Ordovician-Silurian deformation of the Neoproterozoic upper gneiss unit in the northern Seve Nappe Complex: implications for subduction of the Baltican margin

Ordovician-Silurian deformation of the Neoproterozoic upper gneiss unit in the northern Seve Nappe Complex : implications for subduction of the Baltican margin

Majka, Jaroslaw (author): Uppsala universitet,Institutionen för geovetenskaper,AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.

Callegari, Riccardo (author): Uppsala universitet,Institutionen för geovetenskaper,AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.

Walczak, K. (author): AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, Krakow, Poland.

Polish Acad Sci, Inst Geol Sci, Krakow, Poland Institutionen för geovetenskaper (creator_code:org_t)

Geological Society of London, 2023
2023
English.
In: Journal of the Geological Society. - : Geological Society of London. - 0016-7649 .- 2041-479X. ; 180:4

Related links:: https://urn.kb.se/re...; show more...; https://doi.org/10.1...; show less...

Abstract Subject headings

The upper gneiss unit is exposed in the northernmost Seve Nappe Complex (SNC) in the Scandinavian Caledonides. To investigate the Caledonian tectonic history of the unit, in situ white mica and biotite Ar-40/Ar-39 geochronology was applied to a leucogranite and two paragneisses. The leucogranite exhibits low-strain traits. Biotite porphyroblasts yielded a cooling age of 459 +/- 2 Ma. White mica that replace biotite and plagioclase provided a crystallization age of 436 +/- 5 Ma. White mica in both paragneisses exhibit high-strain characteristics associated with top-to-the-east sense of shear. One paragneiss provided dispersed late Cambrian to Late Ordovician dates with the youngest approximating deformation at 459 +/- 2 Ma. The older dates are interpreted to reflect Ar-40 inherited from a previous metamorphic event. The second paragneiss yielded a deformation age of 434 +/- 2 Ma. The collective dataset is interpreted to record exhumation of the upper gneiss unit at c. 459 Ma and deformation and fluid infiltration at c. 434 Ma during continental collision. The events closely resemble the deformation histories of other northern SNC terranes. Synthesizing these results with those for other northern SNC terranes suggests that the Baltican margin underwent oblique, south-to-north subduction during late Cambrian time.

By the author/editor: Barnes, C. J.; Majka, Jaroslaw; Callegari, Ricca ...; Walczak, K.; Ziemniak, G.; Bukala, M.

About the subject

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