Mantle heterogeneity in the source region of mid-ocean ridge basalts along the northern Central Indian Ridge (8°S-17°S)

Kim, J., Pak, S.-J., Moon, J.-W., Lee, S.-M., Oh, J. and Stuart, F. M. (2017) Mantle heterogeneity in the source region of mid-ocean ridge basalts along the northern Central Indian Ridge (8°S-17°S). Geochemistry, Geophysics, Geosystems, 18(4), pp. 1419-1434. (doi:10.1002/2016GC006673)

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Abstract

The northern Central Indian Ridge (CIR) between 8°S and 17°S is composed of seven segments whose spreading rates increase southward from ∼35 to ∼40 mm/yr. During expeditions of R/V Onnuri to study hydrothermal activity on the northern CIR in 2009–2011, high-resolution multibeam mapping was conducted and ridge axis basalts were dredged. The major and trace element and Sr-Nd-Pb-He isotopic compositions of basaltic glasses dredged from the spreading axis require three mantle sources: depleted mantle and two distinct enriched mantle sources. The southern segments have Sr, Nd, and Pb that are a mix of depleted mantle and an enriched component as recorded in southern CIR MORB. This enrichment is indistinguishable from Rèunion plume mantle, except for He isotopes. This suggests that the southern segments have incorporated a contribution of the fossil Rèunion plume mantle, as the CIR migrated over hot-spot-modified mantle. The low 3He/4He (7.5–9.2 RA) of this enriched component may result from radiogenic 4He ingrowth in the fossil Rèunion mantle component. Basalts from the northern segments have high 206Pb/204Pb (18.53–19.15) and low 87Sr/86Sr (0.70286–0.70296) that are distinct from the Rèunion plume but consistent with derivation from mantle with FOZO signature, albeit with 3He/4He (9.2–11.8 RA) that are higher than typical. The FOZO-like enriched mantle cannot be attributed to the track of a nearby mantle plume. Instead, this enrichment may have resulted from recycling oceanic crust, possibly accompanied by small plume activity.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Stuart, Professor Finlay
Authors: Kim, J., Pak, S.-J., Moon, J.-W., Lee, S.-M., Oh, J., and Stuart, F. M.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Geochemistry, Geophysics, Geosystems
Publisher:American Geophysical Union
ISSN:1525-2027
ISSN (Online):1525-2027
Published Online:07 April 2017
Copyright Holders:Copyright © 2017 American Geophysical Union
First Published:First published in Geochemistry, Geophysics, Geosystems 18(4): 1419-1434
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

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