Evidence for major-element heterogeneity in the mantle source of abyssal peridotites from the Southwest Indian Ridge (52 degrees to 68 degrees E)
| Type | Article | ||||||||
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| Date | 2003-02-06 | ||||||||
| Language | English | ||||||||
| Author(s) | Seyler M1, 2, 3, 4, Cannat M2, 3, 4, Mevel C2, 3, 4 | ||||||||
| Affiliation(s) | 1 : Univ Lille 1, UFR Sci Terre, F-59655 Villeneuve Dascq, France. 2 : Univ Paris 06, CNRS, UMR 7097, Lab Geosci Marines, F-75252 Paris 05, France. 3 : Univ Paris 07, CNRS, UMR 7097, Lab Geosci Marines, F-75252 Paris 05, France. 4 : Inst Phys Globe, F-75252 Paris 05, France. |
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| Source | Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2003-02-06 , Vol. 4 , N. 2 , P. 1-33 | ||||||||
| DOI | 10.1029/2002GC000305 | ||||||||
| WOS© Times Cited | 139 | ||||||||
| Note | Supporting Information : http://onlinelibrary.wiley.com/doi/10.1029/2002GC000305/suppinfo | ||||||||
| Keyword(s) | peridotite, midocean ridge, Indian Ocean, petrology, mantle heterogeneity, geochemistry : composition of the mantle, marine geology and geophysics : midocean ridge processes, information related to geographic region : Indian Ocean, history of geophysics : volcanology, geochemistry, and petrology | ||||||||
| Abstract | A suite of 53 samples of mantle spinel lherzolites and harzburgites dredged at 13 sites between 52degreesE and 68degreesE along the Southwest Indian Ridge has been studied for petrography and mineral major element chemistry. Results show that the residual mantle beneath this very slow-spreading/cold ridge is strongly heterogeneous in modal and mineral compositions at local and regional scales and underwent greater extents of melting than predicted by melting model and by compositions of the basalts dredged with the peridotites. Along-axis, the peridotite compositional variability defines a concave pattern with increasing depletion at both ends of the studied section (e. g., approaching Rodrigues Triple Junction to the East and Gallieni fracture zone to the west) that cannot be matched with the basalt compositions. Clinoyroxenes reflect depleted compositions (low modal abundances, high Cr and Mg, low Ti contents) but are paradoxally enriched in jadeite component, a feature that distinguishes these peridotites from common abyssal peridotites. Textural data show that major depletion in basaltic components and pyroxene Na enrichment are early features of the studied peridotites. In most samples, Na is nevertheless correlated with Ti suggesting that initial clinopyroxenes had high Na/Ti contents. Samples at both ends of the studied area have even higher Na/Ti ratios because of higher Na enrichment and higher Ti depletion, indicating metasomatic interaction. We conclude that along-axis compositional variations characterizing these peridotites are primary controlled by major element heterogeneity in the initial mantle, that have been preserved because of low degrees of melting beneath the Southwest Indian Ridge. | ||||||||
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