Show simple item record

dc.contributor.authorRay, Dwijesh
dc.contributor.authorMisra, S.
dc.contributor.authorBanerjee, R.
dc.contributor.authorWeis, D.
dc.date.accessioned2011-04-08T10:53:13Z
dc.date.available2011-04-08T10:53:13Z
dc.date.issued2011
dc.identifier.citationGeological Magazine, vol.148(3); 2011; 404-422
dc.identifier.urihttp://drs.nio.org/drs/handle/2264/3834
dc.description.abstractGabbro 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
dc.language.isoen
dc.publisherCambridge University Press
dc.rightsAn edited version of this paper was published by © Cambridge University Press 2010
dc.subjectGabbro
dc.subjectsediments
dc.subjectIndian Ocean
dc.subjectdepleted mantle
dc.titleGeochemical implications of gabbro from the slow-spreading Northern Central Indian Ocean Ridge, Indian Ocean
dc.typeJournal Article


Files in this item

Thumbnail

This item appears in the following Collection(s)

Show simple item record