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Ugarkar, A. G.
- Mineragraphy of Gold-quartz-Sulphide reefs of the Mangalur Greenstone Belt, Karnataka
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Authors
Affiliations
1 Department of Studies in Geology. Karnatak University, Dharwad 580003, IN
1 Department of Studies in Geology. Karnatak University, Dharwad 580003, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 33, No 6 (1989), Pagination: 576-582Abstract
Gold mineralization of gold-quartz vein-type is confined to narrow shear zones in the metabasic volcanic suite of the Mangalur Greenstone Belt. The dominant sulphide phase associated with the gold mineralization is pyrrhotite-pyrite assemblage followed by arsenopyrite, chalcopyrite and sphalerite in the decreasing order of abundance. Gold occurs in native state and within quartz.
- Ore Mineralogy of Western Auriferous Zone of Gadag Greenstone Belt, Karnataka
Abstract Views :192 |
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Authors
Affiliations
1 Department of Studies in Geology, Karnatak University, Dharwad 580003, Karnataka, IN
1 Department of Studies in Geology, Karnatak University, Dharwad 580003, Karnataka, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 43, No 5 (1994), Pagination: 549-555Abstract
Gadag greenstone belt, which has a history of ancient gold mining, hosts three distinct auriferous zones viz., Western Zone, Middle Zone and Eastern Zone distributed both in metavolcanic and metasedimentary suites. The paper presents ore mineralogy of the Western Auriferous Zone which is hosted by pillowed and sheared metavolcanic rocks. Based on the relative abundance of quartz veins and sulphide minerals this zone could be classified into Type-A ore and Type-B ore.
Type-A ore comprises white quartz veins (30-90 cms thick) displaying evidence of early deformations. They contain chloritic/micaceous leafy aggregates and traces of arsenopyrite, pyrite, chalcopyrite and sphalerite ± scheelite; gold occurs in native form in vein quartz.
Type-B ore comprises mainly chlorite-muscovite/sericite-ankerite-monazite sulphide schist with subordinate vein quartz. Associated sulphides are arsenopyrite, pyrite, pyrrhotite, chalcopyrite, sphalerite and galena in the orderof decreasing abundance. Scheelite is seen occasionally. Gold occurs as: (i) native gold in silicate and quartz gangue, (ii) native gold inclusions and microfracture fillings in arsenopyrite and (iii) in combined state in arsenopyrite. Arsenopyrite could serve as a main pathfinder mineral for exploration, mining as well as processing of Type-B ore.
Mineralogical characteristics, wall-rock alterations and structural features related to Type-A ore, Type-B ore and host rocks characterise the gold mineralisation in the Western Auriferous Zone as structure controlled hydrothermal epigenetic lode.
Keywords
Gold, Sulphides, Ore Mineralogy, Greenstone Belt, Gadag, Karnataka.- Mineralogy, Geochemistry and Genesis of Clay Deposits in Belgaum, Dharwad and Chitradurga Districts, Karnataka
Abstract Views :177 |
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Authors
Affiliations
1 Department of Studies in Geology, Karnatak University, Dharwad 580003, IN
2 Aerodynamic Research Center, P.O. Box 19584/449, Tehran, IR
1 Department of Studies in Geology, Karnatak University, Dharwad 580003, IN
2 Aerodynamic Research Center, P.O. Box 19584/449, Tehran, IR
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 44, No 2 (1994), Pagination: 157-165Abstract
A dozen clay deposits occurring in the districts of Belgaum, Dharwad and Chitradurga of Karnataka State have been studied. ln Dharwad district, while the clay deposits derived from greywackes/phyllites are dominated by kaolinite, those derived from the acid metavolcanics contain illite as the sole clay mineral. In Belgaum and Chitradurgadistricts the deposits are kaolinitic, characterised by poor crystallinity and near absence of illite.
Chemically, the clay deposits studied have relatively high silica and low titania. The transformation of precursor rocks to clay deposits which was brought about by insitu chemical weathering and subsequent reworking of the weathered products under tropical climatic conditions was accompanied by enrichment of Al, Zr and Cr and removal of Sit Fe. Ni, Cu and Zn. Presence of relicts of nearly all the major and accessory minerals native to the precursor rocks, in all the litho-units of clay profiles is in agreement with such an interpretation.
Keywords
Economic Geology, Clay, Geochemistry, Mineralogy Chitradurga, Dharwad, Belgaum, Karnataka.- Copper Mineralization in Machanur Area of the Dharwar Craton, Karnataka
Abstract Views :177 |
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Authors
Affiliations
1 Department of Studies in Geology, Karnatak University, Dharwad-580003, IN
2 Department of Environmental Science, Bangalore University, Bangalore- 560056, IN
1 Department of Studies in Geology, Karnatak University, Dharwad-580003, IN
2 Department of Environmental Science, Bangalore University, Bangalore- 560056, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 44, No 5 (1994), Pagination: 505-512Abstract
Copper mineralization in Machanur is confined to the fracture and breccia zone (shear zone) traversing mainly pink porphyritic granite of the Closepet granite suite (2,400-2,000 my.) including minor diabase dykes and pegmatites, The mineralization is fractule-controlled cavity filling epiigenetic hydrothermal type. The associated wall-rock alterations are chloritization, saussuritizalion, sericitization and silicification of the host-rocks. The mineralization consists essentially of chalcopyrite and pyrile with subordinate bornite, chalcocite, covellite, digenite and linnaeitc. Native copper occurs but rarely. Hematite(specularite) and magnetite are commonly associated with the mineralization. Three stages of mineralization have been inferred. It is suggested that the second stage has been dominated by precipitation of chalcopyrite. The paragenetic scquence is suggestive of high fO2 condition in fluid at the beginning and progressive increase of Cu/Fe ratio and high fS2 condition in fluid during the main Cu deposition stage.Keywords
Copper, Ore Mineralogy, Paragenesis, Economic Geology, Machanur, Karnataka.- Petrography and Geochemistry of the Neoarchaean Greywackes from Central Part of the Dharwar-Shimoga Greenstone Belt, Western Dharwar Craton
Abstract Views :485 |
PDF Views:217
Authors
Affiliations
1 Department of Studies in Geology, Karnatak University, Dharwad-580003, IN
2 Department of Geology, Central University of Kerala, Kasaragod-671123, IN
1 Department of Studies in Geology, Karnatak University, Dharwad-580003, IN
2 Department of Geology, Central University of Kerala, Kasaragod-671123, IN
Source
International Journal of Earth Sciences and Engineering, Vol 10, No 4 (2017), Pagination: 898-902Abstract
Greywackes are the most dominant of litho units in the central part of the Dharwar-Shimoga greenstone belt of the Western Dharwar Craton. They are texturally immature with angular to subangular detrital sand grains with 25 to 60% matrix. Quartz forms the main detrital component and is mostly monocrystalline with distinct undulatory extinction. Amongst feldspars, plagioclase feldspar exceeds K-feldspar. Micas occur as large and small flakes that are oriented. Biotite is the main mica mineral. The phyllite, chert, quartzite and felsic volcanic rock fragments are common. The matrix is generally made up of chlorite, sericite, clay to silt-sized quartz and feldspar. In Q-F-L classification diagram, these rocks plot in the fields of quartz wackes and quartzose wackes. The silica content varies between 60.93 and 68.07 wt% and alkalies between 3.69 and 5.21 (Table 2), and compositionally they are comparable to andesite and dacite. Moderately higher values of Fe2O3 (av. 8.16 wt%), MgO (av. 7.89 wt%) and K2O/Na2O (av. 1.65) indicate a matrix with an abundance of chlorite, biotite, clays and iron oxides. The petrographic and geochemical evidence suggests that these greywackes were derived from the source which had felsic to intermediate composition, with a moderate relief exposed to arid and dry palaeoclimatic conditions. As compared to greywackes of the northern part of the Dharwar-Shimoga greenstone belt, the greywackes of the present study area (central part) have higher values of MgO, Fe2O3+MgO, K2O/Na2O, Al2O3/Na2O and lower values of Al2O3, Na2O, and SiO2/MgO.Keywords
Greywacke, Petrography, Geochemistry, Provenance, Dharwar-Shimoga Greenstone Belt.Full Text
References
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- Basalt-Andesite-Dacite-Rhyolite (BADR) Metavolcanic Sequence from the Central Part of Dharwar-Shimoga Greenstone Belt, Western Dharwar Craton
Abstract Views :156 |
PDF Views:119
Authors
Affiliations
1 Department of Studies in Geology, Karnatak University, Dharwad-580003, IN
2 Department of Geology, Central University of Kerala, Kasaragod-671123, IN
1 Department of Studies in Geology, Karnatak University, Dharwad-580003, IN
2 Department of Geology, Central University of Kerala, Kasaragod-671123, IN
Source
International Journal of Earth Sciences and Engineering, Vol 10, No 1 (2017), Pagination: 106-110Abstract
The petrographic and major element geochemical characteristics clearly suggest that the metavolcanic rocks of Medur Formation in the central part of the Dharwar-Shimoga greenstone belt comprise basalt, andesite, dacite and rhyolite (BADR) sequence. These metavolcanic rocks are metamorphosed to greenschist-amphibolite facies. The basalts show mixed tholeiitic and komatiitic composition. The andesites are mainly tholeiitic, while dacite and rhyolites are calc alkaline nature. Good correlation exists between SiO2 and major oxides, which suggests that these metavolcanic series (BADR) compositions are genetically inter-related and were derived probably from differentiation of magma at different depths.Keywords
Metavolcanics, Petrography, Geochemistry, Dharwar-Shimoga Greenstone Belt, Dharwar Craton.Full Text
- Mineralogy and Geochemistry of Desur Clay Deposit Hosted Within the Peninsular Gneiss, Northern Part of the Dharwar Craton of South India
Abstract Views :115 |
PDF Views:121
Authors
T. B. Manuvachari
1,
R. L. Jayappagol
1,
S. R. Kulakarni
1,
N. A. Parry
1,
B. Chandan Kumar
1,
A. G. Ugarkar
1
Affiliations
1 Department of Geology, Karnatak University, Dharwad-580003, IN
1 Department of Geology, Karnatak University, Dharwad-580003, IN
Source
International Journal of Earth Sciences and Engineering, Vol 9, No 3 (2016), Pagination: 1012-1017Abstract
The clay deposit which is hosted within the Peninsular Gneisses at Desur in Belgaum District of Karnataka is underlain by partially weathered granitic gneiss and overlain by soil horizon. Infra-Red and major oxide composition of clay samples indicate that kaolinite is the dominant clay mineral with subordinate abundance of illite. Quartz, chlorite, muscovite and montmorillonite also occur, but in minor abundance as admixtures in these clays. Clays occur as non-linear horizontal bodies which do not support the hydrothermal process for their formation. While the observed gradation from top to bottom is soil, clays and a weathered zone with fragments of precursor rock and hard and compact gneiss, which essentially indicates in-situ development of the weathered or residual clay profile. Geochemical comparison of Desur clays with that of the host granitic gneiss reveals that SiO2, Fe2O3 CaO, Na2O and K2O oxides were mobile, while Al2O3 was immobile during the process of weathering. Kaolinite rich clay deposit of Desur was formed by the residual weathering of precursor granitic gneiss under tropical to sub-tropical humid conditions.Keywords
Clays, Residual Deposit, Peninsular Gneiss, Khanapur Granitic Pluton.Full Text
- Mineralogy and Geochemistry of Clay Deposit of Gadag Greenstone Belt, Dharwar Craton, India:Implications for Residual Deposition
Abstract Views :158 |
PDF Views:114
Authors
Affiliations
1 Department of Geology, Karnatak University, Dharwad-580003, IN
1 Department of Geology, Karnatak University, Dharwad-580003, IN
Source
International Journal of Earth Sciences and Engineering, Vol 9, No 1 (2016), Pagination: 110-115Abstract
The clay deposit occurs near Majjur-Varvi area, which is a large syncline, called as the Majjur syncline, bounded to the NE and SW by steep thrust faults, namely Sortur and Suganhalli discontinuities of the well-known Gadag greenstone belt, Dharwar Craton in southern India. The lowest part of the stratigraphy of this area comprises schistose metabasalts, followed by felsic metavolcanics, conglomerates and greywackes. The clay bodies occur within the felsic metavolcanic rocks. The X-Ray diffraction and Infra-Red studies indicate that kaolinite is the dominant clay mineral, with subordinate illite. Quartz and plagioclase are the associated minerals. The clays are characterized by higher contents of SiO2, CaO, Na2O, K2O, MgO and lower contents of Al2O3 compared to kaolinite mineral, which could be due to the presence of quartz, plagioclase and illite with these clays. Clays occur as non-linear horizontal bodies which do not support the hydrothermal process for their formation. While the cross sections in the quarries resemble shale. The observed gradation from top to bottom is soil, clays and a weathered zone with fragments of precursor rock, which essentially indicates in-situ development of the weathered or residual profile. Plagioclase was altered to clay while quartz was dissolved into solution and carried away from the site of weathering. Kaolinite clays in the study area occur as residual clay bodies that were formed by in-situ chemical weathering of felsic metavolcanics under tropical to sub-tropical humid and acidic conditions.Keywords
Clays, Residual Deposit, Gadag Greenstone Belt, Dharwar Craton.Full Text