Competitive Exams: Indian Geography gold

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Gold

  • Hutti Mines and Kolar Gold Fields(Karnataka)

  • Ramagiri: Andhara Pradesh

  • Wynad: Kerala

  • Nilgiri: TN

The total in situ reserves of gold ore are estimated at 22.4 million tonnes, with 116.5 tonnes of metal. India’s contribution to world gold production is an insignificant 0.75 per cent. The gold production of South Africa is 60 times, of Canada 22 times and of Australia is 5 time than that of India.

Gold evolves as a siderophile element from the iron-nickel core at crustal spreading centers. During partial melting of the mantle, gold along with metals derived from sulphides rise with basaltic (magmatic) fluids into the crust along mid-oceanic ridges and at subduction zones. It is then associated with complex processes involving convection, subduction, partial melting, hydrothermal processing, weathering, erosion and deposition before being returned to the mantle for recycling again at subduction centers. The deep-seated ore bearing solutions containing gold are of both magmatic and metamorphic origin. The temperature, pressure, pH, salinity, redox, and sulphur content hydrothermal fluids influence the metal carrying capacity.

Geochronological data of gold metallogeny revealed major periods of enrichment as Archaean and Proterozoic. Gold occurs in a variety of litho assemblages, and multiple geological environments / settings such as greenstone belts, mantle derived intrusions, diaperic juvenile plutons, and granulites. In the Indian subcontinent, prominent granite greenstone belts of Peninsular Sheild are located in Dharwar, Bastar, Singhbhum and Rajasthan cratons. The Dharwar craton, with two blocks viz the eastern and western, hosts the maximum number of gold occurrences. The Eastern block provides an important and favourable lithologic, structural, and stratigraphic milieu for gold mineralization and hosts major deposits like Kolar and Hutti.

In the northwestern Indian Shield, gold occurs in association with copper in the Archaean greenstone-like sequence (at Dhani Basri, in Mangalwar Complex) and Proterozoic metavolcanosediments (at Bhukia and Dugocha, in Aravalli Supergroup) with enrichment in the latter. Gold also occurs in Palaeo / recent river alluvium placers, laterite, soil and regolith. Puga geothermal system is a “ hot spring type epithermal gold deposit in the making, in the Ladakh region of Jammu and Kashmir.