High Fe2O3 Content Research Articles

A novel measurement method for ash deposition based on coplanar capacitance principle: Theoretical, numerical and experimental studies

Monitoring for the fouling and slagging is critical to ensure the stable operation of gasification system. This paper proposes a novel measurement method for the ash deposition based on coplanar capacitance principle. A theoretical analysis of electrostatic field is conducted to obtain the correlation between the coplanar capacitance value and the deposition thickness. A finite element simulation is carried out to discuss the electric field characteristics of ash depositing on the coplanar capacitor. It shows that the capacitance value initially increases and tends to be constant with the increase of deposition thickness. The lower distance between positive and negative electrodes is favorable to the capacitance value (signal strength) but unfavorable to the maximum measurable thickness. Furthermore, a cold state experiment is conducted to verify the correctnesses of the theoretical and numerical models, and a hot state experiment is carried out to study the capacitance characteristics of sensor in the high temperature range of 700 °C–1200 °C. Results show that the permittivity of the material is lower under the higher test frequency, which leads to the lower capacitance value of sensor. The complex impedance curve of ash is conformed to IBLC dielectric model, this explains that the sensor capacitance increases with the test temperature increasing caused by the increase of permittivity due to the enlargement of ash grain. The change of Si/Al content has little effect on the dielectric properties of ash, however, the higher Fe2O3 content or the lower CaO content results into the lower ash fusion point, larger grain size, and thence higher permittivity and sensor capacitance. The maximum measurable thicknesses of the sensors in the cold state and hot state are 11.2 mm and 10.0 mm, respectively, which are independent with the test frequency, test temperature, and ash component.

Growth of kyanite and Fe‐Mg chloritoid in Fe2O3‐rich high‐pressure–low‐temperature metapelites and metapsammites: A case study from the Massa Unit (Alpi Apuane, Italy)

AbstractChloritoid and kyanite coexist in metapelites from the high‐pressure/low‐temperature Massa Unit in the Alpi Apuane metamorphic complex (Northern Apennines, Italy). The composition of chloritoid is extremely variable throughout the Massa Unit. Fe‐chloritoid occurs in association with hematite‐free, graphite‐bearing schists, whereas strongly zoned Fe‐Mg chloritoid is found with hematite and kyanite. We investigated the effect of different bulk Fe2O3 contents in controlling chloritoid composition through phase equilibria modelling of four selected samples, representative of the different chloritoid‐bearing parageneses found in the Massa Unit. The ferric iron content, measured through wet chemical titration, ranges from 0 (graphite‐chloritoid schist) to 73% of the total iron (hematite‐chloritoid schist). We show that Mg‐rich chloritoid compositions and stability of kyanite at greenschist to blueschist facies conditions can be reproduced in the MnO–Na2O–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–O (MnNKFMASHTO) chemical system only considering the presence of significant amounts of ferric iron as part of the bulk composition. The stabilization of kyanite at lower grade is directly linked to the presence of Fe2O3, which renders the reactive bulk rock composition effectively enriched in Al2O3 with respect to Fe and Mg. We also document that high Fe2O3 contents exacerbate the effect of chloritoid fractionation, producing strongly zoned Fe‐Mg‐chloritoid grains. Finally, the P–T modelling of the Massa Units performed in this study allows, for the first time, the recognition of a two‐stage evolution at peak conditions, with an earlier pressure peak (1.2–1.3 GPa at 350–400°C), and a later thermal peak (0.7–1.1 GPa at 440–480°C), compatible with subduction, underthrusting and exhumation of the Adria continental margin during growth of the Northern Apennine orogenic wedge.

Dissolution behavior of spent MgO–C refractory in the CaO–SiO2–FeO slag system as a steelmaking flux

A large amount of spent MgO–C refractory is generated in steel plant every year. Because of the similarities in chemical and mineralogical composition of slag formers and MgO–C refractory, it is possible to reuse the spent MgO–C refractory as a steelmaking flux. To achieve this goal, it should promote the dissolution of MgO–C refractory during slag forming. In this study, the effect of slag composition on the dissolution behavior of spent MgO–C refractory in the CaO–SiO2–FeO slag system and the dissolution kinetics were investigated. It showed that the dissolution rate of MgO–C refractory was controlled by surface chemical reaction. The dissolution of MgO–C refractory led to an increase in the MgO content in slag while the FeO content decreased because the graphite in refractory was oxidized by FeO. Increasing temperature significantly promoted the dissolution of MgO–C refractory. The MgO–C refractory was readily dissolved in the low-basicity slag. A higher FeO content in slag was beneficial for the oxidation of graphite in refractory, resulting in better dissolution. The dissolution thickness of MgO–C refractory could exceed 4.0 mm under these conditions and its dissolution supplied some MgO to slag.

Solubility and Activity of Iron Oxide in Solid Solutions between Ca<sub>2</sub>SiO<sub>4</sub> and Ca<sub>3</sub>P<sub>2</sub>O<sub>8</sub> at 1573 K

Towards better understanding of fundamental dephosphorization slags of the FeO-CaO-SiO2-P2O5 quaternary system, this study aimed at clarifying the thermochemical properties of iron oxide in Ca2SiO4-Ca3P2O8 solid solutions. The solubility and activity of FeO in the solid solutions coexisting with CaSiO3 at 1573 K were determined by SEM-EDX analysis and a gas equilibrium method, respectively. Based on the present experimental results, the phase relationships could be explained that the solid solution of high FeO solubility coexists with CaSiO3 and liquid slag of low FeO content, while the solid solution of low FeO solubility coexists with CaO and liquid slag of high FeO content.

Petrogenesis of the Alubaogeshan granite in the Maodeng Mo-Bi-Sn-Cu deposit, southern Great Xing’an Range, NE China: Constraints from apatite, plagioclase, magnetite and ilmenite geochemistry

The Maodeng deposit, located in Xilinhot, Inner Mongolia, is a typical Mo-Bi-Sn-Cu deposit in the southern segment of the Great Xing’an Range. It is genetically related to the Alubaogeshan granitic complex, which is composed of porphyritic monzogranite (G1), granite porphyry (G2), and alkali feldspar granite (G3). However, the comparison of physical–chemical condition and magmatic evolution of different lithofacies has not been conducted. We present in-situ major-trace elements and Sm-Nd isotopes of apatite, in-situ major-trace elements of plagioclase, as well as in-situ major elements of magnetite and ilmenite from the G1 and G2, with the goal of discussing magma genesis and its constraints on mineralization. The apatites from the two granites are characterized by relative enrichment in F and light rare earth elements (LREEs) but depletion in Cl, S, and heavy rare earth elements (HREEs), as well as obviously negative Eu, Sr, Nb, Ba, Zr, and Hf and positive Y anomalies, indicating that the two granites have similar sources and experienced significant crystallization differentiation. When compared to G1, apatites from G2 exhibit more significant Eu, Sr, and Y anomalies, as well as lower (La/Sm)N and (La/Yb)N ratios, likely due to intensive crystallization of plagioclase and exsolution of Cl-bearing magmatic fluids. The presence of core-rim zoning patterns with BSE-bright and BSE-grey domains in some G2 apatite crystals indicates extensive hydrothermal alteration. The plagioclases within G1 belong to andesine–oligoclase series corresponding to magmatic water contents of 1.4 to 1.9 wt%, and those in G2 belong to oligoclase–albite series with calculated magmatic water contents of 2.1 to 2.2 wt%. The plagioclase crystals from G1 are characterized by prominently positive Eu and moderately positive Sr and Ba anomalies, with crystals from G2 showing strongly negative Eu, Ba and Sr anomalies, indicating more significant fractionating plagioclase and apatite in G2 than G1. The magnetite compositions are distinguished by high FeO, TiO2, and MnO contents. Ilmenite usually cuts and dissolves magnetite, and contains a lot of FeO, TiO2, MnO, and Nb2O3. The magnetite and ilmenite from the two granites have a coherent negative correlation between Ti and Fe3+ but a consistent positive correlation between Ti and Fe2+, implying that they crystallized from a homologous silicate magma. During the crystallization of apatites, magmatic oxygen fugacities of the two granites were slightly above the ΔNNO buffer line. However, these were near the FMQ buffer line when the magnetite and ilmenite were in equilibrium at temperatures ranging from 561 to 666 °C, indicating a decreasing trend in oxygen fugacity during magma evolution. The apatites of both G1 and G2 have high εNd(t) values (+0.59 to + 1.94 and − 2.13 to + 0.42, respectively), and young two-stage Nd model ages (tDM2 = 775–884 Ma and 897–1106 Ma, respectively), suggesting the predominant origin of these rocks by the partial melting of a juvenile mafic lower crust and “old” pre-existing crustal components, having a substantial proportion of continental crust for G2. The decline in oxygen fugacity, enrichment of F element, highly crystallization differentiation, intense melt/fluid interaction, and the strong hydrothermal alteration for the ore-related granite could contribute to the formation of the Maodeng deposit.

HIsarna Process Simulation Model: Using FactSage with Macro Facility

The HIsarna process is one of the emerging technologies for reducing the carbon footprint of the ironmaking process, which is currently in the pilot plant stage. A kinetic HIsarna process simulation model based on the effective equilibrium reaction zone concept has been developed using the FactSage macro programming facility to advance understanding of the whole process. In the model, the HIsarna process is conceptually divided into various equilibrium zones involving combustion, coal pyrolysis and gasification, gas/slag/carbon reactions, and slag/metal reaction. The model has been validated through the pilot plant data, and the results are in good agreement with the quantity and composition of hot metal, slag, and gas. The HIsarna off-gas stream with high CO2 content can potentially allow capture and storage directly for carbon mitigation. The utilization of titanium magnetite ore in the HIsarna process has also been investigated via the developed model. The injection of titanium magnetite ore which has high FeO content decreases coal consumption. Still, it increases the slag volume as higher gangue content when keeping the same productivity as the pilot plant trial. The HIsarna process shows promising potential in using low-quality high titania iron ore as feed materials, but the slag system needs to be further optimized. From the heat distribution, the off-gas sensible heat accounts for a large part of the input heat due to its high temperature but can be recovered with good efficiency. The present model is an efficient tool for understanding the HIsarna process and providing theoretical guidance for future pilot research.

Sulphide capacity of CaO-SiO2-Al2O3-MgO-TiO2-FetO slag with high titanium and high FeO content based on HIsmelt process

ABSTRACT The sulphide capacities of CaO-SiO2-Al2O3-MgO-TiO2-FetO slags with high titanium and FetO were measured by gas-slag equilibration technique to reveal the effect of slag composition and temperature on the sulphide capacities of slags. The results showed that sulphide capacities enhanced with the increase of temperature, basicity, FetO, and MgO contents, TiO2 content increased first and then decreased in the range of 10 wt-% to 20 wt-%; the influence became negligible as the TiO2 content exceeded 25 wt-%. MgO significantly increased the sulphide capacities of slag in the range of 6 wt-% to 8 wt-%, continued to increase the MgO content, and the increasing trend of Log CS became slowly; FetO content increased from 3 wt-% to 9 wt-%, sulphide capacities increased slowly, increased dramatically in the range of 9 wt-% to 15 wt-%. Meanwhile, comparing the optical basicity models found Zhang and Tsao’s models are close to the experimentally determined values.

Middle Jurassic ooidal ironstones (southern Tibet): Formation processes and implications for the paleoceanography of eastern Neo-Tethys

The major facies changes documented in shallow-marine sediments of the northern Indian passive margin of Neo-Tethys throughout the Jurassic, from widespread platform carbonates in the Early Jurassic to organic-rich black shales in the Late Jurassic, imply a substantial turnover in oceanic conditions. All along the Tethys (Tibetan) Himalaya, from the Zanskar Range to southern Tibet, a peculiar interval characterized by ooidal ironstones of Dingjie Formation (Ferruginous Oolite Formation, FOF) marks the base of the organic-rich Spiti Shale. This laterally-extensive ooidal ironstone interval is a fundamental testimony of the mechanisms that led to major paleoceanographic changes that occurred in the eastern Neo-Tethys during the Middle Jurassic. In this article, we illustrate in detail the petrology, mineralogy, and geochemistry of ooidal ironstones and the major element contents of the entire Lanongla section. The FOF is characterized by significantly high contents of Fe2O3 (56.80% ± 9.07%, n = 7) and P2O5 (1.72% ± 1.19%, n = 7). In contrast, the Fe2O3 and P2O5 contents average 3.58% and 0.15% in the overlain carbonates of Lanongla Fm., and 5.55% and 0.16% in the overlying Spiti Shale. The ooidal ironstones are mainly composed of iron ooids with a few quartz grains and bioclasts cemented by sparry calcite. The iron ooids consist of concentric dark layers of francolite (carbonate fluorapatite), hence enriched in Ca, P, and F, and bright layers of chamosite, enriched in Fe, Si, Al, and Mg. Precipitation of francolite ensued from oversaturation of phosphorous ascribed to intensified upwelling, high biogenous productivity, and degradation of organic matter, whereas the formation of chamosite reflects enhanced continental weathering and erosion leading to increased Fe input to the ocean during transgressive stages characterized by low sedimentation rate and scarce oxygenation at the seafloor. Modern upwelling zones in outer shelf or slope areas perform similar geochemical characteristics to those as observed in this study. Under the Mesozoic greenhouse background, fluctuating redox conditions induced the alternate growth of francolite under anoxic conditions and of chamosite under suboxic conditions. Ooids were thus formed on the seafloor during continued resuspension and vertical oscillations of the chemocline rather than from interstitial waters after burial. The mineralogy of iron ooids indicates mainly reducing conditions in the water column, suggesting that extensive upwelling along the continental margin of eastern Neo-Tethys contributed significantly to the transition from carbonate deposits to organic-rich black shales during the Jurassic, as testified by the transition from well-oxygenated in Lanongla Fm. To a reduceing condition in Spiti Shale indicated by the Mn/Al ratios compared to PAAS.

On the Utilization of Modified Red Mud in Dimethyl Disulfide and Methyl Mercaptan Emission Abatement

In this paper, a novel application of industrial waste, namely red mud (RM), in the abatement of two malodorous and harmful sulfur compounds, dimethyl disulfide (DMDS) and methyl mercaptan (MM), is presented. The effects of calcination and activations with hydrochloric acid or a mixture of hydrochloric and orthophosphoric acid on the properties and performance of RM are compared using laboratory-scale experiments. The RM-based materials were characterized by XRF, XRD, FE-SEM, N2-physisorption, TGA/DTA, and FTIR analyses. RM exhibits very promising catalytic properties in the abatement of both DMDS and MM. The hydrochloric acid-activated RM was the most active in both cases, which was explained by its rather high specific surface area (144 m2 g−1), higher contents of Fe2O3 and TiO2, as well as lower content of phosphorus. For both DMDS and MM, the main oxidation products were sulfur dioxide, carbon monoxide, and carbon dioxide. DMDS was observed as a reaction intermediate in MM oxidation. While the final conversions of DMDS and MM were high, the oxidation was not complete, indicated by the formation of carbon monoxide. Nevertheless, the modified RM appears as a very interesting alternative to the existing DMDS and MM abatement catalysts.

Some Mineralogical Characteristics of the Egyptian Black Sand Beach Ilmenite Part IΙ: Rutile-Ilmenite and the Various Titanhematite Grains

In addition to the grains of homogeneous ilmenite, ferriilmenite, hematite-ilmenite exsolved intergrowths, and the partially altered ilmenite grains, other textures are detected in the separated ilmenite concentrate. The grains of rutile-ilmenite exsolved intergrowth represent 0.8% of the detected ilmenite grains. The ilmenite component of this intergrowth is detected to be ferriilmenite associated with geikielite, pyrophanite, and rutile, with Cr2O3 content ranging between 0 and 0.5%. The exsolved rutile is ferriforrous rutile composed of rutile, hematite, geikielite, and pyrophanite, its Cr2O3 content ranging between 0 and 0.4%. The detected individual titanhematite grains represent 4.4% and include 3 textures arranged, in a decreasing order of abundance, as: ilmenite-hematite, rutile-hematite, and rutile-ilmenite-hematite exsolution intergrowths. MgO and MnO have minimum values and they do not follow Fe2O3. In some homogeneous titanhematite or exsolved rutile-hematite, Fe2O3 content may be replaced with SiO2. In all titanhematite intergrown textures, the Cr2O3 content ranges between 0 and 0.1%. Only in the case of the titanhematite host with exsolved rutile, the contained MgO ranges between 1.2 and 5.3%. Some ferromagnetic titanhematite grains separated with the fraction of magnetite are detected. In these grains, the Cr2O3, MgO, and MnO contents range between 0-0.2, 0-3, and 0-1.4% respectively. Several varieties of chromite and chromspinel mineral grains are found and represent 1.1% of the detected bulk ilmenite grains. In these grains, the Cr2O3, MgO, V2O3, and Al2O3 contents range between 16.69-56.72%, 0.54-17.33%, 0.14-0.58%, and 1.33-38.79% respectively. Although they are rarely met in the ilmenite concentrate, the relatively finer grain sizes could lead to the separation of some with ilmenite fraction rather than with the ferromagnetic one. It is concluded that the problem of high Cr2O3 and Fe2O3 contents of the Egyptian beach ilmenite concentrate is not only a mineralogical problem, but also an ore-dressing one.

A baseline survey of the geochemical characteristics of the Arctic soils of Alexandra Land within the Franz Josef Land archipelago (Russia)

The compositions of soils and their parent materials were studied within one of the most northern land areas of the world — the island of Alexandra Land of the Franz Josef Land archipelago. Contents of 65 trace and major elements were determined using atomic emission spectrometry (ICP-AES) and inductively coupled plasma spectrometry (ICP-MS). Other analyzed characteristics included soil pH, particle-size distribution and contents of carbon and nitrogen. The bedrock had an alkaline pH, whereas the soil pH ranged from weakly acid to alkaline. The textural class of the soils predominantly corresponded to sandy loam. The contents of clay and silt increased with depth due to the migration of these fractions with groundwater. The studied soils were formed on basalts with high contents of MgO, Fe2O3, TiO2, Cu, Co, V, Ni, Cr, Zn, and low contents of Pb and Hg. The present study confirms that the FJL basalts are similar to the Siberian Platform basalts in composition and belong to the continental basalt series. The composition of soils was generally similar to that of the bedrock. Compared to other Arctic archipelagos (i.e., Svalbard, Severnaya Zemlya), the soils of Alexandra Land are characterized by increased contents of Cu, Mn, Co, and Fe and reduced contents of Hg, Pb, and Cd. The median concentrations (mg kg−1) of trace elements in the soils were as follows: Cu—142, Zn—100, Ni—72, Pb—2.4, Cd—0.1, and Hg—0.0052. The low contents of Hg, Pb, and Cd in the soils are indicative of low inputs of these elements from both long-range transport and local sources of pollutants.

A spectral approach on mineralogy and geochemistry of garnet skarns in Arc-Type granitoids

Garnets that common constituent of skarn type iron deposits are wide ranges of chemical compositions, and they are also important as a semi-gemstone mineral. This study has been investigated garnets and inclusions of its formed in contacts of Pertek granitoid and Keban marble by using a combination of multiple techniques including Raman spectrum, electron microprobe, petrography and LA-ICP-MS. The main mineral assemblage observed in the skarn formation is diopside, garnet, quartz, magnetite, calcite and pyrite. The garnets are in size between 1 and 7 cm and have reddish, greenish and light–dark brown colour. The compositions of the garnets are mainly grossular-andradite, andradite-grossular, less grossular and andradite. Increased porosity and horizontal flow of hydrothermal fluids during metasomatism resulted in the formation of garnets of different sizes. Raman spectroscopy studies on garnets show to be that the idiomorphic and semi-idiomorphic garnets are predominantly grosular, andradite and uvarovite in the core. Raman spectroscopy studies on garnets showed to have predominantly grossular, andradite and uvarovite composition in the core of the idiomorphic and semi-idiomorphic garnets. As for the rare earth element (REE) analysis and distribution model, the chondrite-normalized REE patterns of all garnets in the study area have similar trends and generally in the right-slopping shape depleted in HREE and enriched in LREE, mostly controlled by adsorption. High Fe2O3, CaO and MgO contents may cause to high mobility during skarn formation associated with contact metamorphism and cation exchange via hydrothermal fluids (eg uvarovite in the core). All garnets have generally positive Ce and positive Eu anomalies. These results suggest that the garnets in the studya area formed in conditions showing increase in pH and high oxygen fugacity or decrease in temperature in the source of the hydrothermal fluids.

A Novel Process Design and Industrial Practice of Single‐Slag Smelting in 120 t Converter

With the reduction of raw material quality and the improvement of user requirements, the cost of dephosphorization increases. Steel plants urgently need an efficient and economic dephosphorization process to support the production. To address this issue, first, the migration and distribution of phosphorus in the converter smelting process are described quantitatively. Based on the regular solution model, the influence of slag components and temperature on the dephosphorization capacity of steel slag is explored. Afterward, considering the phosphorus distribution ratio, melting point, and phosphorus capacity of slag, the advantages of the slag‐forming route with higher FeO content in rapid slag formation and dephosphorization are expounded. Based on the guidance of the slag‐forming route, the scheme of controlling oxygen lance position and charging is optimized, and a novel blowing control mode is proposed. Finally, industrial tests on a 120 t converter show that the optimized smelting mode significantly reduces the cost and improves the efficiency. As a result, the lime consumption used to smelt a ton of steel is reduced by 3.67 kg t−1, and the dephosphorization rate is still increased by about 3.07%.

Preparation of a highly color-saturated amorphous photonic crystal structural color glaze by imitating the multilayered structure of Jun porcelain

As is well known, a black background can remove the influence of background light reflection and improve the color saturation of amorphous photonic crystal structural color. Coincidentally, a multilayered structure with a black layer of glaze base was found in Jun porcelain. Based on this, black crucible soil with high Fe2O3 content was used as the raw material for imitating the multilayered structure. Furthermore, the reason for the formation of the black layer and its influence law on the saturation of structural color glazes were also studied. The results indicated that the diffusion of iron and titanium ions under the concentration gradient promoted the formation of a black layer. In addition, with increasing amounts of black crucible soil, the diffusion amount and depth of the transition metal ions were large, and the black layer was thickened. It was conducive to improving color saturation for the structural color glaze.

ALMUS (TOKAT) YÖRESİNDEKİ AKİKLERİN JEOKİMYASAL ÖZELLİKLERİNİN DEĞERLENDİRİLMESİ

The Upper Cretaceous Artova ophiolite complex, represented by metabasic and ultrabasic rocks, overlies the Paleozoic aged Tokat metamorphites, which form the basis of the study area, by the tectonic boundary. Haydaroğlu formation, which includes Middle Eocene aged volcanogenic units, cuts and covers the older units. Agates (agates) in the Almus region are found in the form of nodules in the volcanogenic sandstones of the Haydaroğlu formation along an approximately E-W trending fault. The Lower Miocene aged Almus formation, which consists of sedimentary rocks such as sandstone, conglomerate and marine limestone, also unconformably overlies all units.
 Almus region agates contain on average 93.4% SiO2, 3.59% Fe2O3, 0.03% MgO, 0.72% CaO, 793 ppm Cr2O3, 12 ppm Ni, 13.4 ppm Cu, 4.7 ppm Pb, 35.4 ppm Zn. The high Cr and Ni in agates are associated with the Artova ophiolite complex in the region. Cu, Pb and Zn are associated with the early stages of volcanism. The high Fe2O3 content in agates is associated with hematite and goethite, and they were transported into agates before SiO2 emplacement. The CaO in the agate is the product of the last phase of the solution forming the agate, and MgO is associated with the presence of dolomite. 
 Evaluation of the results of geochemical analysis shows that SiO2, which is the main component due to the hydrothermal activities that occurred after the rock formation of the Haydaroğlu formation, unlike the volcanic bedrocks of the agates according to the main oxides, trace and rare earth elements, was emplaced epigenetically as a result of the circulations in the volcanogenic sandstones.

MINERALOGIA E ASPECTOS GEOQUÍMICOS DOS LATERITOS FOSFÁTICOS DA ILHA PEDRA GRANDE DO GURUPI (PA)

The Pedra Grande Island located at the mouth of the Gurupi River, is equivalent to a small plateau, which is currently partially drowned by the sea, where the impacts of the waves have already left longitudinal fractures and caves on the island. The island is entirely made up of lateritic rock, represented by the ferruginous lateritic crust, exhibiting a dominantly brownish red coloration. Texturally it consists of nodules, pisoliths and pseudo-fragments, which are surrounded by a whitish cream cement, giving the rock a general brechoid appearance, in addition to columnar and cavernous features. Two mineralogical associations are individualized in these laterites: a group formed by iron and calcium phosphates, widely developed in the ferruginous lateritic crust, together with iron oxy-hydroxides; and another formed by the aluminous phosphates, which constitute the whitish cream phosphate cement. The quantification of major, minor and trace elements revealed high contents of Fe2O3, P205 and A1203, and low of SiO2. In terms of traces, Mn and Zn display low contents, associated with ferruginous lateritic crust. On the other hand, rare earth elements are more concentrated in phosphate cement, mainly in Ce, Nd and La. The Ilha de Pedra Grande do Gurupi exhibits some mineralogical and chemical similarities with other occurrences of lateritic phosphates in the region, located on the continent. This correlation reveals that in the recent geological past, the ocean coastline presented a very different morphology from the current one. The geochemical and mineralogical analyzes of the Pedra Grande laterites allow us to suppose that this lateritic profile developed under a tropical climate and semi-flat topography, enriching itself in phosphorus from a phosfor-bearing parent rock, which could have the following characteristics: a clayey rock, with of shales, carbonates and phosphorites, or even a low-grade metamorphic rock, composed of schists and phyllonites containing phosphorite levels. Keywords: ferruginous crust; breccia like rocks; duphrenite; mitridatite; crandallite.

Mineralogical and geochemical studies of copper mineralization in the Paleozoic sedimentary section in southwestern Sinai, Egypt

The present study provides new insights into the distribution and characteristics of copper-bearing Paleozoic clastic-carbonate units, Araba and Um Bogma formations in southwestern Sinai, Egypt. Malachite, azurite, atacamite, chrysocolla, and cuprite occur as disseminations or stratiform, layer-parallel streaks, and lenticular bodies that are intercalated with vanadiferous sandstones in the middle unit of the Araba Formation. The vanadiferous sandstones are rich in mottramite, mimetite, duftite, beudantite, descloizite and vanadinite. The Um Bogma Formation is characterized by uncommon chalcanthite, antlerite, malachite, chrysocolla, covellite, and chalcocite in addition to traces of pyrite and barite. These ore minerals occur as acicular, fibrous, fracture-filling, disseminated, and pore-filling patches and are associated with Mn-minerals. Copper minerals form also thin laminae in the manganiferous and black organic-rich shales of the Um Bogma Formation.Copper and vanadium minerals are disseminated in the arkose, subarkose, sublitharenite, graywacke, shale, siltstone and dolostone members of the host formations. Elevated copper concentrations (up to 5.04 wt%) and vanadium (≤362.3 ppm) are associated with high CaO and MgO contents in the intergranular patches and discontinuous laminae. In the Um Bogma Formation, the mineralized layers show high contents of MnO (up to 84.27 wt%) and Fe2O3 (up to 72.1 wt%), Ba (0.03–2.86 wt%), S (up to 0.452 wt%) and Ni (0.012–0.041 wt%).Mineralogical and textural characteristics of the studied rocks indicate that copper and vanadium minerals in the Araba Formation are related to supergene processes and telodiagenesis after oxidation of sulfides and dissolution of feldspar grains and carbonate cement in the clastic rocks most probably during the Upper Devonian-Lower Carboniferous Hercynian event. In the Um Bogma Formation, copper mineralization is a supergene alteration of hydrothermal Fe-Mn minerals and associated primary Cu-Zn sulfides. Hydrothermal fluids likely mobilized several metals, i.e., Fe, Mn, and Cu, within dissolved and karstified carbonates in the Um Bogma Formation.

Role of magma differentiation depth in controlling the Au grade of giant porphyry deposits

Porphyry deposits are the world's most important source of Cu and a major source of Au. It has been recognized that low Au grades generally characterize porphyry deposits in thick continental arcs, like the Andes, where the magmas are likely to differentiate at depth. In contrast, Au-rich porphyries are mainly found in thin island arcs, for example, those of the southwest Pacific, or associated with short extensional periods in continental arcs, where the magmas are likely to experience relatively shallow differentiation. However, the key factors that control this difference remain debated. This study shows that the Au grade of giant porphyry deposits and La/Yb ratios of the ore-associated suites are negatively correlated (r=∼0.7, p=10−7). We attribute the negative correlation to be mainly due to varying sulfide saturation histories, modulated by the depth of magma differentiation.Magmas differentiating in deep crustal reservoirs are likely to reach sulfide saturation early due to high pressure and early depletion of FeO (calc-alkaline trend). Early sulfide saturation causes most Au to be held in cumulus sulfides, making it unavailable to enter ore-forming fluid released in the upper crust, resulting in Au-poor porphyry systems. In contrast, magmas evolving in shallow reservoirs are likely to experience late sulfide saturation because of the high sulfur solubility induced by low pressure and the high FeO content of the melts (tholeiitic trend). Late sulfide saturation enhances the potential of a magmatic system to form Au-rich porphyry deposits due to the high Au content of the magma at voluminous fluid saturation and efficient Au transfer from melt to the ore-forming fluids via sulfide-fluid interaction. The link between average magma differentiation depth and Au content is supported by platinum-group element geochemistry of the porphyry ore-forming suites, which shows that the magmas differentiating at shallower depths (lower La/Yb) reach sulfide saturation later and therefore have higher Au concentrations than those that differentiate at deeper levels (higher La/Yb). Numerical models for ore-associated magmas with different sulfide saturation histories indicate that variations in the Au grades of giant porphyry deposits can be explained by the variations in the timing of sulfide saturation. Based on the results, we propose that Au concentration in the magma, modulated by average magma differentiation depth and sulfide saturation history, is one of the critical factors controlling the Au grade of giant porphyry Cu deposits.

Melting–Dropping Property of Blast Furnace Charge on the Basis of Its Slag Formation Behavior

In order to reveal the melting–dropping property of a charged blast furnace (BF) and the mechanism of its slag formation, such as the temperature interval of slag formation, the pressure drop during the reduction process, and the K value of each sample, the soft melt drop experiment was tested in a large-capacity melting–dropping furnace. The results show that a positive linear relationship exists between the slag melting behavior and the melting–dropping property of the corresponding charge. The results indicate that owing to their poor melting–dropping property, single iron ores are not suitable for BF production and the charging mix can improve slag formation as well as the melting–dropping property when the temperature is increased. Chemical composition is the key factor that will affect slag formation. An excessive amount of lump ore in the charging mix favors the formation of a high-fusion point slag phase such as spinel at low temperatures. The charging mix containing fewer lump ore has high FeO content in the slag, decreasing fluidity at increased temperature. Consequently, the gas path is choked and permeability is reduced.

Preparation of refractory materials from electric furnace ferronickel slag and blast furnace ferronickel slag: A comparison

The feasibility of converting high-iron electric furnace ferronickel slag (EFFS) and high-calcium blast furnace ferronickel slag (BFFS) to refractory materials was assessed by sintering with the addition of low-cost sintered magnesia. The preparation and properties of the refractory materials were investigated and compared based on both thermodynamic and experimental analyses. It was shown that the addition of sintered magnesia could restrain the negative effects of high contents of FeO and CaO in EFFS and BFFS, respectively, with low mass ratios of magnesia to silica (m(MgO)/m(SiO2)) by suppressing the formations of the phases with low melting points, including enstatite, liquid phase, monticellite, and merwinite. Compared to that prepared from BFFS, the refractory material derived from EFFS with higher refractoriness (1663 ºC vs. 1700 ºC), lower bulk density (2.92 g/cm3 vs. 2.70 g/cm3), and larger compressive strength (110.2 MPa vs. 158.5 MPa) was obtained by sintering at 1350 ºC for 3 h with a smaller addition of sintered magnesia (45 wt% vs. 30 wt%). This study proved the possibility of turning different types of ferronickel slag into refractory materials, realizing overall and value-added utilization of the waste.