Multiscale chemical heterogeneities beneath the eastern Southwest Indian Ridge (52°E–68°E): Trace element compositions of along‐axis dredged peridotites
| Type | Article | ||||||||
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| Date | 2011-09 | ||||||||
| Language | English | ||||||||
| Author(s) | Seyler Monique1, Brunelli Daniele2, 3, 4, Toplis Michael J.5, Mevel Catherine6 | ||||||||
| Affiliation(s) | 1 : Univ Lille 1, CNRS FRE 3298, UFR Sci Terre, F-59655 Villeneuve Dascq, France. 2 : Univ Modena, Dipartimento Sci Terra, I-41100 Modena, Italy. 3 : ISMAR CNR, I-40129 Bologna, Italy. 4 : IPGP CNRS UMR 715, F-75238 Paris 05, France. 5 : Univ Toulouse 3, CNRS UMR5277, Inst Rech Astrophys & Planetol, F-31400 Toulouse, France. 6 : Univ Paris Diderot, CNRS UMR 7154, Inst Phys Globe Paris, F-75005 Paris 05, France. |
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| Source | Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2011-09 , Vol. 12 , N. 9 , P. Q0AC15 | ||||||||
| DOI | 10.1029/2011GC003585 | ||||||||
| WOS© Times Cited | 47 | ||||||||
| Keyword(s) | Indian Ocean, abyssal peridotite, mantle heterogeneities, trace elements, ultraslow spreading ridge | ||||||||
| Abstract | The Southwest Indian Ridge is characterized by frequent outcrops of mantle rocks in a very slow spreading context. In situ measurements of trace element concentrations in pyroxenes of these rocks, and associated petrogenetic modeling, are reported. Overall, the measured compositions cover the whole range typically observed for abyssal peridotites. The greatest subkilometer-scale compositional variability is observed in the region east of the Melville fracture zone. The best explanation for the observed variability is given by concurrent melting and migration of melts strongly enriched in the most incompatible rare earth elements, such as those produced by a garnet-bearing source, or by refertilization with mixed garnet- and spinel-derived partially aggregated melts. Because the regionally associated basalts bear no “garnet signature” in their chemical compositions, we conclude that the residual mantle preserves the signature of a mantle source component that does not appear in the erupted magmas. Comparison between along-axis variations of basalt isotopic compositions and peridotite chemical compositions suggests that local isotopic enrichments displayed by some basalts can be associated with the “garnet signature” in the peridotite and that our sampling represents only a fraction of the global variability of the subaxial mantle. To the west of the Melville fracture zone, samples are more depleted and homogeneous at dredge scale. In addition to containing enriched components, petrologic modeling indicates that the peridotitic mantle beneath the entire section underwent (previous?) partial melting in the garnet stability field before melting at lower pressures. | ||||||||
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