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Hutti, Hira Buddini, Uti |
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Karnataka, India |
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Au
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Super Porphyry Cu and Au
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The Hutti gold mine lies within the Precambrian Dharwar Schist Belt of Karnataka State in western India, some 400 km NNW of the Kolar gold field. Modern mining commenced in 1904, with 22.5 tonnes of gold having been produced by 1988. Head grades have ranged from 19.5 g/t Au in 1920 to 6.5 g/t Au in 1986. Some 300 ancient workings are evident along strike from Hutti in the 70 km long Hutti-Muski Belt of Dhawar Schists. Hira Buddini and Uti are satellite mines of the Hutti operation.
The Dhawar Schists, which are surrounded by granite-gneiss complexes were derived from a greenstone sequence of interbedded metabasalts, meta-sediments and cherts which are believed to be of late Archaean age and equivalents of the hosts at the much larger Kola deposit.
Nine auriferous lodes have been recognised at Hutti, six of which have been commercially exploited. These lodes are quartz veins enclosing parallel to sub-parallel, narrow, linear layers of chlorite-biotite schist. They are localised within narrow zones of strongly sheared chlorite-biotite schist. The veins contain free gold, sulphides (pyrite, arsenopyrite, sphalerite, galena, chalcopyrite, pyrrhotite) and oxides in a gangue of quartz, chlorite, biotite, sericite, actinolite, hornblende, tourmaline, calcite, siderite and ankerite.
Gold mineralisation at Hutti took place on a metamorphic retrograde path commencing with initial alteration (and sulphidation) at upper greenschist facies. After a protracted phase of fluid evolution, the mineralisation culminated in the formation of laminated auriferous quartz veins at lower greenschist facies. In the observed D1 to D5 deformation sequence, the proximal biotite alteration zones, containing isoclinally folded quartz veins (D2) and the laminated fault-fill veins (D3) are auriferous.
Gold is considered to have been deposited between 2586 ±59 Ma (the imprecise magmatic age of the Hutti-Maski greenstone belt) and 2543 ±9 Ma the syn-D3 intrusion
age of the Kavital granitoid that cuts the ore.
Hira Buddini, like Hutti, is situated in the Hutti-Maski Greenstone Belt of the Archean Dharwar Craton. It is some 25 km south of Hutti. Gold mineralisation occurs in a narrow, ENE-trending, steep dipping reverse, brittle-ductile shear zone and shallow-dipping, sigmoidal extension veins at the lithological contact of metabasalt, -dacite and Đgabbro. Within the shear zone, amphibolite facies gold mineralisation is largely restricted to the selvages of quartz and calcite bearing lenticular extension veins, and to the altered host rocks. The initial of mineralisation is overprinted by second stage gold during strike slip reactivation of the shear zone at greenschist facies conditions. In the metabasalt, there is both a distal and proximal alteration zone. Metamorphic hornblende is replaced by chlorite and tourmaline in the former, and by actinolite, biotite and tourmaline within the latter. Plagioclase is altered to more calcic varieties during the alteration process. Pyrite and chalcopyrite are the only sulphide minerals associated with the gold mineralisation.
The Uti gold mine is 20 km NE of Hutti. Total production + reserves + resources are thought to total around 4 Mt @ approx. 2.8 g/t Au. The deposit is very similar to that at Hutti.
The Hutti group of deposits has total resources + reserves of approximately 150 Mt @ 4 g/t Au to a depth of 3000 m (Sarma et al., 2008)
For detail see the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 2008.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
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Selected References:
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Kolb J, Rogers A and Meyer F M 2005 - Relative timing of deformation and two-stage gold mineralization at the Hutti Mine, Dharwar Craton, India: in Mineralium Deposita v40 pp 156-174
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Kolb J, Rogers A, Meyer F M and Siemes H, 2005 - Dominant coaxial deformation of veins during the interseismic stage of the fault-valve cycle: microfabrics of laminated quartz veins of the Hutti gold mine, India : in J. of Structural Geology v27 pp 2043-2057
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Kolb J, Rogers A, Meyer F M, Vennemann T W 2004 - Development of fluid conduits in the auriferous shear zones of the Hutti Gold Mine, India: evidence for spatially and temporally heterogeneous fluid flow: in Tectonophysics v378 pp 65-84
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Krienitz M S, Trumbull R B, Hellmann A, Kolb J, Meyer F M and Wiedenbeck M, 2008 - Hydrothermal gold mineralization at the Hira Buddini gold mine, India: constraints on fluid evolution and fluid sources from boron isotopic compositions of tourmaline: in Mineralium Deposita v43 pp. 421-434
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Mishra B and Pal N, 2008 - Metamorphism, Fluid Flux, and Fluid Evolution Relative to Gold Mineralization in the Hutti-Maski Greenstone Belt, Eastern Dharwar Craton, India: in Econ. Geol. v103 pp 801-827
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Mishraa B, Palb N and Sarbadhikaria A B 2005 - Fluid inclusion characteristics of the Uti gold deposit, Hutti-Maski greenstone belt, southern India : in Ore Geology Reviews v26 pp 1-16
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Naganna C 1987 - Gold mineralization in the Hutti mining area, Karnataka, India: in Econ. Geol. v82 pp 2008-2016
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Pal N, Mishra B 2002 - Alteration geochemistry and fluid inclusion characteristics of the greenstone-hosted Gold deposit of Hutti, eastern Dharwar Craton, India: in Mineralium Deposita v37 pp 722-736
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Pandalai H S, Jadhav G N, Mathew B, Panchapakesan V, Raju K K, Patil M L 2003 - Dissolution channels in quartz and the role of pressure changes in gold and sulfide deposition in the Archean, greenstone-hosted, Hutti gold deposit, Karnataka, India: in Mineralium Deposita v38 pp 597-624
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Sarma DS, McNaughton N J, Fletcher IR, Groves D I, Mohan MR and Balaram V, 2008 - Timing of gold mineralization in the Hutti gold deposit, Dharwar craton, south India: in Econ. Geol. v103 pp 1715-1727
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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