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Nayak P.K.,Orissa Mining Corporation Ltd | Mohapatra B.K.,CSIR - Institute of Minerals And Materials Technology | Singh P.P.,Utkal University | Martha R.K.,CSIR - Institute of Minerals And Materials Technology
Resource Geology | Year: 2011

Banded iron formation (BIF) comprising high grade iron ore are exposed in Gorumahisani-Sulaipat-Badampahar belt in the east of North Orissa Craton, India. The ores are multiply deformed and metamorphosed to amphibolite facies. The mineral assemblage in the BIF comprises grunerite, magnetite/martite/goethite and quartz. Relict carbonate phases are sometimes noticed within thick iron mesobands. Grunerite crystals exhibit needles to fibrous lamellae and platy form or often sheaf-like aggregates in linear and radial arrangement. Accicular grunerite also occur within intergranular space of magnetite/martite. Grunerite needles/accicules show higher reflectivity in chert mesoband and matching reflectance with that of adjacent magnetite/martite in iron mesoband. Some grunerite lamellae sinter into micron size magnetite platelets. This grunerite has high ferrous oxide and cobalt oxide content but is low in Mg- and Mn-oxide compared to the ones, reported from BIFs, of Western Australia, Nigeria, France, USA and Quebec. The protolith of this BIF is considered to be carbonate containing sediments, with high concentrations of Fe and Si but lower contents of cobalt and chromium ± Mg, Mn and Ni. During submarine weathering quartz, sheet silicate (greenalite) and Fe-Co-Cr (Mg-Mn-Ni)-carbonate solid solution were formed. At the outset of the regional metamorphic episode grunerite, euhedral magnetite and recrystalized quartz were developed. Magnetite was grown at the expense of carbonate and later martitized under post-metamorphic conditions. With the increasing grade of metamorphism greenalite transformed to grunerite. © 2011 The Authors. Resource Geology © 2011 The Society of Resource Geology.


Mohapatra B.K.,CSIR - Institute of Minerals And Materials Technology | Mishra S.,Orissa Mining Corporation | Singh P.P.,Utkal University
Journal of the Geological Society of India | Year: 2012

Outcrop of wad, about 3-5 m thick, associated with low to medium-grade manganese ore deposits in Iron Ore Group (IOG), is present in large quantum in Bonai-Keonjhar belt, Orissa. It is often inter-bedded with volcanic ash layers. Wad is powdery, fine grained, black to blackish-brown in colour, very soft, readily soils the fingers and its hardness on the Mohs' hardness scale is 1-3. The wad zone is capped by a thin lateritic zone and overlies manganese ore beds of variable thickness in Dalki, Guruda and Dubna mines. Wad constitutes two mineral phases, viz. manganese oxides (δ-MnO 2, manganite, romanechite with minor pyrolusite) and iron oxides (goethite/limonite and hematite) with minor clay and free quartz. Mixed limonite-clay and cryptomelane-limonite are commonly observed. Under microscope the ore appears oolitic, pisolitic, elipsoidal to globular in shape having small detritus of quartz, pyrolusite / romanechite and hematite at the core. The ore contains around 23% Mn and 28% Fe with ∼7% of combined alumina and silica. Wad might have developed in a swampy region due to slow chemical precipitation of Fe-Mn-Co enriched fluid, nucleating over quartz/hematite grains. Influence of a marine environment is indicated from δ-MnO 2 phase. Remnants of some microfossils, like algal filament, bacteria, foraminifera and diatomite are observed in wad sample under SEM. These microorganisms might have been responsible for the oxidation of dissolved Mn 2+ and Fe 2+ precipitates. These findings suggest biochemogenic origin of wad in Bonai-Keonjhar belt of Orissa. © 2012 Geological Society of India.


Nayak P.K.,Orissa Mining Corporation Ltd | Mohapatra B.K.,CSIR - Institute of Minerals And Materials Technology | Singh P.P.,Utkal University
Resource Geology | Year: 2014

Banded iron formation (BIF) of the Gorumahisani-Sulaipat-Badampahar (GSB) belt in Singhbhum Craton, India, consists predominantly of magnetite. This BIF is intruded by a magnetite dyke. The magnetite dyke is massive and compact with minor sulphide minerals while the host banded magnetite ore, a component of the BIF, shows thin lamination. The magnetite ore of the dyke is fine to medium grained and exhibits interlocking texture with sharp grain boundaries, which is different from the banded magnetite that is medium to coarse grained and show irregular martitised and goethitised grain boundaries. Relics of Fe-Ca-Mn-Mgcarbonate and iron silicates (grunerite and cummingtonite) are observed in the banded magnetite. The intrusive magnetite is distinctly different in minor, trace and REE geochemistry from the banded magnetite. The banded magnetite contains higher amounts of Si, Al, Mn, Ca, Mg, Sc, Ga, Nb, Zr, Hf, Co, Rb and Cu. In contrast, the massive magnetite is enriched in Cr, Zn, V, Ni, Sr, Pb, Y, Ta, Cs and U with higher abundance of HREE. In the chondrite normalized plot, the massive magnetite shows a slight positive Eu anomaly while the banded ore does not show any Eu anomaly. Field disposition, morphology, mineralogy and chemistry show that the intrusive magnetite dyke is of igneous origin, while magnetite in BIF formed from a carbonate protolith through the process of sedimentation. © 2014 The Society of Resource Geology.


Subrat M.,Orissa Mining Corporation | Kumar M.B.,Orissa Mining Corporation | Nilima D.,Orissa Mining Corporation | Srinivas R.D.,Orissa Mining Corporation
Mining Science and Technology | Year: 2011

Low grade siliceous manganese ores from the iron ore group of the Bonai-Keonjhar belt, Orissa, India are found mostly in shear zones. The ore characteristics of siliceous manganese ore samples from three different mines, viz. the Shankar (BarbilOMC lease hold area), the Sone-Patuli (Patmunda,OMMlease hold area), and the Musaghar (Roida,OMDClease hold area), were studied. These siliceous manganese ores are of three types, respectively: (i) spongy-granular; (ii) massive-mosaic; and (iii) hard-mylonitized. The spongy-granular type contains granular, saccharoidal quartz and the major manganese mineral present is pyrolusite. The second type contains well crystallized quartz and cryptomelane, while the third has cherty, fine grained quartz (mylonite) along with romanechite. All three ores were subjected to physical beneficiation under similar conditions. Both gravity and magnetic separation techniques were employed. The mineral-fabric of the ores has been correlated to the extent of their beneficiation using these physical techniques. Of these three ores only the spongy-granular type responded well to upgrading. The feed with 22%Mncontent could be upgraded to 44% with a 28% yield and a 49% recovery. The good response to beneficiation of the spongygranular sample could be due to the large euhedral crystals of pyrolusite and the friable nature of the saccharoidal quartz. This study reveals the influence of mineral-fabric on beneficiation of low grade ore, siliceous Mn ore in particular. © 2011 Published by Elsevier B.V. on behalf of China University of Mining & Technology.

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