Geology and Genesis of the Major Banded Iron Formation-Hosted High-Grade Iron Ore Deposits of India
Joydip Mukhopadhyay, Jens Gutzmer, N. J. Beukes, Harendra Nath Bhattacharya, 2008. "Geology and Genesis of the Major Banded Iron Formation-Hosted High-Grade Iron Ore Deposits of India", Banded Iron Formation-Related High-Grade Iron Ore, Steffen Hagemann, Carlos Alberto Rosière, Jens Gutzmer, Nicolas J. Beukes
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With a current annual production of about 170 million tons (Mt), India is the sixth largest producer of high-grade iron ore (>60 wt % of Fe) in the world. The greater part of the high-grade iron ores of India (>5 billion tons reserve base) are hosted by voluminous banded iron formations of major Archean greenstone belt successions. Major deposit districts include (1) the Noamundi-Koira Valley of the Singhbhum craton of eastern India, (2) the Bailadila-Dalli-Rajhara deposits of the Bastar craton in central India, (3) the Donimalai-Hospet deposits, as well as (4) the Goa deposits of the Eastern and Western Dharwar cratons, respectively, in southern India. The present investigation was carried out to compile, augment and interpret information on the geologic setting, mineralogy, petrography, and geochemistry of the most important districts. Results reveal that high-grade iron ore deposits in the major Indian ore districts have characteristics that are similar to many other high-grade BIF-hosted iron ore deposits worldwide. Close correspondence exists in particular with iron ore deposits regarded to be of supergene-modified hydrothermal origin, in particular those of the giant Serra dos Carajás district (Brazil). Hard ores rich in hematite and martite in most of the Indian deposits are believed to have formed during early hydrothermal events. Chemical weathering in wet tropical humid-monsoonal climate resulted in extensive supergene modification of these hydrothermally upgraded iron ores and surrounding BIF to soft saprolitic hematite-martite ores, as well as the development of surficial goethitic ores. The proposed genetic model leads to the conclusion that currently known high-grade hard hematite-martite ore deposits in India might persist to greater depth than currently envisaged, and that deposits of soft and friable hematite-martite ore might, at depth, be underlain by high-grade magnetite-rich hard ore or, alternatively, by hydrothermally altered BIF.