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Exhumation of high‐pressure rocks beneath the Solund Basin, Western Gneiss Region of Norway
Author(s) -
Hacker B. R.,
Andersen T. B.,
Root D. B.,
Mehl L.,
Mattinson J. M.,
Wooden J. L.
Publication year - 2003
Publication title -
journal of metamorphic geology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.639
H-Index - 114
eISSN - 1525-1314
pISSN - 0263-4929
DOI - 10.1046/j.1525-1314.2003.00468.x
Subject(s) - geology , allochthon , geochemistry , gneiss , ophiolite , metamorphism , orogeny , subduction , massif , eclogite , shear zone , metamorphic facies , fault (geology) , blueschist , petrology , tectonics , geomorphology , nappe , metamorphic rock , seismology , facies , structural basin
The Solund–Hyllestad–Lavik area affords an excellent opportunity to understand the ultrahigh‐pressure Scandian orogeny because it contains a near‐complete record of ophiolite emplacement, high‐pressure metamorphism and large‐scale extension. In this area, the Upper Allochthon was intruded by the c. 434 Ma Sogneskollen granodiorite and thrust eastward over the Middle/Lower Allochthon, probably in the Wenlockian. The Middle/Lower Allochthon was subducted to c. 50 km depth and the structurally lower Western Gneiss Complex was subducted to eclogite facies conditions at c. 80 km depth by c. 410–400 Ma. Within < 5–10 Myr, all these units were exhumed by the Nordfjord–Sogn detachment zone, producing shear strains > 100. Exhumation to upper crustal levels was complete by c. 403 Ma. The Solund fault produced the last few km of tectonic exhumation, bringing the near‐ultrahigh‐pressure rocks to within c. 3 km vertical distance from the low‐grade Solund Conglomerate.