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Melting and Metasomatism/Refertilisation Processes in the Patagonian Sub-Continental Lithospheric Mantle

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Melting and Metasomatism/Refertilisation Processes in the Patagonian Sub-Continental Lithospheric Mantle Melting and metasomatism/refertilisation processes in the Patagonian sub-continental lithospheric mantle: A review Massimiliano Melchiorre, Barbara Faccini, Michel Grégoire, Mathieu Benoit, Federico Casetta, Massimo Coltorti To cite this version: Massimiliano Melchiorre, Barbara Faccini, Michel Grégoire, Mathieu Benoit, Federico Casetta, et al.. Melting and metasomatism/refertilisation processes in the Patagonian sub-continental lithospheric mantle: A review. Lithos, Elsevier, 2020, 354-355, pp.105324. 10.1016/j.lithos.2019.105324. hal- 03267036 HAL Id: hal-03267036 https://hal.archives-ouvertes.fr/hal-03267036 Submitted on 22 Jun 2021 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/337816314 Melting and metasomatism/refertilisation processes in the Patagonian sub- continental lithospheric mantle: A review Article in Lithos · December 2019 DOI: 10.1016/j.lithos.2019.105324 CITATIONS READS 0 22 6 authors, including: Massimiliano Melchiorre Barbara Faccini Spanish National Research Council University of Ferrara 42 PUBLICATIONS 90 CITATIONS 88 PUBLICATIONS 644 CITATIONS SEE PROFILE SEE PROFILE Michel Grégoire Mathieu Benoit French National Centre for Scientific Research Paul Sabatier University - Toulouse III 220 PUBLICATIONS 3,123 CITATIONS 130 PUBLICATIONS 1,906 CITATIONS SEE PROFILE SEE PROFILE Some of the authors of this publication are also working on these related projects: Origin and evolution of ultra-refractory peridotites in oceanic large igneous provinces View project Geochemistry of noble gases and CO2 in mantle xenoliths from Europe and circum-Mediterranean area View project All content following this page was uploaded by Barbara Faccini on 13 December 2019. The user has requested enhancement of the downloaded file. Journal Pre-proof Melting and metasomatism/refertilisation processes in the Patagonian sub-continental lithospheric mantle: A review Massimiliano Melchiorre, Barbara Faccini, Michel Gregoire, Mathieu Benoit, Federico Casetta, Massimo Coltorti PII: S0024-4937(19)30484-0 DOI: https://doi.org/10.1016/j.lithos.2019.105324 Reference: LITHOS 105324 To appear in: LITHOS Received date: 10 April 2019 Revised date: 26 November 2019 Accepted date: 4 December 2019 Please cite this article as: M. Melchiorre, B. Faccini, M. Gregoire, et al., Melting and metasomatism/refertilisation processes in the Patagonian sub-continental lithospheric mantle: A review, LITHOS(2019), https://doi.org/10.1016/j.lithos.2019.105324 This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier. Journal Pre-proof Melting and metasomatism/refertilisation processes in the Patagonian Sub-Continental Lithospheric Mantle: a review Massimiliano Melchiorrea,b, Barbara Faccinib*, Michel Gregoirec, Mathieu Benoitc, Federico Casettab, Massimo Coltortib a Institute of Earth Sciences Jaume Almera, CSIC, Carrer Luís Solé i Sabarís s/n, 08028 Barcelona, Spain. b Department of Physics and Earth Sciences, University of Ferrara, Via Saragat 1, 44121 Ferrara, Italy. c Géosciences Environnement Toulouse, Université de Toulouse; UPS OMP-CNRS-IRD, 14 Avenue E. Belin, 31400 Toulouse, France. *Corresponding author: Barbara Faccini, Department of Physics and Earth Sciences, University of Ferrara, Via Saragat 1, 44121 Ferrara, Italy. E-mail address: [email protected] Journal Pre-proof 1 Journal Pre-proof Melting and metasomatism/refertilisation processes in the Patagonian Sub-Continental Lithospheric Mantle: a review Abstract The large amount of geochemical variability in peridotitic and pyroxenitic xenoliths exhumed by Eocene to present-day magmas in Patagonia provides a unique opportunity to investigate the depletion and enrichment processes affecting the lithosphere in proximity of subduction settings and their relationships with magmatism. In this study, a review of the geochemical features of the Patagonian ultramafic xenoliths coupled with new Sr-Nd isotopic data on clinopyroxene separates from representative suites enabled us to delineate the main melt extraction and enrichment (metasomatism vs. refertilisation) processes acting in these sub-continental lithospheric mantle (SCLM) portions. Our findings show that clinopyroxenes and orthopyroxenes in Patagonian harzburgites/lherzolites lie on two discrete Al2O3/Mg# trends and record variable partial melting degrees (1-30%), progressively decreasing southward, where the mantle domains experienced melt extraction in the past. The occurrence of both negative and positive correlations between (La/Yb)N, SrN, and Al2O3 in clinopyroxenes suggests that large part of the SCLM beneath Patagonia was affected by both metasomatic (low melt-fluid/rock ratio) and refertilisation (high melt-fluid/rock ratio or long-lasting low melt-fluid/rock interaction) processes, while a few portions - particularly in Southern Patagonia - were devoid of significant enrichment processes. A comprehensive study of the major/trace element compositiJournalon and rare earth Pre-proof element patterns of clinopyroxene from both cumulitic and mantle xenoliths led us to hypothesize that tholeiitic enrichment was followed by infiltration of transitional/alkaline agents in the Northern and Central Patagonian SCLM. The percolation of melts with transitional affinity can be identified in some Central Patagonian localities. In Southern Patagonia clinopyroxenes record a slight interaction with alkaline and proto-adakitic agents; the latter occurred at Cerro Fraile, the locality nearest the trench. The Sr-Nd xenolith isotopic signature led to speculation that enriched and depleted mantle components interacted variably in the SCLM domain beneath Patagonia. This work suggests that a detailed and comprehensive study of 2 Journal Pre-proof ultramafic xenoliths can help identify the evidence produced by magmatic events occurring at the surface, as both a serial affinity and a temporal sequence. Keywords: Patagonia, Sub-Continental Lithospheric Mantle, alkaline metasomatism, tholeiitic refertilisation 1. Introduction The mantle xenoliths brought to the surface in the proximity of subduction settings are a powerful tool to investigate the depletion and enrichment processes affecting the lithospheric mantle. The dehydration of the subducting slab can lower the melting point of the overlying mantle wedge and trigger melt extraction (depletion processes). Enrichment processes are instead ascribed to the release of fluids/melts that modify the chemical composition of the mantle by adding incompatible elements (in some cases changing the major element budget as well) and eventually affecting its isotopic composition. Once transported to the surface, mantle xenoliths can signal these depletion and/or enrichment processes; the former are related to partial melting and the latter to both metasomatic and refertilisation events. Patagonia is a key locality for investigating depletion/enrichment processes affecting the mantle wedge in the proximity of a subducting slab. Throughout the entire Patagonian region, from the Eocene to the present, plateau magmatism with tholeiitic to transitional/alkaline affinity transported large amountsJournal of peridotitic Pre-proof and pyroxenitic xenoliths from the underlying lithosphere to the surface (Fig. 1). The large geochemical variability of these xenoliths provides evidence for moderate to strong depletion events (up to 30% partial melting) affecting the sub- continental lithospheric mantle (SCLM) wedge beneath Patagonia and for subsequent variable metasomatic/refertilisation processes (Aliani et al., 2009; Bjerg et al., 2005, 2009; Conceicao et al., 2005; Dantas, 2007; Dantas et al., 2009; Faccini et al., 2013; Gorring and Kay, 2000; Kilian and Stern, 2002; Laurora et al., 2001; Melchiorre et al., 2015; Mundl et al., 2015, 2016; Ntaflos et al., 2007; Rivalenti et al., 2004, 2007; Schilling et al., 2005, 2008, 2017; Stern et al., 1999). Nevertheless, 3 Journal Pre-proof the nature and provenance of fluids/melts pervading this mantle wedge is still debated, while a comprehensive model of the depletion and enrichment processes affecting the Patagonian SCLM is still far from settled. In some localities, the interaction between slab-derived fluids and previously depleted mantle domains is evidenced by the presence of modal amphibole and phlogopite (Comallo and Gobernador Gregores, n. 6 and 20 in Fig. 1, respectively; Laurora et al., 2001; Mundl et al., 2016). The occurrence of slab-derived
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