansion of existing bubbles which can, as a result, ascend more readily to the melt surface. Hence, the release of gaseous sulfur dioxide is a major issue in both volcanic eruptions and industrial glass production. In this chapter we will have a detailed look at the process of fining in industrial mass glass production. Glassproductsarefoundinwidefieldsofdailylife,suchasautomotiveglazing,architecture, food and pharmaceutical packaging, and optical devices or opto-electronic components in computers and consumer electronics. The …

Analytical Methods for Sulfur Determination in Glasses, Rocks, Minerals and Fluid Inclusions

Abstract: The analytical techniques that are normally utilized to determine the concentration of sulfur in geologic materials can be divided into bulk analytical methods that require sample powders and microanalytical methods done in situ . The most common method of bulk sulfur analysis is accomplished using combustion methods followed by detection of SO2 in an infrared cell. A similar method involves an elemental analyzer coupled to a mass spectrometer where the mass 64 ion beam is monitored and compared to a standard. X-ray fluorescence is another method of bulk powder analysis that is well established for the determination of sulfur in coal and plant materials, but is only rarely used for the analysis of rocks due to a relatively high detection limit and difficulties with sample fusion. Micro-analytical techniques normally involve individual minerals or glasses. The most commonly used method is electron microprobe analysis (EMPA), but ion microprobe (SIMS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) methods are useful for some samples. Nuclear methods of sulfur analyses are useful for some materials largely because of their very low detection limits. A relatively new technique is the application of LA-ICP-MS to determine the concentration of sulfur in fluid inclusions contained within glasses and minerals. In this chapter we review how these methods may be used to measure the concentration of sulfur in a variety of geologic materials. We emphasize the types of materials that can be analyzed, sample preparation, standardization techniques, detection limits and uncertainties that are associated with each of the methods. Elsewhere in this volume, the determination of sulfur species in glasses is discussed (Chapter 2 -- Wilke et al. 2011) and methods of isotopic analyses are treated (Chapter 15 -- Marini et al. 2011). ### Total sulfur concentration in minerals, rocks and glasses using elemental analyzer – infrared absorption technology Automated, high-temperature combustion, carbon-sulfur analyzers utilize solid state infrared (IR) absorption for the …

Sulfur in Extraterrestrial Bodies and the Deep Earth

Abstract: This chapter reviews the origin and fate of sulfur (S) in silicate melts in the solar system, experiments bearing on the role of S in element partitioning among melts and solids in planets, and finally our current understanding of silicate melts and the role of sulfur in planetary evolution. Sulfur is an important component of undifferentiated meteorites that are precursors to planets. When planetary bodies differentiated into cores and mantles, metal and/or sulfides were removed from silicates. This process can be traced. Then, iron-sulfide cores differentiated into metal and metal-sulfide fractions, some of which are preserved as iron meteorites. The iron meteorites probably fractionated from silicate mantles at much lower pressures than the cores of Earth or Mars. Understanding the role of sulfur in silicate melts is critical to unraveling the history of Earth, the terrestrial planets, and the differentiated asteroids that were once parts of early planetesimals. ### Silicate melts and sulfur in primitive source materials Primitive extraterrestrial samples available for laboratory study include 1–20 μm cometary grains collected by the United States’ (NASA) Stardust mission, asteroidal material collected by the Japanese (JAXA) Hyabusa mission, interplanetary dust particles (IDPs) collected from the stratosphere by airplanes, micrometeorites from various collection sites, and meteorites that fall to Earth and are recovered. Sources of primitive meteorites are parent bodies, primarily asteroids, that did not differentiate into silicate mantles and metal-rich cores. The oldest dated solar system rocks are not bulk meteorites, but are the high-temperature, melted components of undifferentiated meteorites, which are a kind of cosmic sedimentary rock. These “chondritic” meteorites are slightly younger than the components that accreted to form them. They have atomic ratios of rock-forming elements (e.g., Fe/Si) that are very similar to those measured in the solar photosphere using spectroscopy. The “primitive” nature of meteorites is established by their radiometric ages, and their lack of aqueous and …

Interactions Between Metal and Slag Melts: Steel Desulfurization

Abstract: Knowledge of the partitioning behavior of sulfur between molten metals and silicates is of interest for understanding processes in the early solar system and in the deep Earth at the mantle/core boundary, but also in technical applications such as the production and purification of steel. Thermodynamic aspects relevant to processes in the Earth and in the early solar system are presented by Baker and Moretti (2011) and Ebel (2011) of this review volume. Here we focus on interactions between molten metals and slags which are the basis for desulfurization of molten metals during steel production. Desulfurization is an important step in the refining of high-quality steels for various applications. The production of liquid steel can be described schematically as follows. Steel can be produced directly from iron ore which is reduced to hot metal in a blast furnace (BF) or by melting scraps in an electric arc furnace (EAF). The hot metal is transformed into steel by oxidizing dissolved carbon in a basic oxygen furnace (BOF). During this process, the phosphorus content is reduced as well. Before the BOF operations, a first desulfurization is performed in the transfer vessel from BF to BOF. After scrap melting or refining in the BOF, steel is “tapped” in a ladle for secondary steelmaking operations, i.e., further decarburization (especially for Ultra-Low Carbon steels), deoxidation (to reduce the oxygen content), alloying (to reach the target composition) and further desulfurization, if needed. In solid steel, sulfur is mainly present as manganese sulfide (MnS) inclusions. MnS inclusions affect the processing and properties of steel. Their volume fraction, size, shape and distribution depend on many factors. The most important factors are the S-content, the solidification rate, the degree of hot and cold deformation and the hot working temperatures. Since the inclusions are more plastic than steel, they act …

Studies of Sulfur in Melts – Motivations and Overview

Abstract: ### Background For the past 37 years the Mineralogical Society of America, and in conjunction with the Geochemical Society (since 2000), have sponsored and published 72 review volumes that communicate the results of significant advances in research in the Earth sciences. Several of these have either directly or indirectly addressed the fundamental importance, role, and behavior of volatile components on processes influencing magma rheology, crystallization, evolution, eruption, and related metasomatism and mineralization. Volume 30—which was published in 1994—focused on this topic broadly, and this volume has provided a lasting summary on the geochemical and physical behaviors of a wide variety of magmatic volatiles (Carroll and Holloway 1994). Since that year, continued research has brought important and new knowledge about the role of the volatile component sulfur in natural magmas, and significant progress was made simultaneously in understanding the role of sulfur in industrial or technical processes such as glass or steel production. Here, in volume 73, we have assembled in 15 chapters the current state of research concerning sulfur in melts based on the extensive experience of various authors practically working on these topics. The behavior of sulfur in melts and its implications for natural and industrial processes are still insufficiently understood, and hence, are difficult to apply as a tool for interpreting problems of geological or industrial interest. In recent decades, various new investigations in the geosciences as well as in the engineering and material sciences have employed modern spectroscopic, analytical, theoretical, and experimental techniques to improve our understanding of the complex and volatile behavior of sulfur in a wide variety of molten systems. However, these different research initiatives (e.g., empirical vs. applied research and natural vs. technical applications) were rarely well integrated, and the scientific goals were usually approached with specific and relatively focused points of view. Consequently, bridging this …