Mantle heterogeneity in the source region of mid-ocean ridge basalts along the northern Central Indian Ridge (8°S-17°S)
| Autor: | Finlay M. Stuart, Jonguk Kim, Sang-Mook Lee, Sang-Joon Pak, Jai-Woon Moon, Jihye Oh |
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| Rok vydání: | 2017 |
| Předmět: |
Basalt
geography Radiogenic nuclide geography.geographical_feature_category 010504 meteorology & atmospheric sciences Geochemistry Mid-ocean ridge 010502 geochemistry & geophysics 01 natural sciences Mantle plume Mantle (geology) Geophysics Geochemistry and Petrology Oceanic crust Hotspot (geology) Transition zone Geology 0105 earth and related environmental sciences |
| Zdroj: | Geochemistry, Geophysics, Geosystems. 18:1419-1434 |
| ISSN: | 1525-2027 |
| DOI: | 10.1002/2016gc006673 |
| Popis: | 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 Reunion plume mantle, except for He isotopes. This suggests that the southern segments have incorporated a contribution of the fossil Reunion 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 Reunion 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 Reunion 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. |
| Databáze: | OpenAIRE |
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