Concentration In Melt Research Articles

THERMODYNAMICS OF OXYGEN SOLUTIONS IN BORON-CONTAINING Fe – Ni MELTS

Fe – Ni alloys are widely used in modern technology. Boron is one of the alloying components in these alloys. Oxygen is one of the harmful impurities in Fe – Ni alloys, it presents in the metal in dissolved form or in the form of oxide nonmetallic inclusions. The presence of oxygen in these alloys degrades their service properties. The study of thermodynamics of the oxygen solution in boron-containing Fe – Ni melts is of considerable interest for the practice of such alloys production. Thermodynamic analysis of oxygen solutions in boroncontaining Fe – Ni melts has been carried out. The equilibrium constant of interaction of boron and oxygen dissolved in the Fe – Ni melts, the activity coefficients at infinite dilution, and the interaction parameters characterizing these solutions were determined for melts of different composition. In the interaction of boron with oxygen in Fe – Ni melts, the oxide phase, in addition to B2 O3 , contains FeO and NiO. Values of the mole fractions of B2 O3 , FeO and NiO in the oxide phase for different boron concentrations in Fe – Ni melts were calculated at 1873 K. In the case of an iron melt at low boron contents, the mole fraction of boron oxide is ~0.1. As the content of nickel and boron increases in the melts, the mole fraction of boron oxide in the oxide phase increases and, in the case of pure nickel, is close to unity. Dependences of the oxygen solubility on the contents of nickel and boron in the studied melts were calculated. With increasing nickel content in melt deoxidation ability of chromium increases significantly. The oxygen solubility curves in boron-containing Fe – Ni melts pass through a minimum whose position shifts to the higher boron content with an increase in the nickel content in melt. Boron contents in minimum points on the oxygen solubility curves and the corresponding minimum oxygen concentrations were determined.

Experimental calibration and implications of olivine-melt vanadium oxybarometry for hydrous basaltic arc magmas

The strong dependence of vanadium partitioning between olivine and silicate melt (DVO1-M) on redox conditions (fO2) can be used as sensitive oxybarometer in magmatic systems. Here we extend the experimental database on DVO1-M, obtained so far at high temperatures (mainly above 1250 °C), to lower temperatures that are typical for island-arc basalts. Crystallization experiments were performed using a composition from Mutnovsky volcano (Kamchatka), and the investigated temperature, pressure, and oxygen fugacity ranges were 1025–1150 °C, 0.1 and 0.3 GPa, and ΔQFM of –0.5 to +3.2, respectively. The water content in melts ranged from 0.6 to ~6.5 wt% H2O. The data demonstrate a strong negative correlation between DVO1-M and oxygen fugacity, similar to the behavior observed previously at higher temperatures and in MgO-rich compositions. The correlation between DVO1-M and ΔQFM in the range from –0.5 to +3.2 is described for melts with MgO < 12 wt% and Na2O < 4 wt% at temperatures ≤1250 °C by the empirical equation: ΔQFM = −3.07−0.29+0.26log⁡DVO1-M−3.34−0.49+0.40 with the standard error (SE) as a function of log DVO1-M: 2SE(ΔQFM) = –0.275log DVO1-M + 0.4.

Петрология Ялуниногорского гранитоидного массива (Алапаевско-Сухоложская медно-порфировая зона, Средний Урал)

Yaluninogorsk quartz diorite-trondhjemite massif is situated in Alapaevsk-Sukhoy Log zone of Eastern-Ural High potentially productive for Cu (±Mo) porphyry type of mineralization. The massif is a magma chamber 3 × 2 km under central type volcano. The rocks of massif frame are transformed into propylites, sometimes intensively sulfidized. In this regard the massif is considered as an ore-forming. Petrological study of Yaluninogorsk massif shows, that is formed by holocrystalline rocks of meso-abyssal facies, varying from quartz-gabbro-diorites to tonalities, accompanied by veined trondhjemites. Early mineral phases of quartz diorites consist of augite, basite plagioclase An 70-50 , titanomagnetite. Late phases are represented by acid plagioclase An 30-25 , quartz, titanomagnetite, biotite, magnesiohornblende, which substitutes pyroxene. Crystallization process of quartz diorites and trondhjemites occurred under isobaric conditions with 1.5-2.0 kbar and a slow cooling. Crystallization temperature exceeded 900°C for the early phases, and 800-720°С for the late phases. The initial melts can be characterized as having low water content. Their oxidation rate was ΔNNO = 0.5-0.8. Residual melts with trondhjemite composition contained about 3.5-4.0 wt % H 2 O under P gen = P H2O . Deep erosion of the volcano together with low water content of the initial melts are likely to be negative factors for the discovery of industrial porphyry-type ore deposits associated with Yaluninogorsk massif. The study of post-magmatic transformations of rocks from the massif and its environs revealed the presence of no industrial significance skarns with magnetite-chalcopyrite-pyrite mineralization, accompanied by nickel sulfides and nickel sulfoarsenides; veined carbonate-quartz-chlorite metasomatites with chalcopyrite mineralization, containing selenium-bearing sulfosalts and Ag, Cu, Bi tellurides.

Research on Melt Degassing Processes of High Conductivity Hard Drawn Aluminum Wire

Degassing effects of ultrasonic and vacuum processes on high conductivity hard drawn aluminum melt were studied. Results showed that the degassing efficiency improved with the increase of ultrasonic power within certain range, stabilizing at 70% with 240W. For vacuum degassing process, hydrogen content of aluminum melt decreased with the loading time and was linear with logarithm of vacuum degree. Comparison of degassing effects of ultrasonic, vacuum, vacuum-ultrasonic degassing process showed that vacuum-ultrasonic process presented optimal effect.

Coupling of Redox Conditions of Mantle Melting and Copper and Sulfur Contents in Primary Magmas of the Tolbachinsky Dol (Kamchatka) and Juan de Fuca Ridge (Pacific Ocean)

The compositions of parental melts of Tolbachinsky Dol (Kamchatka) basalts were estimated from the compositions of olivine-hosted (Fo90.5-83.1) primitive melt inclusions in the rocks of the Northern breakthrough of the Great Tolbachik Fissure Eruption (1975 A.C.) and of the late-Holocene cone “1004”. The parental melts contain 100–150 ppm Cu and 0.16–0.30 wt % S. These concentrations are much higher than those determined for the initial magmas of mid-ocean ridge basalts (MORB), for example of the Juan de Fuca ridge (Cu = 55–105 ppm, S=0.09–0.12 wt %). Modeling of mantle melting under variable redox conditions demonstrated that the high Cu and S contents in the Tolbachinsky Dol melts can be obtained by 6–12% melting of DMM-like source under oxidized conditions (ΔQFM = +1.2 ± 0.1) and do not require a significant (>30–35% for S) subduction-related influx of these elements to the mantle source. The high contents of Cu and S in the Tolbachinsky Dol melts are largely explained by the increase of sulfide solubility in a silicate melt under oxidized conditions. In contrast, relatively reduced (ΔQFM ∼ 0) conditions of MORB generation result in low contents of Cu and S in their initial magmas. The estimated ΔQFM values agree well with the data obtained using the Cr-spinel–olivine oxybarometer. The high oxygen potential of Tolbachinsky Dol primary magmas is inherited by more evolved magmas, thus favouring Cu enrichment up to 270 ppm during magma fractionation, approaching maximum copper contents in the global systematics of island-arc rocks.

Formation of A-type granites in the Lower Yangtze River Belt: A perspective from apatite geochemistry

Apatite is ubiquitous in A-type granites, and can be used to elucidate the volatile contents of the silicate melt, which reflect its source characteristics. A-type granites have been recognized as a distinct group of granites. A1- and A2-type subgroups are produced under different extensional settings. However, the details of the mechanisms behind the distinctive geochemical characteristics of A1- and A2-type granites remain obscure. Belts of Cretaceous A1- and A2-type granites occur along the Lower Yangtze River Belt in eastern China. Here we investigated the major and trace element compositions of apatites from contemporary A1- and A2-type granites at different localities along the Lower Yangtze River Belt, in order to decipher their discrepant source processes. Apatites from A1- and A2-type granites show similar major and trace elements, but differ in their F and Cl concentrations. Apatites from A1-type granites in the eastern part of the Lower Yangtze River Belt have much lower F and higher Cl concentrations compared to A2-type granites in the western part. Moreover, from the east to the west, the F concentrations of apatites from A1-type granites increase, while the Cl concentrations decline. In a subducted plate, F is retained by amphibole, chlorite, serpentine and mica minerals through the amphibolite stage, and finally by phengite and lawsonite during the eclogite stage, whereas, Cl is controlled by amphibole, chlorite and serpentine. The high and varied Cl concentrations in A1 subgroup apatites, therefore, may be attributed to the breakdown of amphibole, chlorite and/or serpentine decomposition during partial melting of subducted oceanic crust releasing a large amount of Cl at shallower depth. In contrast, F is transported to deeper depths in the subducted oceanic crust, and released through breakdown of phengite and lawsonite, making an important contribution to the formation of A2-type granites. Apatites from A1- and A2-type granite samples show regular changes in LREE/HREE, LREE/MREE and MREE/HREE ratios with increasing distance from the location of the subduction zone, probably as the result of nonsynchronous dehydration of the serpentine and phengite at different stages during subduction. We propose that A1- and A2-type granites on the Lower Yangtze River Belt were derived from sources metasomatised by fluids originating from the breakdown of amphibole, chlorite and/or serpentine with higher Cl, lower F, and from phengite and/or lawsonite with relatively higher F but lower Cl, respectively.

Spinels of Variscan olivine hornblendites related to the Montnegre granitoids revisited (NE Spain): petrogenetic evidence of mafic magma mixing

Olivine hornblendites (cortlandtites) form part of the Montnegre mafic complex related to late-Variscan I-type granitoids in the Catalan Coastal Ranges. Two generations of spinel are present in these hornblendites: Spl1 forms euhedral crystals included in both olivine and Spl2. Spl2 forms euhedral to anhedral crystals associated with phlogopite and fibrous colourless amphibole forming pseudomorphs after olivine. Compositions of Spl1 are picotite-Al chromite (Fe#: 77.78-66.60; Cr#: 30.12-52.22; Fe3+/R3+: 6.99-21.89; 0.10< TiO2%<0.62). Compositions of Spl2 are pleonaste (Fe#: 37.86-52.12; Cr#: 1.00-15.45; Fe3+/R3+: 0.31-5.21; TiO2%<0.10). The two types of spinel follow a CrAl trend, mainly due to the substitution (Fe2+)-1Cr-1= MgAl, which is interpreted as the result of mixing between two different mantle-derived melts. The compositions of early Spl1 crystals included in olivine are characteristic of Al-rich basalts. More aluminous Spl2 would result from reaction of olivine with a less evolved, Al and K-rich mantle-derived melt after new refilling of the magma chamber or channel. As a whole, spinels from similar examples of Variscan olivine hronblendites also follow a CrAl trend with high Fe# and starting at higher Cr# than other trends of this type. Cr# heterogeneity in the early spinels from these Variscan hornblendites would be inherited from the variable Al content of the mafic melts involved in their genesis.

Melt inclusion constraints on volatile systematics and degassing history of the 2014–2015 Holuhraun eruption, Iceland

The mass of volatiles emitted during volcanic eruptions is often estimated by comparing the volatile contents of undegassed melt inclusions, trapped in crystals at an early stage of magmatic evolution, with that of the degassed matrix glass. Here we present detailed characterisation of magmatic volatiles (H2O, CO2, S, Fl and Cl) of crystal-hosted melt and fluid inclusions from the 2014–2015 Holuhraun eruption of the Barðarbunga volcanic system, Iceland. Based on the ratios of magmatic volatiles to similarly incompatible trace elements, the undegassed primary volatile contents of the Holuhraun parental melt are estimated at 1500–1700 ppm CO2, 0.13–0.16 wt% H2O, 60–80 ppm Cl, 130–240 ppm F and 500–800 ppm S. High-density fluid inclusions indicate onset of crystallisation at pressures ≥ 0.4 GPa (~ 12 km depth) promoting deep degassing of CO2. Prior to the onset of degassing, the melt CO2 content may have reached 3000–4000 ppm, with the total magmatic CO2 budget estimated at 23–55 Mt. SO2 release commenced at 0.12 GPa (~ 3.6 km depth), eventually leading to entrapment of SO2 vapour in low-density fluid inclusions. We calculate the syn-eruptive volatile release as 22.2 Mt of magmatic H2O, 5.9–7.7 Mt CO2, and 11.3 Mt of SO2 over the course of the eruption; F and Cl release were insignificant. Melt inclusion constraints on syn-eruptive volatile release are similar to estimates made during in situ field monitoring, with the exception of H2O, where field measurements may be heavily biased by the incorporation of meteoric water.

Melt holding time as an important factor on the formation of quasicrystal phase in Mg67Zn30Gd3 alloy

In the present work, the content of icosahedral quasicrystal phase (I-phase) and melt holding time shows a mono peak curve: a small amount of I-phase and lots of Mg3(Gd,Zn) phase are presented for t < 21 min, however a great deal of I-phase is observed for t > 21 min, and the volumetric fraction of I-phase has the maximum of 49.50% for t = 41 min. This strategy of formation of quasicrystal phase makes us realize that melt thermal treatment could significantly affect the phase types in MgZnGd alloy.

Formation of Metallic Phase on Reducing-Gas Injection in Multicomponent Oxide Melt. Part 3. Separation of Ferronickel and Oxide Melt

Using the equations of physicochemical hydrodynamics and experimental results regarding the surface and interphase properties of metallic and oxide melts, the conditions in which metallic phase is formed in the bubbling of carbon monoxide through molten oxidized nickel ore are described. The critical dimensions of the gas bubble (Rb.cr) and the metal droplet (rd.cr) moving in oxide melt without change in size are determined in the range 1550–1750°C. It is found that Rb.cr increases slightly from 6.35 × 10–2 m at 1550°C to 6.58 × 10–2 m at 1750°C. With change in the droplet composition and the temperature, rd.cr varies from 2.1 × 10–3 to 2.9 × 10–3 m. The dimensions of the metal droplet formed at a single bubble during the reduction of nickel and iron from oxide melt are determined. As the content of nickel and iron oxides in the melt decreases with increase in the overall CO consumption, the nickel content in the ferronickel droplets falls from 89 to 18%, while the droplet diameter decreases from 1.4 × 10–3 to 8.0 × 10–4 m. The droplet mass falls correspondingly from 9.4 × 10–5 to 1.6 × 10–5 kg. The conditions in which the bubble–droplet system rises through the melt are determined. Over the whole range of temperature and Ni content, the bubble–droplet system begins to rise through the oxide melt when rd/Rb is less than 0.68–0.78. To assess the stability of the bubble–droplet system, with the given bubble and droplet dimensions, the parameters determining their joint motion are calculated. It is found that breakaway of the metal droplet from the bubble is not possible in pyrometallurgical systems. The formation of metal phase as a result of the bubbling of carbon monoxide through the oxide melt is described. In this process, the interaction of the oxide melt with the gas is accompanied by the formation of metal droplets, which become attached to the surface of gas bubbles and move to the surface of the oxide melt. Metal with 80–90% Ni is formed at first. With decrease in the nickel content in the oxide melt, its content in the metal declines to 20%. At the surface of the oxide melt, the metal droplets coalesce. When their diameter is greater than 5 × 10–3 m, they break away from the surface and fall to the bottom. If the falling drop collides with ascending bubble–droplet systems, they may coalesce with it or flow around it. On coalescence, the small droplets will be assimilated and rise to the surface. The breakaway force of the droplet from the bubble significantly exceeds the gravitational force on the droplet. Therefore, the bubble–droplet system is stable for all the size ratios considered.

On the development of the calc-alkaline and tholeiitic magma series: A deep crustal cumulate perspective

Two distinct igneous differentiation trends – the tholeiitic and calc-alkaline – give rise to Earth's oceanic and continental crust, respectively. Mantle melting at mid-ocean ridges produces dry magmas that differentiate at low-pressure conditions, resulting in early plagioclase saturation, late oxide precipitation, and Fe-enrichment in mid-ocean ridge basalts (MORBs). In contrast, magmas formed above subduction zones are Fe-depleted, have elevated water contents and are more oxidized relative to MORBs. It is widely thought that subduction of hydrothermally altered, oxidized oceanic crust at convergent margins oxidizes the mantle source of arc magmas, resulting in erupted lavas that inherit this oxidized signature. Yet, because our understanding of the calc-alkaline and tholeiitic trends largely comes from studies of erupted melts, the signals from shallow crustal contamination by potentially oxidized, Si-rich, Fe-poor materials, which may also generate calc-alkaline rocks, are obscured. Here, we use deep crustal cumulates to “see through” the effects of shallow crustal processes. We find that the tholeiitic and calc-alkaline trends are indeed reflected in Fe-poor mid-ocean ridge cumulates and Fe-rich arc cumulates, respectively. A key finding is that with increasing crustal thickness, arc cumulates become more Fe-enriched. We propose that the thickness of the overlying crustal column modulates the melting degree of the mantle wedge (lower F beneath thick arcs and vice versa) and thus water and Fe3+ contents in primary melts, which subsequently controls the onset and extent of oxide fractionation. Deep crustal cumulates beneath thick, mature continental arcs are the most Fe-enriched, and therefore may be the “missing” Fe-rich reservoir required to balance the Fe-depleted upper continental crust.

Effect of Trace O Element on High-temperature Wettability Between Ni3Al Melt and Y2O3 Ceramic

Effect of trace O element on the high-temperature wettability between Ni3Al scrap melt and Y2O3 ceramic at 1873 K is investigated. With the increase in O content in Ni3Al scrap melt from 6 to 21 ppm, the equilibrium contact angle decreases from 93.3° to 88.9°. The initial surface tension and adhesive work of molten Ni3Al scrap drop from 3153.5 to 807.4 mN m−1 and from 2974.6 to 882.2 mN m−1, respectively. The average spreading rate increases from 0.03° s−1 to 0.17° s−1. The whole wetting processes are divided into four periods. The main driving force for spreading in period (1) is the adsorption and diffusion of active atoms around the interface. Trace O content in Ni3Al scrap has a significant impact on interfacial reactions which mostly take place in the second stage, and can accelerate the spreading process on Y2O3 substrate. The reaction products during wetting process are Y3Al5O12, YAlO3 and Al2O3.

Phase relations in the Cabeza de Araya cordierite monzogranite, Iberian Massif: implications for the formation of cordierite in a crystal mush

Experimental investigations and thermodynamic calculations of the phase relations of a cordierite-rich monzogranite from the Cabeza de Araya batholith (Caceres, Spain) have been performed to understand the formation of cordierite. The experiments failed to crystallize cordierite in the pressure range 200-600MPa, in the temperature range 700-975oC and for different water activities (melt water contents between 2 and 6 wt.%). In contrast, clinopyroxene and orthopyroxene (absent in the natural mineral rock assemblage), together with biotite, were observed as ferromagnesian assemblage in a wide range of experimental conditions. Thermodynamic calculations, using the software PERPLE_X, describe the formation of cordierite only at 200 and 400MPa and very low water contents, and the amount of cordierite formed in the models is always below 3.5 vol.%. The results indicate that cordierite is not in equilibrium with the bulk rock compositions. The most probable explanation was that cordierite nucleated and crystallized from a melt that is not in equilibrium with part of the mineral assemblage present in the magma. This “non-reactive” mineral assemblage was mainly composed of plagioclase. The silicate melts from which cordierite crystallized was more Al-rich and K-rich than the silicate melt composition in equilibrium with the bulk composition. One possible process for the high Al content of the silicate melt is related to assimilation and partial melting of Al-rich metasediments. An exo-perictetic reaction is assumed to account for both textural and geochemical observations. On the other hand, hybridization processes typical for calc-alkaline series can also explain the high proportions of “non-reactive” minerals observed in relatively high temperature magmas. This study clearly demonstrates that silicate melts in a crystal mush can depart significantly from the composition of melt that should be in equilibrium with the bulk solid assemblage.

Fluid and Melt Inclusions from Subvolcanic to Surface Environment in the Campi Flegrei (Napoli, Italy) Active Volcanic System

ABSTRACT We present a summary of the results obtained on more than 25 years of research achieved on Campi Flegrei (CF) past eruptions, focusing our attention on the role played by fluids in the magmatic system based on fluid (FI) and melt inclusions (MI). Particularly FI and MI data from subvolcanic igneous systems in the CF area provide valuable information on the nature of fluid and melt phases trapped during the late evolutionary stages of the alkaline magmatic systems. They also document liquid immiscibility at pre-eruptive magma conditions and furnish evidence of high salinity fluids (brines) exsolving directly from magma in the upper part of the plumbing system at the magmatic/hydrothermal transition and playing critical roles in ore metal transport. CF volcanic system can be interpreted as representing a modern analogue of low sulfidation epithermal deposits or a porphyry copper system. This interpretation led to the formulation of a model to explain ground movements (bradyseism) in the CF. Finally new finding for the estimations of pre-eruptive volatile contents in CF through MI are discussed. MI are the only direct samples to measure volatile contents of undegassed melt at sub-volcanic conditions. Since the depth of formation of MI is estimated using H2O-CO2-silicate melt solubility models, it is important to emphasize that, to obtain a more accurate measure of the pre-eruptive CO2 concentration, not only the CO2 in the glass but also in the bubble have to be measured otherwise the minimum CO2 content in MI is obtained.

Tektites and microtektites iron oxidation state and water content

Fe redox and water content of impact melt are important parameters as they can greatly affect melt density and viscosity which, in turn, are important parameters greatly affecting the melt evolution and fate. In this manuscript I briefly describe recent research on X-ray absorption spectroscopy (XAS) determination of Fe oxidation state and micro Fourier transform infrared spectroscopy (FTIR) determination of water content putting them in the context of previous research done with different techniques. In comparison with other techniques requiring large amount of samples (e.g. potassium dichromate titration, Mossbauer spectroscopy, Karl Fischer titration), XAFS and micro FTIR techniques allow to study both macroscopic samples of tektites as well as smaller microtektites giving the same error, making it possible to compare results between tektites and micro-tektites and, consequently, also to find differences between tektites and microtektites or between microtektites from different strewn fields. A brief introduction on impact cratering and melt formation during impact events is aimed to introduce the subject to non specialised readers.

The effect of fluorine and chlorine on trace element partitioning between apatite and sediment melt at subduction zone conditions

The effect of F and Cl on trace element recycling during subduction-related sediment melting has been investigated by performing piston-cylinder experiments with a hydrous experimental pelite starting material (EPSM) with variable Cl (~0, 500, 1000, 2000, or 3000ppm) and F (~0, 700, or 1500ppm) concentrations, at 2.5GPa, 800°C. The variations of trace element concentrations in melt are systematically correlated with the variation of F (0.07–0.39wt%) and Cl (0.07–0.39wt%) contents. Trace elements Zn, V and Pb, and major elements Fe, Mg and Ca, show positive correlations with each other, and also with the Cl content in melt. The concentrations of light and medium rare earth elements (LMREE) increase with the Cl content in melt, whereas both F and Cl cause a decrease in the concentrations of high field strength elements (HFSE, such as Nb, Ta, Zr and Hf). Trace element (REE, Y, Sr, Th, U) concentrations in apatite are found to increase with the mole fraction of chlorapatite (ClAp). The preference for ClAp is stronger for cations with higher charge (e.g., Th4+, U4+>REE3+) and larger ionic radii (e.g., LREE>HREE).Trace element partition coefficients between apatite and melt show up to 4 times variation between experiments, e.g., DLaAp-melt=77–281; DSmAp-melt=176–519; DSrAp-melt=4–12 and DTh,UAp-melt=4–19. The REE partition coefficients between apatite and melt (DREEAp-melt) display a concave pattern with the peak at Sm/Nd and a negative Eu anomaly, and are significantly higher than previously reported values for partitioning experiments conducted at lower pressures and higher temperatures. The high values of DLREEAp-melt demonstrate the importance of apatite in terms of LREE partitioning during sediment melting, while allanite/monazite still dominates the partitioning of Th. In the absence of allanite/monazite, apatite-buffered melt is characterized by a significant enrichment of Th relative to La. Because of the contrasting behavior of LREE and HFSE in melt with the addition of Cl and F, the fractionation of these elements in slab-derived sediment melts will be enhanced by the presence of halogens.

Diversity of Mesozoic tin-bearing granites in the Nanling and adjacent regions, South China: Distinctive mineralogical patterns

The Nanling and adjacent regions of South China host a series of tin deposits related to Mesozoic granites with diverse petrological characteristics. The rocks are amphibole-bearing biotite granites, or (topaz-) albite-lepidolite (zinnwaldite) granites, and geochemically correspond to mealuminous and peraluminous types, respectively. Mineralogical studies demonstrate highly distinctive and critical patterns for each type of granites. In mealuminous tin granites amphibole, biotite and perthite are the typical rock-forming mineral association; titanite and magnetite are typical accessory minerals, indicating high f O2 magmatic conditions; cassiterite, biotite and titanite are the principal Sn-bearing minerals; and pure cassiterite has low trace-element contents. However, in peraluminous tin granites zinnwaldite-lepidolite, K-feldspar and albite are typical rock-forming minerals; topaz is a common accessory phase, indicative of high peraluminity of this type of granites; cassiterite is present as a uniquely important tin mineral, typically rich in Nb and Ta. Mineralogical distinction between the two types of tin granites is largely controlled by redox state, volatile content and differentiation of magmatic melts. In oxidized metaluminous granitic melts, Sn4+ is readily concentrated in Ti-bearing rock-forming and accessory minerals. Such Sn-bearing minerals are typical of oxidized tin granites, and are enriched in granites at the late fractionation stage. In relatively reduced peraluminous granitic melts, Sn2+ is not readily incorporated into rock-forming and accessory minerals, except for cassiterite at fractionation stage of granite magma, which serves as an indicator of tin mineralization associated with this type of granites. The nature of magma and the geochemical behavior of tin in the two types of granites thus result in the formation of different types of tin deposits. Metaluminous granites host disseminated tin mineralization, and are locally related to deposits of the chlorite quartz-vein, greisen, and skarn types. Greisen, skarn, and quartz-vein tin deposits can occur related to peraluminous granites, but disseminated mineralization of cassiterite is more typical.

The Effect of a High Al Content on the Variation of the Total Oxygen Content in the Steel Melt during a Secondary Refining Process

The aim of this study is to clarify the mechanism of low total oxygen (T.O) contents in high‐Al containing steel grades. Steel samples are taken from a ladle during an LF‐RH process, and the compositions of both the steels and inclusions are determined. According to thermodynamic considerations, the low T.O contents of high Al steel grades are due to the low insoluble oxygen contents. Due to the high Al contents in a steel melt, thermodynamic driving forces of the Al2O3 modification are lower than those in ordinary Al‐killed steels. Both the low thermodynamic driving force of the Al2O3 modification and the inclusion removal from the melts contribute to the low CaO contents in inclusions in high‐Al steel melts. The contact angles of inclusions in high Al steel melts are higher than 90° due to the low CaO content in inclusions. Therefore, the removal tendency of inclusions in high Al steel melts is kept high throughout an LF‐RH process. Due to this high removal tendency, the T.O contents in high Al steel melts decreases remarkably during an LF refining process. Thereafter, they decrease further during the following RH treatment.

Erratum: Stability and Solubility of Pollucite In the Granite System At 200 MPa H2O

The chemistry and stability of pollucite (Pol, CsAlSi 2 O 6 )-leucite (Lct, KAlSi 2 O 6 )-analcime (Anl, NaAlSi 2 O 6 H 2 O) solid-solutions and the effects of added pollucite on phase relations in the haplogranite system were studied experimentally between 450 degrees and 850 degrees C at 200 MPa H 2 O. Addition of Cs via dissolution of pollucite lowers the haplogranite solidus by approximately 40 degrees C (to approximately 640 degrees C) and displaces the minimum melt composition slightly toward the Qtz apex. The Cs content of melt saturated in pollucite solid-solution near the minimum is approximately 5 wt.% Cs 2 O. There is substantial miscibility among Pol and Lct components at magmatic temperatures, but the Lct content of pollucite decreases linearly with decreasing temperature to zero Lct component at approximately 385 degrees C. The Lct and Anl components vary inversely in pollucite solid-solutions as a function of temperature, such that the Anl and maximum Pol components of the pollucite solid-solution increase with decreasing temperature. Natural and synthetic pollucite equilibrates readily with melt or with hydrothermal solutions (and coexisting alkali feldspars) down to temperatures below approximately 400 degrees C. The experiments do not unequivocally resolve a standing question of a miscibility gap in the Pol-Anl system at low temperature. The compositions of synthetic pollucite diverge by >15 mol.% in terms of Pol and Anl components at 450 degrees C, but as in nature, the bulk of the synthetic pollucite is intermediate in composition between the extremes.

Experimental determination of liquidus H2O contents of haplogranite at deep-crustal conditions

The liquidus water content of a haplogranite melt at high pressure (P) and temperature (T) is important, because it is a key parameter for constraining the volume of granite that could be produced by melting of the deep crust. Previous estimates based on melting experiments at low P (≤0.5 GPa) show substantial scatter when extrapolated to deep crustal P and T (700–1000 °C, 0.6–1.5 GPa). To improve the high-P constraints on H2O concentration at the granite liquidus, we performed experiments in a piston–cylinder apparatus at 1.0 GPa using a range of haplogranite compositions in the albite (Ab: NaAlSi3O8)—orthoclase (Or: KAlSi3O8)—quartz (Qz: SiO2)—H2O system. We used equal weight fractions of the feldspar components and varied the Qz between 20 and 30 wt%. In each experiment, synthetic granitic composition glass + H2O was homogenized well above the liquidus T, and T was lowered by increments until quartz and alkali feldspar crystalized from the liquid. To establish reversed equilibrium, we crystallized the homogenized melt at the lower T and then raised T until we found that the crystalline phases were completely resorbed into the liquid. The reversed liquidus minimum temperatures at 3.0, 4.1, 5.8, 8.0, and 12.0 wt% H2O are 935–985, 875–900, 775–800, 725–775, and 650–675 °C, respectively. Quenched charges were analyzed by petrographic microscope, scanning electron microscope (SEM), X-ray diffraction (XRD), and electron microprobe analysis (EMPA). The equation for the reversed haplogranite liquidus minimum curve for Ab36.25Or36.25Qz27.5 (wt% basis) at 1.0 GPa is $$T = - 0.0995 w_{{{\text{H}}_{ 2} {\text{O}}}}^{ 3} + 5.0242w_{{{\text{H}}_{ 2} {\text{O}}}}^{ 2} - 88.183 w_{{{\text{H}}_{ 2} {\text{O}}}} + 1171.0$$ for $$0 \le w_{{{\text{H}}_{ 2} {\text{O}}}} \le 17$$ wt% and $$T$$ is in °C. We present a revised $$P - T$$ diagram of liquidus minimum H2O isopleths which integrates data from previous determinations of vapor-saturated melting and the lower pressure vapor-undersaturated melting studies conducted by other workers on the haplogranite system. For lower H2O (<5.8 wt%) and higher temperature, our results plot on the high end of the extrapolated water contents at liquidus minima when compared to the previous estimates. As a consequence, amounts of metaluminous granites that can be produced from lower crustal biotite–amphibole gneisses by dehydration melting are more restricted than previously thought.