Polyphase structural, intrusive and metamorphic evolution of the Bockfjorden area, NW Spitsbergen

Details

Serval ID
serval:BIB_3CDDF23C33EC
Type
Article: article from journal or magazin.
Collection
Publications
Title
Polyphase structural, intrusive and metamorphic evolution of the Bockfjorden area, NW Spitsbergen
Journal
Schweizerische Mineralogische und Petrographische Mitteilungen
Author(s)
Wyss M., Hermann J., Muntener O., Benning L.
ISSN-L
0036-7699
Publication state
Published
Issued date
1998
Peer-reviewed
Oui
Volume
78
Pages
87-106
Language
english
Abstract
Structures, intrusive contacts and metamorphic mineral assemblages
reveal a polyphase tectonothermal evolution for the Caledonian basement
rocks of the Bockfjorden area, NW Spitsbergen. The oldest deformation
D-1 is documented by isoclinal folds F-1 in biotite schist. F-1 folds
are crosscut by an intrusion I-1 of tonalitic to monzogranitic
composition. Both, F-1 folds and I-1 are overprinted by D-2 structures,
that are considered to be related to the Silurian Caledonian
continental collision. D-1 and I-1 are thus regarded as the record of a
complex pre-Silurian evolution of the basement rocks. The Caledonian
continental collision that is represented by the isoclinal folding F-2
and by the main schistosity S-2 was simple shear dominated and
associated to S-N thrusting in the studied area. During D-2 the I-1
granitoid rocks were transformed to orthogneiss. The related
metamorphism M-2 reached upper amphibolite facies conditions. During or
after late stage (2), deformation the orthogneiss provides evidence for
incipient partial melting. The resulting migmatites and S-2 were
subsequently crosscut by the granodiorite and monzogranite of the
intrusive event I-2, that display partly a peraluminous composition,
pointing to partial melting of crustal rocks as the magma source.
Subsequently, cordierite formed in all Al-rich rock types including I-1
and I-2 rocks. Cordierite growth was caused by a high T-low P
metamorphism at conditions of 630-700 degrees C and 0.3-0.4 GPa, the
geotherm of which was about 50 degrees/km. The transition from
migmatite formation to granite emplacement followed by a high T-low P
metamorphism indicates near isothermal decompression under upper
amphibolite facies conditions. This evolution reflects a continuous
exhumation of mid-crustal rocks that is considered as the consequence
of crustal extension during the collapse of Caledonian thickened crust.
Create date
17/04/2009 23:56
Last modification date
20/08/2019 13:33
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