Metasomatic textural changes in hypabyssal transitional kimberlites: inferences for pyroclastic kimberlites.
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| Title: | Metasomatic textural changes in hypabyssal transitional kimberlites: inferences for pyroclastic kimberlites. |
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| Authors: | Kopylova, Maya G.1 (AUTHOR) mkopylov@eos.ubc.ca, Sismondo, Clara1 (AUTHOR), Gaudet, Matthew1 (AUTHOR) |
| Source: | Mineralogy & Petrology. Dec2025, Vol. 119 Issue 4, p1101-1118. 18p. |
| Subjects: | Metasomatism, Kimberlite, Phase transitions, Inclusions in igneous rocks, Mineralogy, Volcanic ash, tuff, etc., Geological surveys, Pseudomorphs |
| Abstract: | One of the most distinctive features of Kimberley-type pyroclastic kimberlites (KPK) is the occurrence of elliptical serpentinized melt-bearing pyroclasts (also known as pelletal lapilli) with microlitic clinopyroxene rims. We propose a new model for their formation based on petrographic observations in hypabyssal transitional kimberlites (HKt) from Renard 65 and 5034 pipes (Canada). We show that subsolidus metasomatic reactions between the kimberlite and entrained crustal silicate xenoliths create serpentine segregations and pseudoclastic textures around the xenoliths. A preferential serpentinisation of the fine HKt groundmass between coarser olivine grains makes oval "pseudoclasts" resembling pelletal lapilli. Radial outward-oriented microlites of fibrous clinopyroxene form reactive coronas on the xenoliths and on the serpentinized olivine. Petrographic evidence for the metasomatic development of the pseudoclastic texture matches the Perple_X phase equilibria calculations that model the serpentinization in the subsolidus, driven by Si ingress across the xenolith–kimberlite contacts. The serpentine-producing reactions constrained by the observed mineralogy expand the volume by 3–44%. The pseudoclastic texture in HKt forms when silicate xenoliths are abundant, adding enough Si to ensure voluminous serpentine and clinopyroxene production and decomposition of primary kimberlitic calcite. The model of metasomatic development of pseudoclasts may be relevant to KPKs as i) there is a gradual transition from HKt to KPK textures correlated with the silicate xenolith modes, and ii) KPK textures are exclusively associated with pipes in competent crystalline silicate rocks. We propose that Kimberley-type pyroclastic kimberlites include assemblages formed in several intrusive and volcanic emplacement episodes, and some pelletal lapilli in KPK may be recycled from the previous magmatic HKt phases. [ABSTRACT FROM AUTHOR] |
| Copyright of Mineralogy & Petrology is the property of Springer Nature 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.) | |
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| Items | – Name: Title Label: Title Group: Ti Data: Metasomatic textural changes in hypabyssal transitional kimberlites: inferences for pyroclastic kimberlites. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Kopylova%2C+Maya+G%2E%22">Kopylova, Maya G.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> mkopylov@eos.ubc.ca</i><br /><searchLink fieldCode="AR" term="%22Sismondo%2C+Clara%22">Sismondo, Clara</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Gaudet%2C+Matthew%22">Gaudet, Matthew</searchLink><relatesTo>1</relatesTo> (AUTHOR) – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Mineralogy+%26+Petrology%22">Mineralogy & Petrology</searchLink>. Dec2025, Vol. 119 Issue 4, p1101-1118. 18p. – Name: Subject Label: Subjects Group: Su Data: <searchLink fieldCode="DE" term="%22Metasomatism%22">Metasomatism</searchLink><br /><searchLink fieldCode="DE" term="%22Kimberlite%22">Kimberlite</searchLink><br /><searchLink fieldCode="DE" term="%22Phase+transitions%22">Phase transitions</searchLink><br /><searchLink fieldCode="DE" term="%22Inclusions+in+igneous+rocks%22">Inclusions in igneous rocks</searchLink><br /><searchLink fieldCode="DE" term="%22Mineralogy%22">Mineralogy</searchLink><br /><searchLink fieldCode="DE" term="%22Volcanic+ash%2C+tuff%2C+etc%2E%22">Volcanic ash, tuff, etc.</searchLink><br /><searchLink fieldCode="DE" term="%22Geological+surveys%22">Geological surveys</searchLink><br /><searchLink fieldCode="DE" term="%22Pseudomorphs%22">Pseudomorphs</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: One of the most distinctive features of Kimberley-type pyroclastic kimberlites (KPK) is the occurrence of elliptical serpentinized melt-bearing pyroclasts (also known as pelletal lapilli) with microlitic clinopyroxene rims. We propose a new model for their formation based on petrographic observations in hypabyssal transitional kimberlites (HKt) from Renard 65 and 5034 pipes (Canada). We show that subsolidus metasomatic reactions between the kimberlite and entrained crustal silicate xenoliths create serpentine segregations and pseudoclastic textures around the xenoliths. A preferential serpentinisation of the fine HKt groundmass between coarser olivine grains makes oval "pseudoclasts" resembling pelletal lapilli. Radial outward-oriented microlites of fibrous clinopyroxene form reactive coronas on the xenoliths and on the serpentinized olivine. Petrographic evidence for the metasomatic development of the pseudoclastic texture matches the Perple_X phase equilibria calculations that model the serpentinization in the subsolidus, driven by Si ingress across the xenolith–kimberlite contacts. The serpentine-producing reactions constrained by the observed mineralogy expand the volume by 3–44%. The pseudoclastic texture in HKt forms when silicate xenoliths are abundant, adding enough Si to ensure voluminous serpentine and clinopyroxene production and decomposition of primary kimberlitic calcite. The model of metasomatic development of pseudoclasts may be relevant to KPKs as i) there is a gradual transition from HKt to KPK textures correlated with the silicate xenolith modes, and ii) KPK textures are exclusively associated with pipes in competent crystalline silicate rocks. We propose that Kimberley-type pyroclastic kimberlites include assemblages formed in several intrusive and volcanic emplacement episodes, and some pelletal lapilli in KPK may be recycled from the previous magmatic HKt phases. [ABSTRACT FROM AUTHOR] – Name: AbstractSuppliedCopyright Label: Group: Ab Data: <i>Copyright of Mineralogy & Petrology is the property of Springer Nature 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: 10.1007/s00710-025-00893-6 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 18 StartPage: 1101 Subjects: – SubjectFull: Metasomatism Type: general – SubjectFull: Kimberlite Type: general – SubjectFull: Phase transitions Type: general – SubjectFull: Inclusions in igneous rocks Type: general – SubjectFull: Mineralogy Type: general – SubjectFull: Volcanic ash, tuff, etc. Type: general – SubjectFull: Geological surveys Type: general – SubjectFull: Pseudomorphs Type: general Titles: – TitleFull: Metasomatic textural changes in hypabyssal transitional kimberlites: inferences for pyroclastic kimberlites. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Kopylova, Maya G. – PersonEntity: Name: NameFull: Sismondo, Clara – PersonEntity: Name: NameFull: Gaudet, Matthew IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 12 Text: Dec2025 Type: published Y: 2025 Identifiers: – Type: issn-print Value: 09300708 Numbering: – Type: volume Value: 119 – Type: issue Value: 4 Titles: – TitleFull: Mineralogy & Petrology Type: main |
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