Geochemistry of Iron Ores

Geochemical process of selective concentration of elements is controlled by the dynamic tectonic evolution of earth in the geological time scale of million of years. Iron crystallizes out from magmatic melt if the evolved basal-tic melt is highly enriched with Fe (high chemical activ-ity of Fe) and suitable pressure temperature (thermo-dynamic) condition to stabilize spinel magnetite and ilmen-ite. Iron is soluble in atmospheric EhpH conditions and is amenable to precipitate as hydroxide, oxyhydroxide, carb-onate and sulphide in localized change in Eh-pH. The sili-cate minerals weather to release Fe which precipitates as goethite, chamosite, siderite, pyrite in sedimentary geochemical environment depending upon the low-temperature thermodynamics prevailing in the depositional site. The phase transition to magnetite andhematite is also possi-ble during metamorphism and martitisation. So, concen-tration of iron in geological set up can occur in widely varied conditions from lacustrine to marine, even magmatic to metamorphic.While sedimentary iron deposit is assoc-iated with sedimentary rocks and to their metamorphic equivalent in case the terrain is metamorphosed, the mag-matic iron deposit is associated with basalt and meta-basalt. It is also suggested that hydrothermal action can selectively leach out carbonate-silicate metasediments with supergene enrichment of Fe. Majority of the iron ore deposits (Fig.- 5.1) are confined to Banded iron formation (BIF) of Proterozoic volcano-sedimentary sequence (supra-crustal) of age 2.5-2.4Ga, 2.2 - 2.06Ga and 2.0Ga. Thus, Complex genetic process has a control over the mineral-ogical and geochemical attribute of the iron ore, associ-ated rocks and their host rocks. The associated rocks contribute to the gangue component, which is the interest of Mineral Engineering to get rid of. The geochemical data also helps to understand the ore, its' utility and recov-ery of valuable metals if any

Analysis of direct CP violation in B−→D0Ds−,D0D−B^- \to D^0 D_s^-, D^0 D^- decays

We investigate the possibility of observing the direct CP violation in the decay modes $B^- \to D^0 D_s^-$ and $D^0 D^-$ within the Standard Model. Including the contributions arising from the tree, annihilation, QCD as well as electroweak penguins with both time- and space-like components, we find that the direct CP asymmetry in $B^- \to D^0 D_s^-$ is very small $\sim 0.2$ % but in $B^- \to D^0 D^-$ decay it can be as large as 4%. Approximately $10^7$ charged $B$ mesons are required to experimentally observe the CP asymmetry parameter for the later case. Since this is easily accessible with the currently running B factories, the decay mode $B^- \to D^0 D^-$ may be pursued to look for CP violation.Comment: Latex, 14 page

Titanate-Zircon-Apatite Bearing Diorite-Monzodiorites and their Resource Potentiality

Placer beach sand deposits are considered as the reserve for ilmenite, rutile, zircon, monazite, xenotime. The global reserve for titanium, zirconium and rare earth metals is accounted from the distribution of these miner-als in the beach sand. It is proposed to look into Archean diorites and monzodiorites as the potential resource for these minerals. These rocks contain sphene, ilmenite, zircon and apatite in trace amount but account for about 3 wt% of TiO,, 700 ppm of Zr, and about 500-800 ppm of rare earth in bulk. The mineralogical and geochemical characteristic of such rocks is discussed. The potentia-lity of sphene as a resource for titanium is highlighte

Feasibility of producing sinter fines from a low grade and fine grained hematite-goethitic ore

Iron ore quality in India is deteriorating due to continual increase in consumption of good grade ores. It is imperative to use low grade iron ores to meet the current demand. In the Jharkhand-Odisha belt hematite ore containing significant amount of goethite material have difficulty in processing. In the present paper, response of a low grade hematite-goethitic iron ore to beneficiation for the production of sinter and pellet feed material has been investigated. The ore sample contained hematite as the major iron bearing mineral with considerable amount of goethitic material. The major impurities present were quartz and clay. The sample contained reasonable amount of hematitic with relatively coarse liberation, however, overall the sample was poorly liberated. This posed difficulty in producing concentrate with desired metallurgical performance. The modified strategy involved selectively recovering sinter fines with possible recovery of pellet grade material. Hence, the top size of the ore was kept at 5 mm and ore was subjected to scrubbing and washing, followed by classification. Beneficiation studies such as jigging, tabling and WHIMS were carried out on different washed products and results are discussed. A total of 32% with Fe 63.8% sinter material and a varied amount of pellet material could be achieved from low grade iron ore

Nanometer Thick Microplaty Hematite in Indian Iron Ores: Its Implication on Washing

Occurrence of nanometer to submicron thick microplaty hematite in the iron ore of eastern India is reported for the first time. High grade soft laminated ore and biscuity ore contain randomly oriented microplaty hematite along porous lamellae and pseudo-foliation planes. These microplaty hematites have a thickness of 70 nm to 500 nm or more. The thicker ones also show cleavage planes within, indicating the possibility of generating nanometer thick flakes. These microplaty hematites bridge the lamellae/laminae and interlamellar zones providing strength to the ore. On gentle tapping or by scrubbing with water, the ore breaks to fragments and fines of free microplaty hematite. On washing, the microplaty hematite grains get liberated and washed out to fine fraction of -150 m. It results in the fines of higher grade and low alumina in comparison to the associated lumps. It carries importance in the washing circuits using such ore types as feed

Amenability to Processing of Maganiferous Iron Ore

Manganiferous iron ore from Karnataka state was investi-gated to upgrade the iron content with lowering of mang-anese in concentrate. Mineralogical studies show that it is comprised of microplaty hematite, martite, goethite, pyrolusite, cryptomelane and minor amount of quartz and kaolinite. The sample contains about 51.4% Fe, 4.75% Mn with 8.5% SiO2 and 2.8% Al2O3. The crushed to 1mm and 3mm samples were subjected to reduction roasting using produ-cer gas. The reduction roasting converts the hydrated iron oxide mineral into more magnetic materials which facilita-tes the magnetic separation at low intensity leaving manganese minerals in non-magnetic. The reduced products were subjected to magnetic separation at very low magnetic field to recover magnetite. The final concentrate contain-ing 64.1% Fe and 2.3% Mn is achieved with a yield of 73.5% from -1mm sample. This product can be blended with the low Mn- hematitic concentrate with 65% Fe to generate a pellet feed

Recovery of Iron Values from Waste Manganiferous Iron Ore Fines for Pellet Making

A large volume of overburden and mine wastes is generated during the extraction and beneficiation of the low grade ores. The waste low grade manganiferous iron ore fine from southern part of India was studied for recovery of iron values. The chemical assay of the sample is 52.36% Fe, 4.75% Mn, 8.5% SiO2 and 2.82% Al2O3. The characterization study of the sample indicates the presence of microplaty hematite, goethite, pyrolusite, cryptomelane with minor amount of quartz and kaolinite. The beneficiation study of the sample does not respond to the conventional route of desliming the ground feed followed by gravity separation and magnetic separation. Therefore, an alternative technique of reduction roasting using a producer gas was attempted at different conditions. The characterization of roasted product reveals the phase transformation to magnetite and microplaty magnetite. The low intensity magnetic separation conducted with the roasted products generated at optimal condition shows that 70% concentrate having 64.5% Fe and 1.87% Mn could be produced. The high manganese in the concentrate works as an additive for making pellet with enhancement in pellet strength and drop in reducibility. Utilization of mines waste has significant impact on mineral resources and environmental hazard

Effect of mineralogy and texture on the strength of iron ore

A preliminary investigation on three types of iron ore from the same deposit was carried out. Major minerals in all the three ores are dense martite, microplaty hematite, vitreous goethite, ochreous goethite at varied proportion whereas kaolinite and quartz occur in minor to trace amount. There is a textural variation with micro-porosity. The strength is the maximum (674 kg.f/cm2) in the ore dominated by dense martite and pseudotachylite whereas moderately low (254 kg.f/cm2) in the ore with micro-platy hematite and extensive micro-porosity, and is the lowest (157 kg.f/cm 2) for the ore dominated by goethite. Presence of pseudotachylite, reported for the first time, in dense martite iron ore possibly provides additional strength to the latter

Surface Chemical and Settling Studies on Hematite, Quartz and Kaolinite in Presence of Organic Reagents

The industrial practice of beneficiation of iron ores produces substantial amount of slimes which causes loss of iron values and environmental pollution. Slimes consists of extremely fine grained iron bearing minerals, impurities and poses problem in processing by conventional beneficiation techniques. The present study aims to develop flocculation technique for selective separation of iron bearing mineral from slimes. Initial experiments were directed towards understanding surface chemical properties of constituent minerals viz. hematite, quartz and kaolinite with or without organic reagents such as tannic acid, starch and polyacrylamide-co-acrylic acid (m.w.-150 lakh). In this paper, the results of flocculation-dispersion experiments on individual samples of hematite, quartz and kaolinite are discussed as a function of different process parameters such as pH, flocculation time and dosages of reagents. Based on the studies, conditions were established for selective separation of hematite from quartz and kaolinite. The results of flocculation-dispersion of individual minerals were applied to ternary synthetic mineral system