Record Details

Geochemical implications of gabbro from the slow-spreading Northern Central Indian Ocean Ridge, Indian Ocean

DRS at CSIR-National Institute of Oceanography

View Archive Info
 
 
Field Value
 
Title Geochemical implications of gabbro from the slow-spreading Northern Central Indian Ocean Ridge, Indian Ocean
 
Creator Ray, Dwijesh
Misra, S.
Banerjee, R.
Weis, D.
 
Subject Gabbro
sediments
Indian Ocean
depleted mantle
 
Description Gabbro samples (c. < 0.4 Ma old) dredged from close to the ‘Vityaz Megamullion’ on the slow-spreading Northern Central Indian Ridge (NCIR, 18-22 mm yr sup(-1)) include mostly olivine gabbro and Fe-Ti oxide gabbro. The cumulate olivine gabbro shows ophitic to subophitic texture with early formed plagioclase crystals in mutual contact with each other, and a narrow range of compositions of olivine (Fo sup(80-81)), clinopyroxene (magnesium number: 85-87) and plagioclase (An sub(67-70)). This olivine gabbro could be geochemically cogenetic with the evolved oxide gabbro. These gabbro samples are geochemically distinct from the CIR gabbro occurring along the Vema, Argo and Marie Celeste transform faults and can further be discriminated from the associated NCIR basalts by their clinopyroxene (augite in gabbro, and diopsidic in basalts) and olivine (gabbro: Fo sub(80–81), basalts: Fo sub(82–88)) compositions. Our major oxide, trace element and REE geochemistry analyses suggest that the gabbro and the NCIR basalts are also not cogenetic and had experienced different trends of geochemical evolution. The clinopyroxenes of the present NCIR gabbros are geochemically similar to primitive melt that is in equilibrium with mantle peridotite, and do not show any poikilitic texture with resorbed plagioclase; these results negate the possibility of these gabbros being a pre-existing cumulate that has been brought up to the shallower oceanic crust and interacted with the NCIR basalt. The Sr, Pb and Nd isotopic data of the gabbro substantially differ from those of the NCIR basalts and suggest significant contamination of the depleted mantle source of the gabbro, most likely by the Indian Ocean pelagic sediments. The Pb-isotope data suggest that the proportion of pelagic sediment that mixed in the depleted mantle source of the NCIR gabbro is much higher than the level of contamination observed for the Indian Ocean MORBs
 
Date 2011-04-08T10:53:13Z
2011-04-08T10:53:13Z
2011
 
Type Journal Article
 
Identifier Geological Magazine, vol.148(3); 2011; 404-422
http://drs.nio.org/drs/handle/2264/3834
 
Language en
 
Rights An edited version of this paper was published by © Cambridge University Press 2010
 
Publisher Cambridge University Press