The Th/La and Sm/La conundrum of the Tethyan realm lamproites
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| Title: | The Th/La and Sm/La conundrum of the Tethyan realm lamproites |
|---|---|
| Authors: | Tommasini, Simone1 toms@unifi.it, Avanzinelli, Riccardo1, Conticelli, Sandro1,2 |
| Source: | Earth & Planetary Science Letters. Jan2011, Vol. 301 Issue 3/4, p469-478. 10p. |
| Subjects: | Lamproite, Oligocene stratigraphic geology, Pleistocene stratigraphic geology, Geodynamics, Metasomatism, Trace elements, Tethys (Paleogeography), Isotopes, Earth's mantle, Earth (Planet) |
| Abstract: | Abstract: The Oligocene–Pleistocene Tethyan Realm Lamproites, from the Mediterranean to Himalayas, have a clear subduction-related signature and represent one of the most exotic and rare ultrapotassic mantle-derived magmas. They share the major element and mineralogical characteristics of the lamproite clan rocks, but clearly define a distinct subgroup with respect to within-plate lamproites on the basis of a number of key trace element ratios and radiogenic isotopes. The most striking characteristic of the Tethyan Realm Lamproites is the positive correlation between Th/La (up to >1.5) and Sm/La (up to >0.3), which is opposite to what observed in subduction-related magmas worldwide and cannot be reconciled with typical slab recycling processes. The geochemical conundrum of the Tethyan Realm Lamproites requires a component with high Sm/La and Th/La (hence named SALATHO), in addition to a normal K2O–rich sediment melt component (with low Th/La and Sm/La). The Pb isotope composition of the Tethyan Realm Lamproites also displays a mixing array from a normal sediment melt component to a high 208Pb/206Pb and low 206Pb/204Pb end-member that can be reconciled with the SALATHO component. This end-member requires a history of high time-integrated κ (232Th/238U) and low time-integrated μ (238U/204Pb) and ought to be older than some hundreds of million years. We propose a multi-stage process for the formation of the mantle sources of the Tethyan Realm Lamproites related to the tectonic mélange domains (i.e. chaotic mixture of depleted peridotite, basalt, and sediment) accreted to the Eurasia plate during the collisional events of the northward drifting continental slivers from Gondwana. In a first stage, the mélange domains experienced high P and low T metamorphism with segregation and stabilisation of lawsonite and zoisite/epidote veins, which potentially match the geochemical characteristics required by the SALATHO component. Successively, the subduction of the Neotethys and Alpine Tethys oceanic plates produced normal K2O-rich sediment melts that migrated through the mantle wedge and metasomatised the depleted lithospheric mantle blocks within the chaotic mélange, forming a clinopyroxene–phlogopite vein network. Eventually, the Tertiary orogenic belt collapses triggered the onset of low-degree melting of the low-solidus fractions within the mélange domains, producing lamproitic magmas. [Copyright &y& Elsevier] |
| Copyright of Earth & Planetary Science Letters 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: 57164720 AccessLevel: 6 PubType: Academic Journal PubTypeId: academicJournal PreciseRelevancyScore: 0 |
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| Items | – Name: Title Label: Title Group: Ti Data: The Th/La and Sm/La conundrum of the Tethyan realm lamproites – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Tommasini%2C+Simone%22">Tommasini, Simone</searchLink><relatesTo>1</relatesTo><i> toms@unifi.it</i><br /><searchLink fieldCode="AR" term="%22Avanzinelli%2C+Riccardo%22">Avanzinelli, Riccardo</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Conticelli%2C+Sandro%22">Conticelli, Sandro</searchLink><relatesTo>1,2</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Earth+%26+Planetary+Science+Letters%22">Earth & Planetary Science Letters</searchLink>. Jan2011, Vol. 301 Issue 3/4, p469-478. 10p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Lamproite%22">Lamproite</searchLink><br /><searchLink fieldCode="DE" term="%22Oligocene+stratigraphic+geology%22">Oligocene stratigraphic geology</searchLink><br /><searchLink fieldCode="DE" term="%22Pleistocene+stratigraphic+geology%22">Pleistocene stratigraphic geology</searchLink><br /><searchLink fieldCode="DE" term="%22Geodynamics%22">Geodynamics</searchLink><br /><searchLink fieldCode="DE" term="%22Metasomatism%22">Metasomatism</searchLink><br /><searchLink fieldCode="DE" term="%22Trace+elements%22">Trace elements</searchLink><br /><searchLink fieldCode="DE" term="%22Tethys+%28Paleogeography%29%22">Tethys (Paleogeography)</searchLink><br /><searchLink fieldCode="DE" term="%22Isotopes%22">Isotopes</searchLink><br /><searchLink fieldCode="DE" term="%22Earth's+mantle%22">Earth's mantle</searchLink><br /><searchLink fieldCode="DE" term="%22Earth+%28Planet%29%22">Earth (Planet)</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Abstract: The Oligocene–Pleistocene Tethyan Realm Lamproites, from the Mediterranean to Himalayas, have a clear subduction-related signature and represent one of the most exotic and rare ultrapotassic mantle-derived magmas. They share the major element and mineralogical characteristics of the lamproite clan rocks, but clearly define a distinct subgroup with respect to within-plate lamproites on the basis of a number of key trace element ratios and radiogenic isotopes. The most striking characteristic of the Tethyan Realm Lamproites is the positive correlation between Th/La (up to >1.5) and Sm/La (up to >0.3), which is opposite to what observed in subduction-related magmas worldwide and cannot be reconciled with typical slab recycling processes. The geochemical conundrum of the Tethyan Realm Lamproites requires a component with high Sm/La and Th/La (hence named SALATHO), in addition to a normal K2O–rich sediment melt component (with low Th/La and Sm/La). The Pb isotope composition of the Tethyan Realm Lamproites also displays a mixing array from a normal sediment melt component to a high 208Pb/206Pb and low 206Pb/204Pb end-member that can be reconciled with the SALATHO component. This end-member requires a history of high time-integrated κ (232Th/238U) and low time-integrated μ (238U/204Pb) and ought to be older than some hundreds of million years. We propose a multi-stage process for the formation of the mantle sources of the Tethyan Realm Lamproites related to the tectonic mélange domains (i.e. chaotic mixture of depleted peridotite, basalt, and sediment) accreted to the Eurasia plate during the collisional events of the northward drifting continental slivers from Gondwana. In a first stage, the mélange domains experienced high P and low T metamorphism with segregation and stabilisation of lawsonite and zoisite/epidote veins, which potentially match the geochemical characteristics required by the SALATHO component. Successively, the subduction of the Neotethys and Alpine Tethys oceanic plates produced normal K2O-rich sediment melts that migrated through the mantle wedge and metasomatised the depleted lithospheric mantle blocks within the chaotic mélange, forming a clinopyroxene–phlogopite vein network. Eventually, the Tertiary orogenic belt collapses triggered the onset of low-degree melting of the low-solidus fractions within the mélange domains, producing lamproitic magmas. [Copyright &y& Elsevier] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Earth & Planetary Science Letters 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.epsl.2010.11.023 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 10 StartPage: 469 Subjects: – SubjectFull: Lamproite Type: general – SubjectFull: Oligocene stratigraphic geology Type: general – SubjectFull: Pleistocene stratigraphic geology Type: general – SubjectFull: Geodynamics Type: general – SubjectFull: Metasomatism Type: general – SubjectFull: Trace elements Type: general – SubjectFull: Tethys (Paleogeography) Type: general – SubjectFull: Isotopes Type: general – SubjectFull: Earth's mantle Type: general – SubjectFull: Earth (Planet) Type: general Titles: – TitleFull: The Th/La and Sm/La conundrum of the Tethyan realm lamproites Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Tommasini, Simone – PersonEntity: Name: NameFull: Avanzinelli, Riccardo – PersonEntity: Name: NameFull: Conticelli, Sandro IsPartOfRelationships: – BibEntity: Dates: – D: 15 M: 01 Text: Jan2011 Type: published Y: 2011 Identifiers: – Type: issn-print Value: 0012821X Numbering: – Type: volume Value: 301 – Type: issue Value: 3/4 Titles: – TitleFull: Earth & Planetary Science Letters Type: main |
| ResultId | 1 |
