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Metamorphic evolution of the Briançonnais units along the ECORSCROP profile (Western Alps) : new data on metasedimentary rocks

Bucher, S. and Bousquet, R.. (2007) Metamorphic evolution of the Briançonnais units along the ECORSCROP profile (Western Alps) : new data on metasedimentary rocks. Swiss Journal of Geosciences, Vol. 100. pp. 227-242.

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Official URL: http://edoc.unibas.ch/dok/A5250566

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Abstract

Briançonnais units are squeezed between two Mesozoic eclogitic belts (Piemont-Ligurian ocean and Valaisan ocean) along the ECORS-CROP seismic line in the Italian-French Western Alps (France, Italy). The metamorphic evolution of this area plays a key role for understanding the evolution of the Western Alps and is discussed on the basis of detailed petrographic investigations carried out on weathered sediments issued from the erosion of the Hercynian belt, especially on lower Permian to Mesozoic sediments. In the Zone Houillère, as well in the Permo-Triassic cover of the Briançonnais basement, the index metamorphic mineral assemblage is mainly composed of white micas with varying chemical composition, chloritoid and garnet. This same assemblage occurs within different lithologies (metaarkose, metapelite, metasandstone). Consequently, equilibrium phase diagrams were computed for different whole rock compositions using DOMINO software. The results of the P-T investigations clearly show that each unit underwent a different sequence of metamorphic reactions. An increase in metamorphic grade from greenschist facies conditions in the Northwest (Zone Houillère) to the transition between blueschist and eclogite facies conditions in the Southeast (Internal Briançonnais) is observed. A major discontinuity in metamorphic grade is located at the contact between Zone Houillère and Ruitor unit, as documented by a pressure gap of ~ 7 kbar. In general, the observed metamorphic field gradient is inverted and is interpreted to represent different depths of burial during subduction, which correlates with the paleogeographic position of the different units.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Geologie-Paläontologie > Tektonik (nn)
UniBasel Contributors:Bousquet, Romain
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:Birkhäuser
ISSN:1661-8726
Note:Publication type according to Uni Basel Research Database: Journal article
Last Modified:22 Mar 2012 14:28
Deposited On:22 Mar 2012 14:01

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