Deep segregation and crystallization of ultra-depleted melts in the sub-ridge mantle.
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| Title: | Deep segregation and crystallization of ultra-depleted melts in the sub-ridge mantle. |
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| Authors: | Ferrando, C.1,2 (AUTHOR) carlotta.ferrando@unige.it, Borghini, G.3 (AUTHOR), Sani, C.1 (AUTHOR), Genske, F.4 (AUTHOR), Ligi, M.5 (AUTHOR), Stracke, A.4 (AUTHOR), Sanfilippo, A.1,6 (AUTHOR) |
| Source: | Chemical Geology. Jan2024, Vol. 644, pN.PAG-N.PAG. 1p. |
| Subjects: | Melt crystallization, Mid-ocean ridges, Lithosphere, Isotopic signatures, Pyroxenite |
| Abstract: | Partial melting of mantle peridotite from which considerable amounts of melt have been extracted during prior melting episodes generates melts characterized by low incompatible element contents and very low ratios of highly to moderately incompatible elements, so-called 'ultra-depleted' melts. Reaction of peridotite with percolating ultra-depleted melts has been inferred from petrological-geochemical studies of abyssal peridotites and ophiolites. But so far, direct evidence for the existence of ultra-depleted melts, only comes from rare melt inclusions. Here, we show that a pyroxenite layer within abyssal peridotite from the Mid Atlantic Ridge (8°N, Doldrums Fracture Zone) formed by crystallization of a segregated melt that is highly depleted in incompatible elements, at >27 km-depth beneath the ridge axis (at T ∼ 1250 °C), and with little or no modification by interaction with the host harzburgite. During exhumation, the pyroxenite experienced decompression and partial re-equilibration under plagioclase-facies conditions (∼1060 °C and ∼ 15 km depth). The high Hf isotope ratio (εHf = 40.3) of the pyroxenite clinopyroxene is inherited from a melt sourced from an ultra-depleted peridotite that evolved with high Lu/Hf. The associated MORB-like Nd isotope ratios (εNd = 10.6), however, imply a long-term evolution of the source peridotite with composition moderately depleted in incompatible elements (rather low Sm/Nd). These compositions are different from the host harzburgite, but typical for peridotites that have melted and partially reacted with migrating melts in ancient times. Hence, the pyroxenite investigated here is a partial melt from an ultra-depleted peridotite that has become re-enriched in incompatible elements and clinopyroxene. This melt crystallized in the oceanic lithosphere, and partially re-equilibrated at low pressure during exhumation. Overall, our results show that renewed melting of ultra-depleted peridotites with a complex history of prior melting and melt-rock reaction occurs, and that such melts migrate through the sub-ridge mantle, and can thus contribute to mid ocean ridge magmatism, although to a still unknown extent. • Abyssal pyroxenite hold the isotopic signature of the parental melt mantle source. • Doldrums pyroxenite records melting of ancient ultra-depleted, refertilized mantle. • Refertilization enables melting of otherwise ancient refractory mantle. • Segregation shortly after melt generation preserves trace of ultra-depleted melts. [ABSTRACT FROM AUTHOR] |
| Copyright of Chemical Geology is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.) | |
| Database: | Engineering Source |
| FullText | Text: Availability: 0 |
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| Header | DbId: egs DbLabel: Engineering Source An: 174496365 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: Deep segregation and crystallization of ultra-depleted melts in the sub-ridge mantle. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Ferrando%2C+C%2E%22">Ferrando, C.</searchLink><relatesTo>1,2</relatesTo> (AUTHOR)<i> carlotta.ferrando@unige.it</i><br /><searchLink fieldCode="AR" term="%22Borghini%2C+G%2E%22">Borghini, G.</searchLink><relatesTo>3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Sani%2C+C%2E%22">Sani, C.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Genske%2C+F%2E%22">Genske, F.</searchLink><relatesTo>4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Ligi%2C+M%2E%22">Ligi, M.</searchLink><relatesTo>5</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Stracke%2C+A%2E%22">Stracke, A.</searchLink><relatesTo>4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Sanfilippo%2C+A%2E%22">Sanfilippo, A.</searchLink><relatesTo>1,6</relatesTo> (AUTHOR) – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Chemical+Geology%22">Chemical Geology</searchLink>. Jan2024, Vol. 644, pN.PAG-N.PAG. 1p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Melt+crystallization%22">Melt crystallization</searchLink><br /><searchLink fieldCode="DE" term="%22Mid-ocean+ridges%22">Mid-ocean ridges</searchLink><br /><searchLink fieldCode="DE" term="%22Lithosphere%22">Lithosphere</searchLink><br /><searchLink fieldCode="DE" term="%22Isotopic+signatures%22">Isotopic signatures</searchLink><br /><searchLink fieldCode="DE" term="%22Pyroxenite%22">Pyroxenite</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Partial melting of mantle peridotite from which considerable amounts of melt have been extracted during prior melting episodes generates melts characterized by low incompatible element contents and very low ratios of highly to moderately incompatible elements, so-called 'ultra-depleted' melts. Reaction of peridotite with percolating ultra-depleted melts has been inferred from petrological-geochemical studies of abyssal peridotites and ophiolites. But so far, direct evidence for the existence of ultra-depleted melts, only comes from rare melt inclusions. Here, we show that a pyroxenite layer within abyssal peridotite from the Mid Atlantic Ridge (8°N, Doldrums Fracture Zone) formed by crystallization of a segregated melt that is highly depleted in incompatible elements, at >27 km-depth beneath the ridge axis (at T ∼ 1250 °C), and with little or no modification by interaction with the host harzburgite. During exhumation, the pyroxenite experienced decompression and partial re-equilibration under plagioclase-facies conditions (∼1060 °C and ∼ 15 km depth). The high Hf isotope ratio (εHf = 40.3) of the pyroxenite clinopyroxene is inherited from a melt sourced from an ultra-depleted peridotite that evolved with high Lu/Hf. The associated MORB-like Nd isotope ratios (εNd = 10.6), however, imply a long-term evolution of the source peridotite with composition moderately depleted in incompatible elements (rather low Sm/Nd). These compositions are different from the host harzburgite, but typical for peridotites that have melted and partially reacted with migrating melts in ancient times. Hence, the pyroxenite investigated here is a partial melt from an ultra-depleted peridotite that has become re-enriched in incompatible elements and clinopyroxene. This melt crystallized in the oceanic lithosphere, and partially re-equilibrated at low pressure during exhumation. Overall, our results show that renewed melting of ultra-depleted peridotites with a complex history of prior melting and melt-rock reaction occurs, and that such melts migrate through the sub-ridge mantle, and can thus contribute to mid ocean ridge magmatism, although to a still unknown extent. • Abyssal pyroxenite hold the isotopic signature of the parental melt mantle source. • Doldrums pyroxenite records melting of ancient ultra-depleted, refertilized mantle. • Refertilization enables melting of otherwise ancient refractory mantle. • Segregation shortly after melt generation preserves trace of ultra-depleted melts. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Chemical Geology is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.) |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1016/j.chemgeo.2023.121840 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 1 StartPage: N.PAG Subjects: – SubjectFull: Melt crystallization Type: general – SubjectFull: Mid-ocean ridges Type: general – SubjectFull: Lithosphere Type: general – SubjectFull: Isotopic signatures Type: general – SubjectFull: Pyroxenite Type: general Titles: – TitleFull: Deep segregation and crystallization of ultra-depleted melts in the sub-ridge mantle. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Ferrando, C. – PersonEntity: Name: NameFull: Borghini, G. – PersonEntity: Name: NameFull: Sani, C. – PersonEntity: Name: NameFull: Genske, F. – PersonEntity: Name: NameFull: Ligi, M. – PersonEntity: Name: NameFull: Stracke, A. – PersonEntity: Name: NameFull: Sanfilippo, A. IsPartOfRelationships: – BibEntity: Dates: – D: 20 M: 01 Text: Jan2024 Type: published Y: 2024 Identifiers: – Type: issn-print Value: 00092541 Numbering: – Type: volume Value: 644 Titles: – TitleFull: Chemical Geology Type: main |
| ResultId | 1 |
