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Mylonites of the South Armorican Shear Zone: Insights for crustal-scale fluid flow and water-rock interaction processes

Tartese, Romain; Boulvais, Philippe; Poujol, Marc; Chevalier, Thomas; Paquette, Jean-Louis; Ireland, Trevor; Deloule, Etienne

Description

Mylonites display petrographical and geochemical characteristics that can be related to syn-deformation fluid circulation. The South Armorican Shear Zone, a major structural feature of the Armorican Massif (France), is outlined by the presence of mylonitic rocks cropping out mostly in open quarries. These mylonites were essentially formed at the expense of peraluminous granitic bodies. Deformation occurred from ductile conditions in the biotite stability field (>400°C) down to lower greenschist...[Show more]

dc.contributor.authorTartese, Romain
dc.contributor.authorBoulvais, Philippe
dc.contributor.authorPoujol, Marc
dc.contributor.authorChevalier, Thomas
dc.contributor.authorPaquette, Jean-Louis
dc.contributor.authorIreland, Trevor
dc.contributor.authorDeloule, Etienne
dc.date.accessioned2015-12-10T23:36:25Z
dc.identifier.issn0264-3707
dc.identifier.urihttp://hdl.handle.net/1885/70123
dc.description.abstractMylonites display petrographical and geochemical characteristics that can be related to syn-deformation fluid circulation. The South Armorican Shear Zone, a major structural feature of the Armorican Massif (France), is outlined by the presence of mylonitic rocks cropping out mostly in open quarries. These mylonites were essentially formed at the expense of peraluminous granitic bodies. Deformation occurred from ductile conditions in the biotite stability field (>400°C) down to lower greenschist cataclasis and brecciation, where carbonation developed. U-Pb analyses on zircon and monazite define a minimum duration of 15Ma for the deformation and hydrothermal history, between 315Ma and 300Ma. Fluid circulations are well documented, by way of petrographic observation (chlorite and carbonate crystallization), mineralogical composition analysis (muscovite chemistry), erratic mobility behavior of some elements (As, Sn, U for instance), and stable isotope composition analysis of the infiltrated rocks. High temperature deformation is not accompanied by alteration of the O isotope system, which implies either low fluid/rock ratio and/or the involvement of δ 18O crustal fluids with a composition similar to that of the rocks. On the other hand, some low temperature mylonites show a drastic decrease in the δ 18O values, which has to be related to the influx of surface derived waters. The heat source necessary for this crustal scale downward infiltration of fluids followed by upward motion was likely provided by the exhumation of lower crustal units in the South Armorican domain.
dc.publisherPergamon-Elsevier Ltd
dc.sourceJournal of Geodynamics
dc.subjectKeywords: crustal structure; ductile deformation; element mobility; exhumation; fluid flow; geochemistry; greenschist; isotopic composition; mineralogy; mylonite; oxygen isotope; petrology; shear zone; stable isotope; uranium series dating; uranium-lead dating; wat Elementary mobility; Fluid circulation; Mylonites; O isotopes; South Armorican Shear Zone; U-Th-Pb dating
dc.titleMylonites of the South Armorican Shear Zone: Insights for crustal-scale fluid flow and water-rock interaction processes
dc.typeJournal article
local.description.notesImported from ARIES
local.identifier.citationvolume56-57
dc.date.issued2012
local.identifier.absfor040303 - Geochronology
local.identifier.absfor040203 - Isotope Geochemistry
local.identifier.absfor040313 - Tectonics
local.identifier.ariespublicationf2965xPUB2226
local.type.statusPublished Version
local.contributor.affiliationTartese, Romain, Universite de Rennes
local.contributor.affiliationBoulvais, Philippe, CNRS-Univsite de Rennes
local.contributor.affiliationPoujol, Marc, Université de Rennes 1
local.contributor.affiliationChevalier, Thomas, Universite de Rennes
local.contributor.affiliationPaquette, Jean-Louis, Universite Blaise Pascal
local.contributor.affiliationIreland, Trevor, College of Physical and Mathematical Sciences, ANU
local.contributor.affiliationDeloule, Etienne, CRPG-CRNS
local.description.embargo2037-12-31
local.bibliographicCitation.startpage86
local.bibliographicCitation.lastpage107
local.identifier.doi10.1016/j.jog.2011.05.003
local.identifier.absseo970104 - Expanding Knowledge in the Earth Sciences
dc.date.updated2016-02-24T08:23:32Z
local.identifier.scopusID2-s2.0-84855376562
local.identifier.thomsonID000302422700007
CollectionsANU Research Publications

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