| Registro completo |
| Provedor de dados: |
ArchiMer
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| País: |
France
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| Título: |
Melt extraction and mantle source at a Southwest Indian Ridge Dragon Bone amagmatic segment on the Marion Rise
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| Autores: |
Gao, Changgui
Dick, Henry J. B.
Liu, Yang
Zhou, Huaiyang
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| Data: |
2016-03
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| Ano: |
2016
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| Palavras-chave: |
Abyssal peridotite
Mid-ocean ridge basalt
Previous melting
Buoyant upper mantle
Marion Rise
The Dragon Bone amagmatic segment
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| Resumo: |
This paper works on the trace and major element compositions of spatially associated basalts and peridotites from the Dragon Bone amagmatic ridge segment at the eastern flank of the Marion Platform on the ultraslow spreading Southwest Indian Ridge. The rare earth element compositions of basalts do not match the pre-alteration Dragon Bone peridotite compositions, but can be modeled by about 5 to 10% non-modal batch equilibrium melting from a DMM source. The Dragon Bone peridotites are clinopyroxene-poor harzburgite with average spinet Cr# similar to 27.7. The spinet Cr# indicates a moderate degree of melting. However, CaO and Al2O3 of the peridotites are lower than other abyssal peridotites at the same Mg# and extent of melting. This requires a pyroxene-poor initial mantle source composition compared to either hypothetical primitive upper mantle or depleted MORB mantle sources. We suggest a hydrous melting of the initial Dragon Bone mantle source, as wet melting depletes pyroxene faster than dry. According to the rare earth element patterns, the Dragon Bone peridotites are divided into two groups. Heavy REE in Group 1 are extremely fractionated from middle REE, which can be modeled by similar to 7% fractional melting in the garnet stability field and another similar to 12.5 to 13.5% in the spinet stability field from depleted and primitive upper mantle sources, respectively. Heavy REE in Group 2 are slightly fractionated from middle REE, which can be modeled by similar to 15 to 20% fractional melting in the spinet stability field from a depleted mantle source. Both groups show similar melting degree to other abyssal peridotites. If all the melt extraction occurred at the middle oceanic ridge where the peridotites were dredged, a normal similar to 6 km thick oceanic crust is expected at the Dragon Bone segment. However, the Dragon Bone peridotites are exposed in an amagmatic ridge segment where only scattered pillow basalts lie on a partially serpentinized mantle pavement. Thus their depletion requires an earlier melting occurred at other place. Considering the hydrous melting of the initial Dragon Bone mantle source, we suggest the earlier melting event occurred in an arc terrain, prior to or during the closure of the Mozambique Ocean in the Neproterozoic, and the subsequent assembly of Gondwana. Then, the Al2O3 depleted and thus buoyant peridotites became the MORB source for Southwest Indian Ridge and formed the Marion Rise during the Gondwana breakup.
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| Tipo: |
Text
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| Idioma: |
Inglês
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| Identificador: |
https://archimer.ifremer.fr/doc/00421/53262/54680.pdf
https://archimer.ifremer.fr/doc/00421/53262/54682.pdf
https://archimer.ifremer.fr/doc/00421/53262/54693.xlsx
DOI:10.1016/j.lithos.2015.12.007
https://archimer.ifremer.fr/doc/00421/53262/
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| Editor: |
Elsevier Science Bv
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| Formato: |
application/pdf
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| Fonte: |
Lithos (0024-4937) (Elsevier Science Bv), 2016-03 , Vol. 246-247 , P. 48-60
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| Direitos: |
2015 Elsevier B.V. All rights reserved.
info:eu-repo/semantics/openAccess
restricted use
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