Benito Ábalos, Pablo Puelles, José Ignacio Gil Ibarguchi
{"title":"Polyphase tectonic reworking of serpentinites and chlorite-tremolite-talc rocks (SW Spain) from the subduction forearc to intracontinental emplacement","authors":"Benito Ábalos, Pablo Puelles, José Ignacio Gil Ibarguchi","doi":"10.1111/jmg.12704","DOIUrl":null,"url":null,"abstract":"<p>The petrostructural and geochronological study of a poorly known ultramafic unit from SW Spain (Badajoz–Córdoba belt) combined with previous structural data permits disclosure of a history of metasomatism, tectono-metamorphism, reworking and isotopic resetting related to a poly-orogenic evolution in different geodynamic scenarios. The heterogeneous ultramafic unit studied contains antigorite-serpentinites and metasomatized ultramafic rocks (chlorite-talc schists, tremolite-talc-chlorite rocks and magnesio-hornblende-chlorite rocks). Mantle-wedge serpentinization was followed by Si and Al pre- to syn-metamorphic/tectonic metasomatism in a subduction realm. Petrofabrics of selected lithologies reveal variable syn-metamorphic crystal-plastic deformation and recrystallization (assisted by other mechanisms) under relative high pressure, concomitant with the conditions recorded by neighbouring tectonic units that were later intruded by Ordovician granites. The resultant ensemble was reworked and isotopically reset much later in an intracontinental ductile shear zone. Syn- to late-tectonic apatite from chlorite-talc schists provides an anchored Tera–Wassenburg isochron radiometric age of 342.8 ± 12.2 Ma that provides evidence for the decoupling between isotopic systems and microstructures. The results are discussed from a twofold perspective: with regard to the likely tectonic context of this ophiolite (the current analogue of the Mariana forearc) and with regard to regional geological implications.</p>","PeriodicalId":16472,"journal":{"name":"Journal of Metamorphic Geology","volume":null,"pages":null},"PeriodicalIF":3.5000,"publicationDate":"2022-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jmg.12704","citationCount":"1","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Metamorphic Geology","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/jmg.12704","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOLOGY","Score":null,"Total":0}
引用次数: 1
Abstract
The petrostructural and geochronological study of a poorly known ultramafic unit from SW Spain (Badajoz–Córdoba belt) combined with previous structural data permits disclosure of a history of metasomatism, tectono-metamorphism, reworking and isotopic resetting related to a poly-orogenic evolution in different geodynamic scenarios. The heterogeneous ultramafic unit studied contains antigorite-serpentinites and metasomatized ultramafic rocks (chlorite-talc schists, tremolite-talc-chlorite rocks and magnesio-hornblende-chlorite rocks). Mantle-wedge serpentinization was followed by Si and Al pre- to syn-metamorphic/tectonic metasomatism in a subduction realm. Petrofabrics of selected lithologies reveal variable syn-metamorphic crystal-plastic deformation and recrystallization (assisted by other mechanisms) under relative high pressure, concomitant with the conditions recorded by neighbouring tectonic units that were later intruded by Ordovician granites. The resultant ensemble was reworked and isotopically reset much later in an intracontinental ductile shear zone. Syn- to late-tectonic apatite from chlorite-talc schists provides an anchored Tera–Wassenburg isochron radiometric age of 342.8 ± 12.2 Ma that provides evidence for the decoupling between isotopic systems and microstructures. The results are discussed from a twofold perspective: with regard to the likely tectonic context of this ophiolite (the current analogue of the Mariana forearc) and with regard to regional geological implications.
期刊介绍:
The journal, which is published nine times a year, encompasses the entire range of metamorphic studies, from the scale of the individual crystal to that of lithospheric plates, including regional studies of metamorphic terranes, modelling of metamorphic processes, microstructural and deformation studies in relation to metamorphism, geochronology and geochemistry in metamorphic systems, the experimental study of metamorphic reactions, properties of metamorphic minerals and rocks and the economic aspects of metamorphic terranes.