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Kudremukh, Bababudam Hill, Gangamula |
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Karnataka, India |
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Fe
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Kudremukh magnetite iron deposit in the Chikmagalur District is located in the Aroli-Gangamula range of the Western Ghats, 50 km north-east of the Arabian Sea port of Mangalore in south-western Karnataka State of western India. Other key deposits in the district include Bababudam Hill and Gangamula.
The iron ores are hosted by the late Meso- to Neoarchaean 3.0 to 2.6 Ga Dharwar Supergroup supracrustal rocks which overlie and are infolded into a Mesoarchaean 3.3 to 3.0 Ga basement in the Western Dharwar craton. The 500 x 300 km, NNW-SSE elongated Western Dharwar craton is bounded to the west by the Arabian Sea; to the east by the linear NNW west zone of tectonic activity occupied by the 2.5 to 2.3 Ma Closepet Granite complex separating it from the Eastern Dhawar craton; to the north by the blanket of Cretaceous to Tertiary Deccan basalts; and to the south by the transition to the granulite facies charnockite-khondalite rocks that occupy the tip of the Indian Peninsular.
The basement within the craton and at Kudremukh is represented by 3.4 to 2.9 Ma granitic (tonalite to tronhjemite) gneisses and granodiorites of the Peninsular Gneiss, with scattered enclaves of the older Sargur supracrustals, largely composed of high grade mafic to ultramafic rocks.
The late Meso- to Neoarchaean Dharwar Supergroup supracrustals have changing facies from east to west, as follows:
i). An amphibolite facies sequence of paragneiss-metaarkose interbedded with calcsilicates and quartzites with some banded iron formations. These rocks appear to be structurally (thrust faulted) separated (east side up) from the next belt to the west.
ii). A 450 km long NNW-SSE trending belt of greenschist facies rocks commencing with a quartz pebble conglomerate unit at the base, overlain by a sequence of metabasic rocks with intercalated quartzite and schist, discordantly followed by a thicker succession of basic and minor acid volcanic rocks with intercalated alternating banded ferruginous quartzite and accompanying phyllite. These are in turn succeeded by phyllites and metapelitic schists and greywackes, including conglomerates, ferruginous quartzites and volcanic rocks.
iii). a basin like area to the west of the southern section of the previous belt, with a succession that commences with a quartz pebble conglomerate, overlain by meta-basaltic rocks, intercalated with local crossbedded quartzites and conglomerates, overlain by banded ferruginous cherts interbedded with phyllites, then more metabasaltic rocks and interbedded phyllites, followed by conglomerates passing laterally into phyllites and crossbedded quartzites.
iv). The most extensive belt to the west is also generally of greenschist facies, extends NNW-SSE and includes the Kudremukh district towards its southern margin. It comprises basalt, andesite and dacitic volcanic rocks, greywackes conglomerates and iron formations with localised zones of gabbro-anorthosite and ultramafic intrusions. In the Kudremukh district the sequence there is an apparent older layered mafic complex overlain by an older volcano-sedimentary succession of ultramafic and mafic rocks (dated at 3 Ga) with thin mica schists and current bedded, ripple marked quartzites. These are overlain by greywackes, shales/phyllites, carbonates, banded iron formation and mafic to acid volcanics and some conglomerates. All of these rocks have locally been multiply deformed and metamorphosed to amphibolite facies.
In the Kudremukh district there are two types of magnetite banded iron formation (BIF), namely:
Cherty BIF - contain alternating microbands of quartz and iron oxide (predominantly magnetite) minerals;
Shaly BIF - which comprise altenating layers of magnetite, microcrystalline chert/quartz and a higher content of minute bands of amphibole (actinolite, cummingtonite, grunerite, riebeckite and minor aegirine) layers in addition to the quartz and iron oxide bands and yield elevated Al2O3 levels. Minor calcite/dolomite and rarely biotite have also been observed.
The ore deposits are primary or slightly enriched magnetite-quartzite BIFs and cover an area of 4 to 6 x 1.7 km, within 3 beds distributed over a stratigraphic interval of 30 to 50 m.
Resource and reserve figures and estimates from a variety of sources include:
~1.0 Gt @ 38% Fe - resource in the Kudremukh-Nellibeedu-Gangrikal deposits;
430 Mt @ 38% Fe which is upgraded to 63% Fe pellets for export (original mineable reserves in current Kudremukh mines);
195 Mt @ 38% Fe - total production to 1997.
Iron formations elsewhere throughout the Dharwar Supergroup supracrustals have been tested and moderate reserves with grades similar to, and smaller tonnages of grades higher than those at Kudremukh have been indicated.
The most recent source geological information used to prepare this decription was dated: 2006.
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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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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