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Jurassic ophiolites within the Valais domain of the Western and Central Alps: geochronological evidence for re-rifting of oceanic crust

Liati, Anthi; Froitzheim, Nikolaus; Fanning, Christopher

Description

Metabasic rocks from different parts of the Antrona ophiolites, Western Alps, as well as from the Misox zone, Central Alps, were dated using ion microprobe (SHRIMP) U-Pb analyses of zircon, in association with cathodoluminescence (CL) imaging. HP metamorphism must have affected at least the major part of the Antrona ophiolites, although HP relics are rarely preserved, probably due to the Lepontine metamorphic overprint. HP metamorphism has affected also the area of the Misox zone. The origin of...[Show more]

dc.contributor.authorLiati, Anthi
dc.contributor.authorFroitzheim, Nikolaus
dc.contributor.authorFanning, Christopher
dc.date.accessioned2015-12-13T23:00:27Z
dc.identifier.issn0010-7999
dc.identifier.urihttp://hdl.handle.net/1885/84130
dc.description.abstractMetabasic rocks from different parts of the Antrona ophiolites, Western Alps, as well as from the Misox zone, Central Alps, were dated using ion microprobe (SHRIMP) U-Pb analyses of zircon, in association with cathodoluminescence (CL) imaging. HP metamorphism must have affected at least the major part of the Antrona ophiolites, although HP relics are rarely preserved, probably due to the Lepontine metamorphic overprint. HP metamorphism has affected also the area of the Misox zone. The origin of the Antrona ophiolites is arguable. They were interpreted as part of both the Piemont-Ligurian (PL) and the Valais ocean, the two main oceans in the area of the Alps before Alpine convergence. SHRIMP-analyses of co-magmatic zircon domains from the Antrona ophiolites (Guggilihorn, Passo del Mottone and Quarata areas) yielded identical (within uncertainty) weighted mean 206Pb/238U ages of 155.2 ± 1.6 Ma, 158 ± 17 Ma (or 163.1 ± 2.4 Ma: one analysis; 1σ error) and 155.6 ± 2.1 Ma, respectively, interpreted as the time of crystallization of the magmatic protoliths. These Late Jurassic ages fit well to the time span considered for the formation of Piemont-Ligurian oceanic crust. The metagabbro of the Misox zone (Hinterrhein area), for which a Valaisan origin is generally accepted, gave also a Late Jurassic, PL protolith age of 161.0 ± 3.9 Ma. The metamorphic zircon domains from the amphibolitized eclogite of Mottone yielded an age of 38.5 ± 0.7 Ma, interpreted as the time of HP metamorphism. This age is in good agreement with the time of metamorphism reported from previous zircon SHRIMP-data for eclogites and amphibolites of other parts in the Valais domain. In order to bring in line the PL protolith ages with the Valaisan metamorphic ages, we suggest a scenario involving emplacement of part of the PL oceanic crust to the north of the newly formed Briançonnais peninsula, inside the Valais geotectonic domain. This paleotectonic configuration was probably established when younger Valaisan oceanic crust formed by spreading and re-rifting, partly within PL oceanic crust.
dc.publisherSpringer
dc.sourceContributions to Mineralogy and Petrology
dc.subjectKeywords: geochronology; Jurassic; oceanic crust; ophiolite; rifting; Alps; Central Alps; Eastern Hemisphere; Eurasia; Europe; Western Alps; World
dc.titleJurassic ophiolites within the Valais domain of the Western and Central Alps: geochronological evidence for re-rifting of oceanic crust
dc.typeJournal article
local.description.notesImported from ARIES
local.description.refereedYes
local.identifier.citationvolume149
dc.date.issued2005
local.identifier.absfor040303 - Geochronology
local.identifier.absfor040313 - Tectonics
local.identifier.ariespublicationMigratedxPub12393
local.type.statusPublished Version
local.contributor.affiliationLiati, Anthi, ETH Zurich
local.contributor.affiliationFroitzheim, Nikolaus, University of Bonn
local.contributor.affiliationFanning, Christopher, College of Physical and Mathematical Sciences, ANU
local.description.embargo2037-12-31
local.bibliographicCitation.startpage446
local.bibliographicCitation.lastpage461
local.identifier.doi10.1007/s00410-005-0658-7
dc.date.updated2015-12-12T07:34:12Z
local.identifier.scopusID2-s2.0-21044441520
CollectionsANU Research Publications

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