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Metamorphic transformation rate over large spatial and temporal scales constrained by geophysical data and coupled modelling / Gyorgy Hetényl in Journal of metamorphic geology, vol 39 n° 9 (December 2021)  

Public [article]  inJournal of metamorphic geology > vol 39 n° 9 (December 2021) . - pp 1131 - 1143 Titre : Metamorphic transformation rate over large spatial and temporal scales constrained by geophysical data and coupled modelling Type de document : Article/Communication Auteurs : Gyorgy Hetényl, Auteur ; Kristel Chanard , Auteur ; Lukas P. Baumgartner, Auteur ; Frédéric Herman, Auteur Année de publication : 2021 Projets : 3-projet - voir note / Article en page(s) : pp 1131 - 1143 Note générale : bibliographie We are grateful to the Swiss National Science Foundation for funding project OROG3NY through grant PP00P2_157627. Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] anomalie de pesanteur [Termes IGN] croute terrestre [Termes IGN] géodynamique [Termes IGN] Inde [Termes IGN] modèle numérique [Termes IGN] roche métamorphique Résumé : (auteur) Metamorphic transformation rates are classically determined on decimetre-scale field samples and from laboratory experiments at smaller scales. Here we present a geophysical approach based on field data and joint geophysical–petrological modelling to quantify the average rate of metamorphic transformations at the 10–100-kilometre and million-year scales. The model simulates the eclogitization of Indian lower crust as it penetrates beneath southern Tibet. Metamorphic transformation of the lower crust is tracked by its densification, the effect of which is then compared to observed gravity anomalies. From the modelling we find that the Indian lower crust's overall densification requires a partially hydrated initial composition. Moreover, the modelled evolution of this densification compared to what is predicted by pressure–temperature–density grids is consistent with delayed, far-from-equilibrium metamorphism. The Indian lower crust descends underneath the Himalaya until beneath southern Tibet in a thermodynamically metastable state until the first dehydration reactions are reached. This observation is used to determine the average rate of metastable rock transformation to an eclogite facies assemblage, constrained at between ~6 × 10−9 and 5 × 10−7 g/cm2/year, and reaction affinity at 0.8–1.6 kJ/mol oxygen. Compared to field and laboratory data, this range of results matches the effective rates typically associated with regional metamorphism. This fit and correlation across the scales legitimates the use of transformation rates determined at small scales in large-scale geodynamic studies. Numéro de notice : A2021-789 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Autre URL associée : vers HAL Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/jmg.12604 En ligne : https://doi.org/10.1111/jmg.12604 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98988 [article]