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The Indian Ocean Nodule Field: Petrotectonic evolution and ferromanganese deposits

DRS at CSIR-National Institute of Oceanography

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Title The Indian Ocean Nodule Field: Petrotectonic evolution and ferromanganese deposits
 
Creator Mukhopadhyay, R.
Iyer, S.D.
Ghosh, A.K.
 
Subject tectonics
ferromanganese nodules
seamounts
submarine volcanoes
mineral resources
structural geology
 
Description The crust of the Indian Ocean Nodule Field (IONF), in the Central Indian Ocean Basin (10 degrees-16 degrees 30 minutes; 72 degrees-80 degrees E) and hosting the world's second largest and second highgrade manganese nodule deposit, formed between 60 and 49 Ma under three variable spreading conditions. Since two decades, an area 0.4x106 km super(2) has been surveyed and a huge geophysical data set and geological samples were collected. Several seamounts, hills and ridge-normal and ridge-parallel lineations have disturbed the seafloor that formed because of variable rate of spreading and formation of new oceanic crust along the ridge crest, during more than one episode of India-Eurasia collision. Based on nature of ridge-parallel lineations the IONF is divided (north to south) into sectors A and C that formed at a fast rate of spreading (90-95 mm/year, half-rate) and B and D that formed at an intermediate (55 mm/year) and slow (26 mm/year) rates, respectively. Tensional stress in A and C caused asymmetrical flexures, widely spaced faults and folds with low amplitude and large wavelength while flexures in D are closely spaced, long, symmetrical and of high amplitude. The timing and intensity of collision of India with Eurasia is constrained by variable intensity of these flexures suggesting probably a 'soft' touch at approx. 58 Ma and hard collision at approx. 51 Ma. Distribution, morphology and growth patterns of a majority of seamounts are linked to spreading rate. In the IONF tholeiitic basalts, spilites, ferrobasalt and pumice occur, the alteration of some has resulted in palagonite and zeolites. The IONF crust witnessed intraplate volcanism as seen from young rocks at the seamounts' base, inconsistent growth of seamounts, eruption of ferrobasalt in high amplitude magnetic zones and presence of volcanogenic-hydrothermal materials (approx. 10 ka age). In the last 8 Ma, FeMn deposits (nodules, crusts) formed at an average water depth of 5000 m. Hydrogenous precipitation primarily contributed metals while secondary intraplate eruption, subsurface igneous activity and diagenetic remobilisation enhanced growth and abundance of the deposit. Considering the contribution of various physico-chemical parameters, authors' propose a model for formation of the IONF FeMn deposits.
 
Date 2008-08-03T10:43:17Z
2008-08-03T10:43:17Z
2002
 
Type Journal Article
 
Identifier Earth Science Reviews, Vol. 60; 67-130p.
http://drs.nio.org/drs/handle/2264/1348
 
Language en
 
Rights Elsevier
 
Publisher Elsevier