The chromitites of the Neoproterozoic Bou Azzer ophiolite (central Anti-Atlas, Morocco) revisited
The Neoproterozoic Bou Azzer ophiolite in the Moroccan Anti-Atlas Panafrican belt hosts numerous chromitite orebodies within the peridotite section of the oceanic mantle. The chromitites are strongly affected by serpentinization and metamorphism, although they still preserve igneous relicts amenable...
| Autores: | , , , , , , , , |
|---|---|
| Tipo de documento: | artigo |
| Estado: | Versão publicada |
| Data de publicação: | 2021 |
| País: | España |
| Recursos: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositório: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/275868 |
| Acesso em linha: | http://hdl.handle.net/10261/275868 |
| Access Level: | Acceso aberto |
| Palavra-chave: | Ophiolitic chromitites Unusual (“exotic”) mineral assemblages Trace elements Platinum group minerals (PGM) Subduction-initiation Fore-arc basalts (FAB |
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The chromitites of the Neoproterozoic Bou Azzer ophiolite (central Anti-Atlas, Morocco) revisited |
| title |
The chromitites of the Neoproterozoic Bou Azzer ophiolite (central Anti-Atlas, Morocco) revisited |
| spellingShingle |
The chromitites of the Neoproterozoic Bou Azzer ophiolite (central Anti-Atlas, Morocco) revisited Pujol-Solà, Núria Ophiolitic chromitites Unusual (“exotic”) mineral assemblages Trace elements Platinum group minerals (PGM) Subduction-initiation Fore-arc basalts (FAB |
| title_short |
The chromitites of the Neoproterozoic Bou Azzer ophiolite (central Anti-Atlas, Morocco) revisited |
| title_full |
The chromitites of the Neoproterozoic Bou Azzer ophiolite (central Anti-Atlas, Morocco) revisited |
| title_fullStr |
The chromitites of the Neoproterozoic Bou Azzer ophiolite (central Anti-Atlas, Morocco) revisited |
| title_full_unstemmed |
The chromitites of the Neoproterozoic Bou Azzer ophiolite (central Anti-Atlas, Morocco) revisited |
| title_sort |
The chromitites of the Neoproterozoic Bou Azzer ophiolite (central Anti-Atlas, Morocco) revisited |
| dc.creator.none.fl_str_mv |
Pujol-Solà, Núria Domínguez-Carretero, D. Proenza, Joaquín A. Haissen, Faouziya Ikenne, M. González-Jiménez, José María Colas, V. Maacha, Lhou Garcia Casco, Antonio |
| author |
Pujol-Solà, Núria |
| author_facet |
Pujol-Solà, Núria Domínguez-Carretero, D. Proenza, Joaquín A. Haissen, Faouziya Ikenne, M. González-Jiménez, José María Colas, V. Maacha, Lhou Garcia Casco, Antonio |
| author_role |
author |
| author2 |
Domínguez-Carretero, D. Proenza, Joaquín A. Haissen, Faouziya Ikenne, M. González-Jiménez, José María Colas, V. Maacha, Lhou Garcia Casco, Antonio |
| author2_role |
author author author author author author author author |
| dc.contributor.none.fl_str_mv |
Ministerio de Educación y Ciencia (España) Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72] |
| dc.subject.none.fl_str_mv |
Ophiolitic chromitites Unusual (“exotic”) mineral assemblages Trace elements Platinum group minerals (PGM) Subduction-initiation Fore-arc basalts (FAB |
| topic |
Ophiolitic chromitites Unusual (“exotic”) mineral assemblages Trace elements Platinum group minerals (PGM) Subduction-initiation Fore-arc basalts (FAB |
| description |
The Neoproterozoic Bou Azzer ophiolite in the Moroccan Anti-Atlas Panafrican belt hosts numerous chromitite orebodies within the peridotite section of the oceanic mantle. The chromitites are strongly affected by serpentinization and metamorphism, although they still preserve igneous relicts amenable for petrogenetic interpretation. The major, minor and trace element composition of unaltered chromite cores reveal two compositional groups: intermediate-Cr (Cr# = 0.60 – 0.74) and high-Cr (Cr# = 0.79 – 0.84) and estimates of parental melt compositions suggest crystallization from pulses of fore-arc basalts (FAB) and boninitic melts, respectively, that infiltrated the oceanic supra-subduction zone (SSZ) mantle. A platinum group elements (PGE) mineralization dominated by Ir-Ru-Os is recognized in the chromitites, which has its mineralogical expression in abundant inclusions of Os-Ir alloys and coexisting magmatic laurite (RuS) and their products of metamorphic alteration. Unusual mineral phases in chromite, not previously reported in this ophiolite, include super-reduced and/or nominally ultra-high pressure minerals moissanite (SiC), native Cu and silicates (oriented clinopyroxene lamellae), but “exotic” zircon and diaspore have also been identified. We interpret that clinopyroxene lamellae have a magmatic origin, whereas super-reduced phases originated during serpentinization processes and diaspore is linked to late circulation of low-silica fluids related to rodingitization. Zircon grains, on the other hand, with apatite and serpentine inclusions, could either have formed after the interaction of chromitite with mantle-derived melts or could represent subducted detrital sediments later incorporated into the chromitites. We offer a comparison of the Bou Azzer chromitites with other Precambrian ophiolitic chromitites worldwide, which are rather scarce in the geological record. The studied chromitites are very similar to the Neoproterozoic chromitites reported in the Arabian-Nubian shield, which are also related to the Panafrican orogeny. Thus, we conclude that the Bou Azzer chromitites formed in a subduction-initiation geodynamic setting with two-stages of evolution, with formation of FAB-derived intermediate-Cr chromitites in the early stage and formation of boninite-derived high-Cr chromitites in the late stage. |
| publishDate |
2021 |
| dc.date.none.fl_str_mv |
2021 2022 2022 2022 |
| dc.type.none.fl_str_mv |
info:eu-repo/semantics/article http://purl.org/coar/resource_type/c_6501 Publisher's version info:eu-repo/semantics/publishedVersion |
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article |
| status_str |
publishedVersion |
| dc.identifier.none.fl_str_mv |
http://hdl.handle.net/10261/275868 |
| url |
http://hdl.handle.net/10261/275868 |
| dc.language.none.fl_str_mv |
Inglés |
| language_invalid_str_mv |
Inglés |
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info:eu-repo/semantics/openAccess |
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openAccess |
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Elsevier BV |
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Elsevier BV |
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reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC instname:Consejo Superior de Investigaciones Científicas (CSIC) |
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Consejo Superior de Investigaciones Científicas (CSIC) |
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DIGITAL.CSIC. Repositorio Institucional del CSIC |
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DIGITAL.CSIC. Repositorio Institucional del CSIC |
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The chromitites of the Neoproterozoic Bou Azzer ophiolite (central Anti-Atlas, Morocco) revisitedPujol-Solà, NúriaDomínguez-Carretero, D.Proenza, Joaquín A.Haissen, FaouziyaIkenne, M.González-Jiménez, José MaríaColas, V.Maacha, LhouGarcia Casco, AntonioOphiolitic chromititesUnusual (“exotic”) mineral assemblagesTrace elementsPlatinum group minerals (PGM)Subduction-initiationFore-arc basalts (FABThe Neoproterozoic Bou Azzer ophiolite in the Moroccan Anti-Atlas Panafrican belt hosts numerous chromitite orebodies within the peridotite section of the oceanic mantle. The chromitites are strongly affected by serpentinization and metamorphism, although they still preserve igneous relicts amenable for petrogenetic interpretation. The major, minor and trace element composition of unaltered chromite cores reveal two compositional groups: intermediate-Cr (Cr# = 0.60 – 0.74) and high-Cr (Cr# = 0.79 – 0.84) and estimates of parental melt compositions suggest crystallization from pulses of fore-arc basalts (FAB) and boninitic melts, respectively, that infiltrated the oceanic supra-subduction zone (SSZ) mantle. A platinum group elements (PGE) mineralization dominated by Ir-Ru-Os is recognized in the chromitites, which has its mineralogical expression in abundant inclusions of Os-Ir alloys and coexisting magmatic laurite (RuS) and their products of metamorphic alteration. Unusual mineral phases in chromite, not previously reported in this ophiolite, include super-reduced and/or nominally ultra-high pressure minerals moissanite (SiC), native Cu and silicates (oriented clinopyroxene lamellae), but “exotic” zircon and diaspore have also been identified. We interpret that clinopyroxene lamellae have a magmatic origin, whereas super-reduced phases originated during serpentinization processes and diaspore is linked to late circulation of low-silica fluids related to rodingitization. Zircon grains, on the other hand, with apatite and serpentine inclusions, could either have formed after the interaction of chromitite with mantle-derived melts or could represent subducted detrital sediments later incorporated into the chromitites. We offer a comparison of the Bou Azzer chromitites with other Precambrian ophiolitic chromitites worldwide, which are rather scarce in the geological record. The studied chromitites are very similar to the Neoproterozoic chromitites reported in the Arabian-Nubian shield, which are also related to the Panafrican orogeny. Thus, we conclude that the Bou Azzer chromitites formed in a subduction-initiation geodynamic setting with two-stages of evolution, with formation of FAB-derived intermediate-Cr chromitites in the early stage and formation of boninite-derived high-Cr chromitites in the late stage.This research was financially supported by the Fondo Europeo de Desarrollo Regional (FEDER) Funds, the Spanish Projects CGL2015–65824, RTI2018-099157-A-I00, PID2019-105625RB-C21,and A.RNM.186.UGR18. Additional funding was provided by a FPU-PhD grant to NPS by the “Ministerio de Educación” of the Spanish Government, the Ramón y Cajal Fellowship RYC-2015-17596 to JMGJ, and the Mexican research programs CONACYT-Ciencia B ́asica A1-S-14574 and UNAM-PAPIIT grant IA-101419 to VC. The help extended by MANAGEM mining company is greatly acknowledged. We are also indebted to Thomas Aiglsperger, Lidia Butjosa and Cristina Villanova-de-Benavent for their participation during fieldwork, to Aleu Andreazini for his support during sample preparation, to Xavier Llovet from the Centres Científics i Tecnol`ogics of the Universitat of Barcelona (CCiTUB) for his careful help with EMPA, and to Carlos Ortega-Obreg ́on from the Laboratorio de Estudios Isot ́opicos of the Centro de Geociencias (UNAM, Mexico) for his help with the LA-ICP-MS analyses on chromite. Ben-Xun Su, one anonymous reviewer, and editors Ibrahim Uysal and Franco Pirajno are deeply acknowledged for their constructive criticism that has helped to improve the manuscript.Elsevier BVMinisterio de Educación y Ciencia (España)Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]2022202220212022info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501Publisher's versioninfo:eu-repo/semantics/publishedVersionhttp://hdl.handle.net/10261/275868reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)Inglés#PLACEHOLDER_PARENT_METADATA_VALUE##PLACEHOLDER_PARENT_METADATA_VALUE##PLACEHOLDER_PARENT_METADATA_VALUE#info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2017-2020/RTI2018-099157-A-I00info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2017-2020/PID2019-105625RB-C21info:eu-repo/grantAgreement/AEI/Plan Estatal de Investigación Científica y Técnica y de Innovación 2017-2020/PID2019-105625RB-C22http://dx.doi.org/10.1016/j.oregeorev.2021.104166Síinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/2758682026-05-22T06:33:51Z |
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15.812455 |