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Do manganese nodules grow or dissolve after burial? Results from the Central Indian Ocean Basin

DRS at CSIR-National Institute of Oceanography

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Title Do manganese nodules grow or dissolve after burial? Results from the Central Indian Ocean Basin
 
Creator Pattan, J.N.
Parthiban, G.P.S.
 
Subject Buried nodules
Central Indian Ocean
Siliceous ooze
Red clay
 
Description Fifty buried manganese nodules at different depth intervals were recovered in 12 sediment cores from the Central Indian Ocean Basin (CIOB). A maximum of 15 buried nodules were encountered in one sediment core (AAS-22/GC-07) and the deepest nodule was recovered at 5.50 m below seafloor in core AAS-04/GC-5A. Approximately 80% of the buried nodules are small in size (approx. 2 cm diameter) in contrast to the Atlantic Ocean and Peru Basin (Pacific Ocean) where the majority of the buried nodules are large, approx. 8 cm and > 6 cm, respectively. Buried nodule size decreases with core depth and this distribution appears to be similar to the phenomenon of ‘Brazil Nut Effect’. Buried nodules exhibit both smooth and rough surface textures and are ellipsoidal, elongated, rounded, sub rounded, irregular and polynucleated. Buried nodules from siliceous ooze are enriched in Mn, Cu, Ni, Zn, Mo, Ga, V and Rb whereas those from red clay are enriched in Fe, Co, Ti, U, Th, Y, Cr, Nb and Rare Earth Elements (REE). Buried nodules from siliceous ooze suggest their formation under hydrogenetic, early digenetic and diagenetic processes whereas those from red clay are of hydrogenetic origin. REE are enriched more than 1.5 times in buried nodules from red clay compared to siliceous ooze. However, the mode of incorporation of REE into buried nodules from both sedimentary environments is by a single authigenic phase consisting of Fe-Ti-P. Shalenormalized REE patterns and Ce anomalies suggest that nodules from siliceous ooze formed under more oxidizing conditions than those from red clay. Nodules buried at depths between 1.5 and 2.5 m are diagenetic (Mn/Fe ratio 10-15), formed in highly oxic environments (large positive Ce anomalies) and record aeolian dust (high Eu anomalies). Chemical composition, surface texture and morphology of buried nodules are similar to those of surface nodules from the same basin. Furthermore, buried nodule compositions do not exhibit any distinct patterns within the core depth, suggesting that buried nodules neither grow nor dissolve after their burial in the sediment column.
 
Date 2007-07-25T07:21:58Z
2007-07-25T07:21:58Z
2007
 
Type Journal Article
 
Identifier Journal of Asian Earth Sciences, vol.30(5-6); 696-705p.
http://drs.nio.org/drs/handle/2264/636
 
Language en
 
Rights An edited version of this paper was published by Elsevier. Copyright [2007] Elsevier
 
Format 687360 bytes
application/pdf
 
Publisher Elsevier