Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

B. K. Mohapatra ¹, R. Natarajan ², A. K. Paul ³, R. K. Sahoo ¹

Affiliations
1 Regional Research Laboratory, Bhubaneswar 751 013, IN
2 National Geophysical Research Institute, Hyderabad 500 007, IN
3 Department of Geology, Utkal University, Bhubaneswar 751 004, IN

Abstract

Minute discrete grains of rutile present in manganese ores of Dengura, Koira valley, Sundergarh district, exhibit imperfect columnar and crystallographic forms and an outstanding illustration of twinning. EPMA and EDAX results indicate the presence of Fe, Mn, Cr, Al, Ba, K and Ta, Nb in minor proportion, in rutile crystals. Some of these clements are either present in limited solid solution or later got introduced into its structure during late epigenetic processes. These are detrital grains, pre-existing in the host shale and later affected by solution during epigene manganese are formation.

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B. K. Mohapatra ¹, A. K. Paul ², R. K. Sahoo ¹

Affiliations
1 Regional Research Laboratory, Bhubaneswar 751013, Orissa, IN
2 P. G. Department of Geology, Utkal University, Bhubaneswar 751004, Orissa, IN

Abstract

The paper records small-scale primary and secondary structures in different tuffaceous rocks of Barsua Valley, Sundargarh district, Orissa, India. The tuffs of acid, basic and intermediate composition are structurally both isotropic and anisotropic and form a part of the sheet-like tuff-tufflava-lava sequence of the Precambrian Iron-Ore Volcanics.

The primary bedding structures like tuff layers and laminations. cross-lamination and graded-bedding; secondary (deformational) structures like small-scale polyphase folds, their interference structures and associated boudins; distinctive structures, viz., small-scale faults etc. are described. Pre-tectonic soft sediment deformational structures are obscured by the imprint of tectonic structures.

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J. K. Mohanty ¹, R. K. Sahoo ¹

Affiliations
1 Regional Research Laboratory, Bhubaneswar 751013, IN

Abstract

Chemical composition as well as different iomc ratios of chrome spinels of Beula-Nausahi ultramafic body, Orissa, have been determined. These data tell about the nature of original magma and temperature and oxygen fugacity of chromite crystallization. These data when compared with other well-known chromite deposits of the world, reveal a stratiform mode of origin for the deposit.

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B. K. Mohapatra ¹, A. K. Paul ², R. K. Sahoo ²

Affiliations
1 PG Department of Geology, Utkal University, Bhubaneswar 751 004, Orissa, IN
2 Scientists, Regional Research Laboratory, Bhubaneswar 751 013, Orissa, IN

Abstract

Petrographic studies of pyritiferous tuff forming a part of Precambrian lron-Ore Volcanics of Bausuan valley, Sundergarh district, Orissa, reveal interesting textural peculiarities of pyrite. The three textural varieties: framboidal, colloform banded and recrystallized appear both in composite association and as independent units in highly carbonatized tuff. In composite association, the frarnboidal variety constitutes more or less the central part of the globules of colloform banded pyrite (gel pyrite) which in turn is enveloped at the periphery by discontinuous crusts of recrystallized variety. Different intermediate textures of pyrite are described and variations in reflectivity, microhardness, etch behaviour and elemental distribution visMaavis the varieties have been discussed. Average Co/Ni ratio along with the textural manifestations of the pyrite attests its sedimentary origin. Different stages of process of formation of textural varieties are also briefly outlined.

Keywords

Ore Mineralogy, Framboidal Pyrite, Sulphide Mineralization, Barsuan, Orissa.

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B. C. Acharya ¹, D. S. Rao ¹, R. K. Sahoo ¹

Affiliations
1 Regional Research Laboratory, Bhubaneswar 751013, IN

Abstract

Manganese ores of Nishikhal occur as distinctly conformable bands in the khondalite suite of rocks. Presence of phosphorus, iron and silica beyond desirable limit in most of the ores makes them unsuitable for industrial purposes. The dominant ore minerals are psilornelane, cryptomelane, pyrolusite and goethite. These ores are formed by supergene enrichment of primary syngenetic metamorphosed assemblages. Phosphorus is present as a discrete mineral phase in the form of apatite contained in the silicate minerals, as well as fixed in the crystal structure of goethite, cryptomelane and psilomelane. Physical beneficiation may be employed to remove the silicate minerals which will ultimately reduce a part of phosphorus. Removal of iron by this method may be difficult because of the fine grain-size and complex intergrowth with goethite.

Keywords

Economic Geology, Manganese, Koraput, Orissa, Khondalite.

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B. C. Acharya ¹, S. K. Das ¹, R. K. Sahoo ¹, B. C. Patnaik ², N. K. Das ³

Affiliations
1 Regional Research Laboratory, Bhubaneswar 751 013, IN
2 Directorate of Mines, Govt. of Orissa, Bhubaneswar, IN
3 Orissa Remote Sensing Application Centre, Bhubaneswar, IN

Abstract

Tin along with Nb and Ta occurs both as primary mineral in pegmatites and as detrital mineral in the colluvial, eluvial and alluvial placers in Matili-Mundaguda area of Koraput District, Orissa. Cassiterite is commonly associated with soda plagioclase, microcline, perthite, quartz and muscovite, and it invariably contains inclusions of columbite-tantaIite, tapiolite, pyrochlore and fergusonite varying from 0.4 to 18% by volume and 3 to 400 microns in size. Minerals, like ilmenite, magnetite, lepidolite, pyrite, chalcopyrite and sphalerite are also associated with cassiterite. Nb and Ta is present in cassiterite both in solid solution as well as separate mineral phases.

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B. K. Mohapatra ¹, A. K. Paul ², R. K. Sahoo ¹

Affiliations
1 Regional Research Laboratory, Bhubaneswar, Orissa, IN
2 P. G. Department of Geology, Utkal University, Bhubaneswar, Orissa, IN

Abstract

The Kusumdih ore bodies are lentiformal being interbanded and co-folded with the shale formation of Iron Ore Group and are surficially lateritised. They are of lateritoid type.

Presence of manganese minerals like cryptomelane. pyrolusite, psilomelane, lithiophorite, manganite, coronadite (?), chalcophanite and braunite type is established. Iron is present in three oxy-hydroxide phases, viz., hematite, goethite and lepidocrocite. Cryptomelane and pyrolusite are ubiquitous in all the varieties. Lithiophorite as vug filling occurs in appreciable quantity in laminated and colloform banded varieties. Occurrence of psilomelane and coronadite is also recorded in some varieties. Manganite associated and intergrown with pyrolusite is observed. Hematite and maghemite (?) form the bulk of the ore minerals in manganiferous shale, alongwith subordinate amount of kaolinite and cryptomelane.

Fabrics of different ore minerals observed indicate colloform, replacement, banded. veined, open-space filling, brecciated and intergrowth textures. More than one generations of cryptomelane, pyrolusite, manganite and goethite are recognised. Mineral association of higher oxyhydroxides of manganese and the textural characteristics attest a low-temperature formation of syngenetic sedimentary ore bodies later subjected to oxidation/solution processes during weathering in the zone of lateritisation.

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B. K. Mohapatra ¹, S. K. Misra ¹, R. K. Sahoo ¹

Affiliations
1 Regional Research Laboratory, Bhubaneswar 751013, IN

Abstract

This note is aimed at elucidating the relationship between morphology and chemistry of some ferromanganese samples of Central Indian Ocean basin and describing precisely the factors controlling these variations. The samples investigated were dredged from Central Indian Ocean basin at a depth of 4000-5000 m during cruises of SS Fernela (St. F₄ and F₅), SS Scandy Surveyor (St. SS₄, SS₅, SS₆ and SS₈) and RV Sagarkanya (St. SK₈) conducted by the National Institute of Oceanography, Goa. Because of certain restrictions, location of sample details have not been mentioned.

Keywords

Marine Geology, Ferromanganese Nodules, Indian Ocean.

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S. K. Das ¹, R. K. Sahoo ¹, J. Muralidhar ¹, B. K. Nayak ¹

Affiliations
1 Regional Research Laboratory, Bhubaneswar-751013, Orissa, IN

Abstract

In the Sukinda ultramafic belt of Orissa, significant deposits of nickeliferous laterite have formed by weathering of large chromiferous dunite-peridotite suite of rocks. Two typical laterite profiles obtained by drilling (BH-1 = 50 m and BH-2 = 46 m) from Kansa sector of Sukinda belt were studied in order to establish petrochemical relationships between supergene Ni-laterites and the parent rock. In BH-1, ferruginous layers comprise the profile where goethite is intimately admixed with quartz, kaolinite and gibbsite at various depths. In BH-2, a complete laterite profile from bed rock (altered dunite) to top pisolitic laterite with transitional clay-serpentinite zone is encountered. The altered dunite is essentially composed of olivine (FO_93.8 ≅ 35% vol.) and serpentine. The clay-serpentinite zone consists of varying proportions of smectite clay (nontronite) and antigorite with minor amount of chromite, goethite and quartz. This zone is enriched in Ni with a maximum value of 1.09% Ni. In the ochreous ferruginous zone overlying clay-serpentinite zone, serpentine and nontronite disappear completely and goethite constitutes the principal mineral with varying proportions of secondary quartz. This zone is rich in Fe, Ni, Co, Mn, Al and Cr and is formed by residual concentration of stable oxides. Mass-balance equation assuming Cr₂O₃ as constant chemical constituent reveals that nickel is strongly accumulated in the clay-serpentinite zone. A second maximum in nickel concentration is found in ochreous ferruginous zone with almost complete removal of magnesium. Normalised major and trace element data generated on the bore hole samples have been processed, by using R-mode factor analysis of correlation matrix to understand the natural process of weathering. Leaching studies of the samples suggest that nickel occurs in adsorbed state within amorphous hydrated iron oxide and in weakly bonded and lattice bound states within gaethite and secondary silicates.

Keywords

Economic Geology, Geochemistry, Nickeliferous Laterite, Leaching, Sukinda, Orissa.

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D. S. Rao ¹, B. C. Acharya ¹, R. K. Sahoo ¹

Affiliations
1 Regional Research Laboratory (CSIR), Bhubaneswar-751013, IN

Abstract

No Abstract.

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B. K. Nayak ¹, B. C. Acharya ¹, R. K. Sahoo ¹

Affiliations
1 MM Division, Regional Research Lab., Bhubaneswar-751 013, IN

Abstract

Complex system of geochemical variables obtained from manganese ores of Balaghat mine, M.P., is simplified by using R-mode factor analysis of correlation matrix. Eighteen major oxides and trace elemental variable have been expressed in terms of the three common (rotated) factors and genetic interpretations of these factors have been brought out in relation to the manganese deposit.

Keywords

Factor Analysis, Manganese Ore, Balaghat, Madhya Pradesh.

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J. K. Mohanty ¹, R. K. Sahoo ¹, A. K. Paul ²

Affiliations
1 Regional Research Laboratory, Bhubaneswar - 751 013, IN
2 Dept. Geology, Utkal University, Bhubaneswar, IN

Abstract

During Serpentinization of the ultramafic rocks, the accessory chrome spinels are altered at grain margins and/or along fractures to highly reflecting phases of ferritchromit and magnetite which occur as rims around parent chromite. Of these two altered phases, ferritchromit exhibits greater compositional variation. Electron probe microanalysis data indicate that these phases are rich in Fe and poor in Cr, Al and Mg with respect to parent chromite. Magnetite rim is characterised by extreme iron enrichment and marked depletion of Cr, Al and Mg whereas ferritchromit represents intermediate chemical composition between parent chromite and the magnetite outer rim. This compositional variation is due to solid state diffusion of elements from chromite outwards during serpentinization. Textural features, chemical composition and presence of chromiferous serpentine attest genetic relationship between serpentinization and chromite alteration.

Keywords

Economic Geology, Chromite Alteration, Mineral Chemistry, Boula-Nausahi, Orissa.

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J. K. Mohanty ¹, R. K. Sahoo ¹

Affiliations
1 Regional Research Laboratory, Bhubaneswar - 751 013, IN

Abstract

The ultramafic rocks of Boula-Nausahi igneous complex have undergone extensive alteration resulting in the development of serpentinites. Petrographic and mineralogical observations have led to the recognition of two stages of mineral formation. The first stage (retrograde metamorphism) is characterised by complete transformntion of magmatic olivine to lizardite and the second stage (prograde metamorphism) in the formation of antigorite and alteration of accessory chrome spinels. Mineral assemblages indicate serpentinization to be a low temperature oxidation phenomenon. Formation of magnetite, ferritchromit and sulphide minerals is controHed by oxygen and sulphur fugacities prevalent during the process of serpentinization. Mineralogy, chemistry and geological setting of the serpentinites indicate an isochemical nature of the serpentinization process.

Keywords

Economic Geology, Mineralogy, Serpentinites, Orissa.

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S. K. Das ¹, R. K. Sahoo ¹, A. K. Paul ², G. Friedrich ³

Affiliations
1 Regional Research Laboratory, Bhubaneswar - 751 013, IN
2 Department of Geology, Utkal Universty, Bhubaneswar - 751 004, IN
3 Institut fuer Mineralogie und Lagerstattenlehre der RWTH, Aachen, DE

Abstract

Minor amount of Mn oxides occur as veins and fracture fillings in some of the chromite ore samples of D-Quarry of South Kaliapani, Sukinda. Microscopic, XRD and EPMA studies indicate that the Mn oxide minerals are lithiophorite and chalcophanite. These minerals are enriched in Ni and Co and were formed by lateritic weathering of ultramafic rocks.

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B. K. Nayak ¹, Swati Mohanty ¹, Rajeev ¹, R. K. Sahoo ¹

Affiliations
1 Regional Research Laboratory, Bhubaneswar-751013, IN

Abstract

Normalised major and trace element data of manganese ores from Nishikhal are processed by using R-mode factor analysis of correlation matrix. Twenty major and trace elemental variables are expressed in terms of 3 common (rotated) factors to understand the mineralogical occurrences and the processes of formation of the manganese deposit. Varimax factor scores are used to classify in a finer detail the manganese ore types.

Keywords

Factor Analysis, Geochemistry, Manganese Ore, Orissa.

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B. K. Mohapatra ¹, B. R. Nayak ¹, R. K. Sahoo ¹

Affiliations
1 Minera10gy and Meta110graphy Division, Regional Research Laboratory, Bhubaneswar - 751 013, IN

Abstract

Characteristics of vernadite in manganese ores from Gangpur Group of rocks, Goriajhor Formation, Sundargarh district, Orissa, have been described. This terrestrial vernadite is distinguished from δ-MnO₂ in marine manganese nodules by its well ordered crystallinity and thinner fibrils of submicron size. It appears to be chemically homogenous with the proposed formula: (Ba, K, Fe) MnO₂.nH₂O. This vernadite probably originated through solution, precipitation and redeposition under supergene conditions and later transformed into cryptomelane or romanechite.

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S. K. Das ¹, B. K. Nayak ¹, P. Chattopadhyay ¹, J. Muralidhar ¹, B. B. Nayak ¹, A. K. Singh ², R. K. Sahoo ³

Affiliations
1 Regional Research Laboratory, Bhubaneswar - 751 013, IN
2 2N3/278, IRC Village, Bhubaneswar - 751 015, IN
3 137, Jagganath Vihar, Bhubaneswar - 751 003, IN

Abstract

At Gopur, Onssa, auriferous quartz veins with stringers and rich disseminations of sulphides occur in the latcntes derived by tropical weathering of metabasaltic rocks. Minute to coarse irregular gold grains were hand picked from the panned heavies obtained by washing the excavated wall rock materials of the quartz veins which are composed of powdery latente ± kaolinite ± quartz. The gold grains display pitted, fractured, striated, wavy surface and occasional smooth contour pattern. The gold content of the quartz veins and latentic wall rocks vanes widely from < 1 ppm to 9 ppm SEM-EDS and microprobe analytical results of four gold grains reveal contrasting chemical characters. One gold gram exhibits nmward increase in fineness value indicating that silver has been preferentially leached out by supergene fluid. This grain possibly represents the residually concentrated hypogene gold. The other gold grains do not show chemical gradients within the domain of individual gram and formed by precipitation from supergene fluids.

Keywords

Gold, Supergene Mineralisation, Vein Quartz, Latentcs Fineness, Gopur, Orissa.

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