The Geochemical Complexity of Kimberlite Rocks and their Olivine Populations: a Reply to the Comment on Cordieret al.(2015) by Andrea Giuliani & Stephen F. Foley

Autor: Carole Cordier, Valentina Batanova, Anne-Marie Boullier, Lucie Sauzéat, Fabrice Barou, Nicholas Arndt
Přispěvatelé: Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Géosciences Montpellier, Institut national des sciences de l'Univers (INSU - CNRS)-Université de Montpellier (UM)-Université des Antilles (UA)-Centre National de la Recherche Scientifique (CNRS)
Rok vydání: 2016
Předmět:
Zdroj: Journal of Petrology
Journal of Petrology, Oxford University Press (OUP), 2016, 57 (5), pp.927-931. ⟨10.1093/petrology/egw027⟩
ISSN: 1460-2415
0022-3530
Popis: International audience; We thank sincerely Giuliani & Foley for their discussion of the textures and compositions of olivine in kimberlites. We do not agree with many of their interpretations and therefore welcome the chance to respond, particularly because it provides an opportunity to explain once again the characteristics of olivine in kimberlites that we think are most important—features that have commonly been misinterpreted or overlooked in many other papers. In publications such as those by Kamenetsky et al. (2008), Brett et al. (2009) or Pilbeam et al. (2013), the emphasis has been on mineral compositions and internal zonation whereas in our paper (Cordier et al., 2015) and in an earlier study (Arndt et al., 2010), we emphasized the internal structures and fabrics of olivine grains. In the earlier paper, we described structures produced by solid-state deformation and showed that these could only have formed in the lithosphere. In our 2015 paper, we focused on grain boundary migration zones. These features, which typically develop during fluid-assisted recrystallization, may be unfamiliar to igneous petrologists but are well known to metamorphic and structural geologists. Like the internal deformation features, they form slowly or under high-stress conditions and could only have been produced within the lithosphere. We emphasize that these deformation or recrystallization features formed within rock of dunitic composition: the orthopyroxene, clinopyroxene and garnet–spinel that make up a large proportion of most mantle xenoliths were absent when these textures originated. In our opinion, these observations indicate clearly that orthopyroxene was eliminated before entrainment of xenoliths into the ascending kimberlite magma. If this interpretation is correct (and we have not heard or read any arguments to negate it), it calls into question the commonly accepted model that proposes loss of orthopyroxene within ascending kimberlite magma.
Databáze: OpenAIRE
Externí odkaz: