Flotation study on high-hercynite ilmenite ores

Ilmenite from Polish magnetite-ilmenite ores has been floated with tall oil. Chemical and mineralogical analysis of the flotation products established that the ores containing hercynite are difficult to upgrade. For ore A (18.7% hercynite and 32.8% ilmenite) and ore B (9% hercynite and 41.3% ilmenite) poor concentrates containing much less than the required 45% TiO₂ have been obtained. It has been found that the higher concentration of hercynite in the feed, the lower the grade of concentrates in respect to TiO₂ is obtained. Ilmenite ore containing a minor amount of hercynite (ore C, 0.15% hercynite and 12.3 ilmenite) gives a good concentrate. By means of microscopic observation it was established that hercynite floats together with ilmenite in the rougher flotation but is partially depressed in the cleaning and scavenging flotation.     

Mineralogy, Chemical Characteristics and Upgrading of Beach Ilmenite of the Top Meter of Black Sand Deposits of the Kafr Al-Sheikh Governorate, Northern Egypt

Egyptian beach ilmenite occurs in a relatively high content in the naturally highly concentrated superficial black sand deposits at specific beach zones in the northern parts of the Nile Delta at Rosetta. Microscopic study shows that the ilmenite occurs as fresh homogeneous black or heterogeneous multicoloured altered grains and exhibits three types (homogeneous, exsolved and altered) of ilmenite varieties. XRD data of ilmenite indicates their association with minor hematite and quartz, whereas leucoxene shows its association with Nb‐rutile, pseudorutile and hematite. Grain size distribution suggests a very fine sand size of >89% and 80% and a fine sand size of 10.5% and 18.3% for fresh and altered ilmenites, respectively. The density of fresh, altered ilmenite and leucoxene concentrates varies from 2.70, 2.50 to 2.40 ton/m³, suggesting a gradual decrease from high grade fresh to leucoxene and consistent with variation in magnetic susceptibility as a consequence of the leaching of iron. Mass magnetic susceptibility reveals 97.6% of ilmenite and 92% of the altered form are obtained at 0.20 and 0.48 ampere. Fresh ilmenite exhibits variable TiO₂ (47.18%) and Fe₂O₃^T (46.10%) with minor MnO, MgO and Cr₂O₃ (1.22, 1.10 and 0.51%). The altered ilmenite is higher in TiO₂ (76.16%) and SiO₂ (4.68%) and lower in Fe₂O₃^T (14.45%), MnO, MgO and Cr₂O₃ (0.39, 0.52 and 0.11%) compared with the fresh form. Three concentrates of ilmenites (G1, G2 and G3) were prepared from crude ore using a Reading cross belt magnetic separator under different conditions, revealing a gradual increase of TiO₂, SiO₂, Al₂O₃ and CaO accompanied by a decrease of Fe₂O₃^T, MgO and Cr₂O₃ with repetition of the separation processes. Several ore dressing techniques were carried out to upgrade the ilmenite concentrate.     

Crystallization of titaniferous chromite,magnesian ilmenite and armalcolite in tholeiitic suites in the Karoo Igneous Province

Titaniferous chromite (up to 8 wt% TiO₂) and magnesian ilmenite (up to 10 wt% MgO) coexist at the base of the differentiated tholeiitic Mount Ayliff Intrusion in the Karoo Province of southern Africa, suggesting that the original magma was TiO₂-rich. Picritic lavas with 3% TiO₂ from the Lebombo monocline of the Karoo Province also contain microphenocrysts of magnesian ilmenite (up to 6 wt% mgO) and armalcolite (up to 7 wt% MgO). These oxide mineral associations and compositions are atypical of tholeiitic magmas, in which chromite usually has less than 1 wt% TiO₂, ilmenite less than 3 wt% MgO and armalcolite is rarely a primary mineral. Experiments have been conducted at one atmosphere pressure on a range of compositions to determine the effect of TiO₂ on the crystallization and composition of chromite, ilmenite and armalcolite. The results indicate that increasing the TiO₂ content of picritic magmas increases the TiO₂ content of the spinel, mainly at the expense of Al₂O₃, whereas Cr₂O₃ is not affected. Spinel compositions in the Mount Ayliff Intrusion (with over 45 wt% Cr₂O₃, less than 10 wt% Al₂O₃ and 8 wt% TiO₂) were duplicated in experiments on a picrite at temperatures of about 1,200°C at the Ni/NiO buffer. Increasing fO₂ from fayalite-magnetite-quartz to Ni/NiO buffer is shown to increase the crystallization temperature of armalcolite and to decrease that of ilmenite. The total FeO content of the liquid has little influence on the crystallization temperature of these phases. The TiO₂ content of the liquid, when either ilmenite or armalcolite crystallizes, varies inversely with SiO₂ content. The MgO content of the liquid at which ilmenite or armalcolite crystallizes depends upon the TiO₂ content of the starting composition, with naturally occurring and experimetally determined saturation being demonstrated for liquids with 5 wt% MgO and 5.5 wt% TiO₂. The partition coefficent for MgO between armalcolite or ilmenite and liquid is about 1.5. Observed magnesian armalcolite and ilmenite compositions in picrite lavas (both minerals) and in the Mount Ayliff Intrusion (ilmenite only) are consistent with crystallization from a TiO₂-rich magma with approximately 5 wt% MgO. The Fe ₂ ³⁺ TiO₅ component of armalcolite in the picrite lavas matches those formed experimentally at temperatures of 1,150–1,110°C and fO₂ of the Ni/NiO to Ni/NiO+1 log unit. Similarities also exist between the compositions of chromite, ilmenite and armalcolite and liquid fraction-ation trends of some Hawaiian high-TiO₂ lavas and the experimental studies presented here.     

Effects of mineralogical and textural characteristics of ilmenite concentrate on synthetic rutile production

The effect of mineralogy and texture of Qara-aghaj ilmenite concentrate on titanium dioxide prepared via reduction-slagging acid leaching process as a raw material in chloride route was investigated. The concentrate contains 44.5 % TiO₂ and its content in ilmenite lattice varies from 41.6–48 %. Hematite exsolved lamellae inside ilmenite which affect the reduction process positively are host of the most of the Cr and V as pigment colorizer metals. Apatite fine inclusions inside ilmenite as the source of Ca and P could have negative effects on synthetic rutile. Spinel ultrafine particles inside ilmenite containing Al and Si could also affect the synthetic rutile negatively. The other important elements which have been substituted in ilmenite lattice are Mg and Mn. The prepared titanium dioxide concentrate containing 91 % TiO₂ and 0.6 % Fe₂O₃ is mainly formed by rutile and small amount of anatase and Ti₂O₃ phases. The solid solution of rutile inside Ti₂O₃ was also observed. The content of Cr, V, Mn, and Al are decreased to permissible amount during slagging and leaching process while the quantity of other impurities such as Mg, Si, and Ca are relatively high in the product, and they cause some difficulties in pigment production via chloride route. The Mg and Ca sourced from ilmenite lattice and apatite inclusions, respectively, can affect the precipitation process. So, it is predicted that Qara-aghaj ilmenite concentrate will be suitable for sulfate route, but it is necessary to investigate comprehensively.     

Weathering of ilmenite from Chavara deposit and its comparison with Manavalakurichi placer ilmenite,southwestern India

The magnetic fractions of ilmenite from the beach placer deposit of Chavara, southwest India have been studied for mineralogical and chemical composition to assess the range of their physical and chemical variations with weathering. Chavara deposit represents a highly weathered and relatively homogenous concentration. Significant variation in composition has been documented with alteration. The most magnetic of the fractions of ilmenite, separated at 0.15 Å, and with a susceptibility of 3.2 × 10^?6 m³ kg^?1, indicates the presence of haematite–ilmenite intergrowth. An iron-poor, titanium-rich component of the ilmenite ore has been identified from among the magnetic fractions of the Chavara ilmenite albeit with an undesirably high Nb₂O₅ (0.28%), Cr₂O₃ (0.23%) and Th (149 ppm) contents. The ilmenite from Chavara is compared with that from the nearby Manavalakurichi deposit of similar geological setting and provenance. The lower ferrous iron oxide (2.32–14.22%) and higher TiO₂ (56.31–66.45%) contents highlight the advanced state of alteration of Chavara. This is also evidenced by the relatively higher Fe³⁺/Fe²⁺ ratio compared to Manavalakurichi ilmenite. In fact, the ilmenite has significantly been converted to pseudorutile/leucoxene.     

攀枝花岩体钛铁矿成分特征及其成因意义

峨眉大火成岩省是全球最大的钒钛磁铁矿床聚集区,攀枝花岩体是其中的典型代表。根据岩性特点,攀枝花岩体主体可划分为上、中、下三个岩相带,其中中部岩相带和下部岩相带岩性旋回非常发育,每个旋回从下向上铁钛氧化物和暗色硅酸盐矿物逐渐减少,块状铁钛氧化物矿石或磁铁矿辉长岩都出现在每个旋回的底部和下部。然而,尽管钛铁矿固相线以下固溶体出溶远弱于磁铁矿,从而能更好地保留成因信息,但其成分变化的成因意义没有受到足够重视。本次研究发现作为主要金属氧化物之一的钛铁矿的成分不仅在不同岩性中有明显差异,同时,中、下部岩相带的各岩性旋回中钛铁矿成分也具有周期性变化。例如,块状矿石中钛铁矿具有最高的MgO和TiO2及最低的FeO、Fe2O3和MnO,而辉长岩中钛铁矿则具有相反的成分特征。同时,钛铁矿的MgO含量与磁铁矿的MgO含量及橄榄石的Fo牌号具有显著的正相关关系。这种规律性变化说明每个旋回可以代表一次比较明显的岩浆补充,每次新岩浆补充后,钛铁矿和磁铁矿及橄榄石都是结晶较早的矿物。与Skaergaard岩体相比,攀枝花岩体钛铁矿的MgO含量较高,表明攀枝花岩体分离结晶过程中铁钛氧化物结晶较早;与挪威Tellnes斜长岩套铁钛矿床中的钛铁矿相比,攀枝花岩体的钛铁矿不仅具有较高的MgO和FeO,还具有极高的TiO2和MnO,但Fe2O3却很低,说明地幔柱背景下形成的钛铁矿与斜长岩套中钛铁矿的成分有显著的区别。     

Titanium solubility in olivine in the system TiO<Subscript>2</Subscript>–MgO–SiO<Subscript>2</Subscript>: no evidence for an ultra-deep origin of Ti-bearing olivine

The finding of ilmenite rods in olivine from orogenic peridotites has sparked a discussion about the processes of incorporation and exsolution of titanium in olivine. We have experimentally investigated the solubility of Ti in olivine as a function of composition, temperature and pressure in the synthetic TiO₂–MgO–SiO₂ system. Experiments at atmospheric pressure in the temperature range 1,200–1,500°C showed that the highest concentration of TiO₂ is obtained when olivine coexists with spinel (Mg₂TiO₄). The amount of TiO₂ in olivine in the assemblages olivine + spinel + periclase and olivine + spinel + ilmenite at 1,500°C was 1.25 wt.%. Changes in the coexisting phases and decreasing temperature result in a significant reduction of the Ti solubility. Olivine coexisting with pseudobrookite (MgTi₂O₅) and a Ti–Si-rich melt at 1,500°C displays a fourfold lower TiO₂ content than when buffered with spinel. A similar decrease in solubility is obtained by a decrease in temperature to 1,200°C. There is a negative correlation between Ti and Si and no correlation between Ti and Mg in Ti-bearing olivine. Together with the established phase relations this suggests that there is a direct substitution of Ti for Si at these temperatures, such that the substituting component has the stoichiometry Mg₂TiO₄. The unit cell volume of olivine increases systematically with increasing TiO₂ content demonstrating that the measured TiO₂ contents in olivine are not caused by micro-inclusions but by incorporation of Ti in the olivine structure. Least squares fitting of 20 olivine unit cell volumes against the Ti content yield the relation: V (ų)=290.12(1) + 23.67(85) N_Ti. The partial molar volume of end-member Mg₂TiO₄ olivine (N_Ti=1) is thus 47.24±0.13 cm³. The change of the Ti solubilty in olivine coexistent with rutile and orthopyroxene with pressure was investigated by piston cylinder experiments at 1,400°C from 15 to 55 kbar. There is no increase in TiO₂ contents with pressure and in all the experiments olivine contains ~0.2 wt.% TiO₂. Moreover, a thermodynamic analysis indicates that Ti contents of olivine coexisting with rutile and orthopyroxene should decrease rather than increase with increasing pressure. These data indicate that the ilmenite exsolution observed in some natural olivine does not signify an ultra-deep origin of peridotite massifs.     

TiO2 activity in metamorphosed pelitic and basic rocks: principles and applications to metamorphism in southeastern Canadian Cordillera

The activity of TiO₂ can be precisely defined as a function of pressure, temperature and activities of other components for common mineral assemblages in metapelites (ilmenite-quartz-garnet-plagioclase-Al₂SiO₅) and in metabasites (plagioclase-sphene-ilmenite-quartzgarnet). These mineral assemblages can be modelled by the equilibria: 1) 3ilmenite+Al₂SiO₅+2quartz=almandine+3TiO₂ 2) anorthite + 2sphene = grossular + 2TiO₂ + quartz 3) 3anorthite+3quartz+6ilmenite = grossular+ 6TiO₂+2almandine. These mineral assemblages can be used at (rutile saturation) and a given T to get maximum pressure limits of some metapelites and metabasites. When electron microprobe analyses of mineral grains adjacent to Ti-bearing phases are made, these data give maximum pressure estimates in reasonable agreement with other geobarometers. The activity of TiO₂ in many metapelites is very near rutile saturation, but for metabasites the activity of TiO₂ in some sillimanite zone rocks is as low as 0.6. The solubility of TiO₂ in biotite, hornblende and garnet is a complex function of T, P, the activities of components in coexisting minerals and crystal chemical constraints in these minerals. At a given P and T the solubility of TiO₂ in biotite and hornblende does not appear to be strongly dependent upon for sphene and ilmenite versus rutile-bearing assemblages.     

Ore petrology of the V-Ti magnetite (lodestone) layers of the Kurihundi area of Sargur schist belt,Dharwar craton

The V-Ti magnetite layers (lodestone) occur within the layered gabbro-anorthosites-ultramafic rocks emplaced into the migmatitic gneisses close to the high grade Archeaen Sargur supracrustal rocks in the Kurihundi area. The ore petrographic studies of the lodestone reveal the presence of primary Ti-magnetite, ilmenite, ulvospinel, pleonaste, hematite and pyrite, chalcopyrite, pyrrhotite and secondary Ti-maghemite, martite and goethite as well as secondary covellite. These layers contain Ti-magnetite (60%) and ilmenite (30%) with silicates (<5%) exhibiting granular mosaic texture with well-defined triple junctions and are classified as adcumulus rocks. The grain-boundary relationships in the ores indicate considerable postcumulus growth and readjustment due to combined effects of sintering and adcumulus growth. Intergrowth textures (ulvospinel, ilmenite and pleonaste in Ti-magnetite and hematite in ilmenite) reflects exsolution features crystallized from solid-solutions compositions under different conditions of oxygen fugacities. Larger bodies of pleonaste and ilmenite in Ti-magnetite become lensoid or rounded in outline and these morphological modifications took place during the regional upper amphibolite to lower granulite facies metamorphism at 2.6 Ga ago. The lodestone contains high TiO₂ (20 to 22.59 wt%), with V₂O₅ (0.85 to 1.15%) and Fe₂O₃ ^t (72.03 to 74.25%). Ti-magnetite shows alteration to Ti-maghemite, martite and goethite due to low temperature oxidation and hydration during weathering.     

Coexisting garnets and ilmenites synthesized at high pressures from pyrolite and olivine basanite and their significance for kimberlitic assemblages

Coexisting garnets and ilmenites have been synthesized at high pressure (21–40 kb) within the temperature range between 900 and 1100 °C from pyrolite-less-40% olivine and olivine basanite with various water contents. The two compositions yield phases with a range in the 100 Mg/Mg+Fe ratio for both garnet (41–76) and ilmenite (15–47). The distribution coefficient for iron and magnesiaum (K _{D(Fe, Mg)} ^ilm-ga = 4.0±0.5) for coexisting phases does not appear to vary with change in the bulk composition or temperature of synthesis. The synthesized ilmenites are of similar composition to those of kimberlites in 100 Mg/Mg+Fe ratio and Al₂O₃ and Cr₂O₃ solid solution. Cr₂O₃ content in ilmenite is dependent on Cr₂O₃ in the bulk composition and also on Fe₂O₃ content of ilmenite. Fe₂O₃ content of ilmenite is very sensitive to f _O2 and natural ilmenites from peridotites have formed under low f _O2. Al₂O₃ solid solution in ilmenite as well as TiO₂ in coexisting garnet tend to be higher with higher temperature. All the variety of compositions of ilmenites from kimberlites may be obtained from rocks rather close in composition to those used in experiments, within the same range of pressure and temperature but at variable oxygen fugacities.     

Chromiferous spinels of the elephant's head dike

Analysis by optical, X-ray diffraction and microprobe methods, of essentially unzoned, disseminated spinels within cumulus picrites and olivine gabbros reveals an unbroken range of compositions from aluminian chromite (34% Cr₂O₃) to chromian magnetite (4% Cr₂O₃). TiO₂ contents vary between 0.5 and 7.7%. Exsolution of ilmenite indicates originally higher TiO₂ contents. Quenched contact-facies rocks with abundant olivine phenocrysts contain strongly zoned spinels in which a titaniferous chromian magnetite rim (16% Cr₂O₃, 10% TiO₂) encloses cores of weakly titanian chromite (40% Cr₂O₃). Platy dendrites of exsolved spinel occur in abundance within cumulus olivines. The evidence suggests that crystallization of the disseminated spinels occurred under the influence of an increase in oxygen fugacity towards the interior of the intrusion, and that the compositional diversity has stemmed from the homogenization of originally zoned grains mantled to varying degrees by high-Ti, low-Cr rims.     

Heavy mineral distribution and characterisation of ilmenite of Kayamkulam — thothapally Barrier Island, southwest coast of India

Mineral concentration and ilmenite characterization of the Thothapally — Kayamkulam Barrier Island of the southern Kerala has been studied. 96.86% concentrations of heavy minerals are recorded in the surficial and core samples (4 m) in the southern Kayamkulam and northern Thothapally areas. The total heavy mineral content decreases with depth. The primary heavy mineral suite of the surficial and core samples consists of ilmenite, sillimanite, zircon, garnets, rutile, monazite and magnetite. Longshore current and onshore-offshore movements of sediment during the southwest monsoon are primarily responsible in sorting of the heavy minerals. TiO₂ content in ilmenite is significantly higher in the Kayamkulam core sediments than the surface samples. XRD analysis supports intensive weathering and alteration leading to the higher TiO₂ concentration. Higher percentage of ferric iron than ferrous iron in the core samples reveals that considerable weathering occurred under burial condition. SEM examination of ilmenite grains reveal the presence of solution pit, chemical leaching, corrosion and replacement textures, supporting the intense epigenetic alteration and weathering under subaerial condition and post-depositional changes by water-table condition.     

Experimental determination of activities in FeTiO3-MnTiO3 ilmenite solid solution by redox reversals

 Solid solutions of (Fe,Mn)TiO₃ were synthesized, mostly at 0.10 X_Mn intervals, at 1 bar, 900°C and log f _{O 2} = –17.50. Analysis by EMP indicate an ideal stoichiometry for the Fe-Mn ilmenites with (Fe+Mn) = Ti = 1.000 when normalized to 3 oxygens. Their unit cell volume increases linearly with X_Mn. The composition of Fe-Mn ilmenite coexisting with metallic Fe and rutile was reversed at 1 bar, 700–900°C and fixed f _{O 2} in a gas-mixing furnace. Oxygen fugacity was controlled by mixing CO₂ and H₂ gas and was continuously monitored with an yttrium-stabilized zirconia electrolyte. Solution properties of Fe-Mn ilmenite were derived from the experimental data by mathematical programming (Engi and Feenstra, in preparation) including notably the results of Fe-Mn exchange experiments between ilmenite and garnet (Feenstra and Engi, submitted) and anchoring the standard state properties to the updated thermodynamic dataset of Berman and Aranovich (1996). The thermodynamic analysis resulted in positive deviations from ideality for (Fe,Mn)TiO₃ ilmenite, which is well described by an asymmetric Margules model with W^H _FeFeMn = –9.703 and W^H _FeMnMn = –23.234 kJ/mol, W^S _FeFeMn = –19.65 and W^S _FeMnMn = –22.06 J/(K·mol). The excess free energy for Fe-Mn ilmenite derived from the redox reversals is larger than in the symmetric ilmenite model (W^G _FeMn = +2.2 kJ/mol) determined by O'Neill et al. from emf measurements on the assemblage iron-rutile-(Fe,Mn)ilmenite. Received: 10 January 1996 / Accepted: 11 July 1996     

Heavy minerals in stream sediments,Southwest Norway

As part of a regional prospecting programme, 600 panned stream sediment concentrates from 1000 km² have been examined for scheelite (CaWO₄) using ultraviolet light. The mineralogical compositions of the heavy mineral concentrates were determined and related to bedrock geology. The results of the investigation are presented on maps showing the distribution of scheelite, magnetite, and ilmenite. Follow-up work resulted in the discovery of nine new tungsten occurrences. Magnetite dominates in areas of acid rocks, and ilmenite in areas of basic rocks. The areal distribution of hornblende and hypersthene reflects the metamorphic grades.     

Production of high titania slag by Electro-Slag Crucible Melting (ESCM) process

In this research, ilmenite concentrate of Iran region successfully was smelted by Electro-Slag Crucible Melting (ESCM) process to produce TiO₂-rich slag as primary product and pig iron as by-product. Moreover, effects of reductant (carbon) amount and smelting time on TiO₂ and FeO content of slag and iron recovery were studied. It is found that addition of carbon excess to stoichiometric amount decreases the iron recovery and TiO₂ content in slag. If the smelting time keeps between 0 to 17 min, the TiO₂ content and iron recovery will be increased, whereas smelting time in excess of 17 min will cause products decline significantly. At optimum conditions, TiO₂ content in slag and the iron recovery are 70 wt.% and 84%, respectively. Kinetic studies proved that the reduction of equivalent FeO was first-order reaction. The studies made by X-ray diffraction analysis showed that formation of the titanium sub-oxides (Ti₃O₅ and Ti₂O₃) causes the decrease in iron recovery and TiO₂ content.     

Hydrogen peroxide leaching of hydrolyzed titania residue prepared from mechanically activated Panzhihua ilmenite leached by hydrochloric acid

The hydrolyzed titania residue with mainly precipitated hydrated TiO₂ is prepared from mechanically activated Panzhihua ilmenite leached by hydrochloric acid. We use H₂O₂ as a coordination agent to leach Ti from the hydrolyzed titania residue. The effects of H₂O₂ to-hydrolyzed titania residue mass ratio, leaching pH value, leaching temperature, leaching time, and H₂O₂ concentration on leaching of hydrolyzed titania residue by H₂O₂ are investigated. The recovery of Ti is above 98% under the optimal conditions. XRD shows that the peroxo-titania powder prepared by boiling the aqueous titanium peroxide solution is crystalline anatase phase. A well-crystallized anatase TiO₂ and rutile TiO₂ can be obtained through calcining at the temperature of 800 and 1000 °C, respectively. EDS shows that the impurities including silicon are enriched in the leaching slag. Little Si is detected as the only impurity in the synthetic TiO₂ due to the weak alkaline condition of leaching.     

Effect of mineralogy and texture in the TiO2 pigment production process of the Tellnes ilmenite concentrate

Summary The mineralogy and textural relationships of the Tellnes ilmenite concentrate were determined to evaluate the effect of mineralogical characteristics of the raw material on sulphate-route TiO₂ pigment production. It was found that the presence of hematite exsolutions and their grain size, twinning, the amount of ferric iron in the ilmenite, and the grain size distribution of the feed material affected the solubility of the ilmenite concentrate. Structural discontinuities, such as twinning, favoured the leaching of ilmenite grains. Depending on the size and distribution of exsolved hematite, there is a good correlation between the degree of dissolution of ilmenite and the amount of exsolved hematite from ilmenite. On the other hand, the coarser the ilmenite grain in the digestion step is the lesser the solubility. The quantity of trace elements, such as Cr and V, and their provenances in the mineral lattices normally affect the quality of the pigment. Their concentrations in the Tellnes ilmenite, however, are associated with the exsolved hematite which does not go into solution. Mg affects the precipitation process, and the MgO content of the concentrate is 4% which is mainly bound in ilmenite lattices. In contrast, MgO rises to 10% in unreacted solids due to the accumulation of insoluble Mg-bearing silicates.

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Der Effekt von Mineralogie und Textur auf den Produktionsprozeß von TiO₂ Pigmenten aus Ilmenit-Konzentraten von Tellnes

Zusammenfassung Die Mineralogie und die texturellen Beziehungen der Ilmenit-Konzentrate von Tellnes wurden untersucht, um den Effekt der mineralogischen Charakteristika des Rohmaterials auf die sulfatische TiO₂ Pigmetproduktion zu evaluieren. Es wurde herausgefunden, dass die Anwesenheit von Hämatit-Entmischungen und deren Korngröße, Verzwilligung, der Anteil an dreiwertigem Eisen im Ilmenit und die Korngrößenverteilung des aufgegeben Rohmaterials die Löslichkeit des Ilmenit-Konzentrates beeinflussen. Strukturelle Diskontinuitäten, wie etwa Zwillinge, begünstigen das Auslaugen der Ilmenitkörner. In Abhängigkeit von der Größe und Verteilung des entmischten Hämatits, gibt es eine gute Korrelation zwischen dem Grad der Auflösung von Ilmenit und der Menge an entmischtem Hämatit im Ilmenit. Andererseits sinkt die Löslichkeit von Ilmenit mit Zunahme der Korngröße. Die Gehalte an Spurenelementen, wie etwa Cr und V und ihre Provenienz in den Kristallgittern beeinflussen normalerweise die Qualität des Pigments. Im Tellnes Ilmenit sind sie allerdings an den entmischten Hämatit gebunden, der nicht in Lösung geht. Magnesium beeinträchtigt den Ausfällungsvorgang. Der MgO-Gehalt des Konzentrats ist 4% und ist überwiegend an das Ilmenitgitter geknüpft. Im Gegensatz dazu steigt, infolge der Akkumulation der unlöslichen Mg-führenden Silikate, der MgO-Gehalt auf 10% in den nicht reagierenden Festphasen au.

     

Mineralogical Characteristics of the Separated Magnetic Rutile of the Egyptian Black Sands

The Egyptian black sands contain several economic minerals, such as ilmenite, magnetite, garnet, zircon, rutile and monazite. During the concentration and separation of a high-grade rutile concentrate a bulk magnetic fraction is obtained. This fraction is composed mainly of opaques, titanhematite, ilmenite–titanhematite exsolved intergrown grains, magnetic leucoxene in addition to chromite, and magnetic rutile. The magnetic rutile occupies 6 wt.% of the bulk magnetic fraction or approx. 4 wt.% of the original rutile content in the raw sands. Most of magnetic rutile crystals are contaminated with opaque inclusions, staining-coating and/or composite locked grains. This magnetic rutile has a magnetic range from strongly paramagnetic to very weak paramagnetic. Electron microprobe analysis for twenty-three magnetic rutile grains identified mineral components of rutile, titanhematite, pseudorutile, leached pseudorutile and ilmenite in decreasing order of abundance. Some other inclusions are also detected in the different magnetic rutile grains. They are most probably garnet, silica, amphibole, ilmenite, feldspar, mica and zircon. The presence of these inclusions reflect the derivation of magnetic rutile of various crystalline igneous and metamorphic rocks. The magnetic susceptibility of magnetic rutile depends on the associated mineral components and their relative volumes in comparison to the rutile mineral component. Magnetic susceptibility of magnetic rutile is also related to both type and size of the associated mineral inclusions. The average chemical composition of the magnetic rutile is 66.34 wt.% TiO₂, 21.71 wt.% Fe₂O₃, 6.39 wt.% SiO₂, 1.80 wt.% Al₂O₃, 1.19 wt.% CaO and 0.10 wt.% Cr₂O₃. Thus, the contamination of magnetic rutile in the non-magnetic rutile concentrate would decrease the market value of the rutile concentrate. Alternatively these magnetic rutile grains are recommended to be blended with magnetic leucoxene or some types of ilmenite concentrate to improve the overall marketable specifications especially for both of Ti, Fe and Cr contents.     

峨眉山高钛玄武岩中主要的赋钛矿物——榍石的产状、特征及成因

峨眉山玄武岩中钛以什么矿物形式存在一直以来很少有学者提及。本文通过镜下观察、全岩化学分析、X-衍射、能谱、扫描电镜、电子探针、阴极发光对川西南部周公山-汉王场地区钻井岩心中峨眉山玄武岩进行了详细的分析,讨论了其主要赋钛矿物及成因。(1)SiO₂含量46.4%~48.3%和TiO₂>3%显示区内峨眉山玄武岩属于高钛峨眉山玄武岩系列。但多个层段榍石含量>5%,而极少见磁铁矿、钛铁矿;(2)榍石主要以隐晶质的云雾状、雪花状、芝麻点状、枝状等形态分布于微晶长石之间和溶孔、溶洞边缘及裂缝中,少量呈显晶质粒状分布于微晶长石、绿泥石之间。(3)电子探针分析显示:所有含钛矿物中,钛铁矿中TiO₂含量最高,为39.069%,榍石中TiO₂次之,TiO₂含量为17.143%~38.648%,磁铁矿中TiO₂含量最高为12.293%,平均在5%~10%左右,其他矿物基本上都少于1%。(4)扫描电镜及其能谱分析显示:榍石中的Ti含量(2.49%~24.97%)明显高于含钛磁铁矿(2.68%~9.21%)、含钛赤铁矿(3.64%)中Ti含量,与钛铁矿(19.51%)含量相当。分析结果认为:峨眉山玄武岩中大量出现的隐晶榍石可能是岩浆后期产物或期后蚀变的产物。在峨眉山玄武岩中首次鉴别出的大量隐晶质榍石是高钛峨眉山玄武岩中最主要的赋钛矿物。隐晶榍石在玄武岩中的含量是区分"高钛"和"低钛"玄武岩的主要标志之一。     

A hydrothermal investigation of the system FeOFe2O3TiO2: A discussion with new data

New experimental data on the system FeOFe₂O₂TiO₂ using a new oxygen buffer are presented. It is found that there is a narrow range of oxygen fugacity above 550°C within which hematite and ilmenite coexist stably.