Exhumation of the high‐pressure Richarddalen Complex in <scp>NW</scp> Svalbard: Insights from <scp> 40 Ar</scp>/<scp> 39 Ar</scp> geochronology

• Published in: Terra Nova
• Main Authors: Mazur, Stanislaw, Majka, Jarosław, Barnes, Christopher J., McClelland, William, Bukała, Michał, Janák, Marian, Kośmińska, Karolina
• Other Authors: Narodowe Centrum Nauki
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2022
• Subjects: Geology; Svalbard
• Online Access: http://dx.doi.org/10.1111/ter.12597; https://onlinelibrary.wiley.com/doi/pdf/10.1111/ter.12597; https://onlinelibrary.wiley.com/doi/full-xml/10.1111/ter.12597

Abstract 40 Ar/ 39 Ar dating of white mica from foliated metamorphic rocks of the Caledonian orogen of NW Svalbard was performed using the single‐grain fusion technique. Two samples, an augen orthogneiss and a mica schist, were collected from the high‐pressure Richarddalen Complex. Three additional mica schist samples were collected from the tectonically underlying Montblanc Unit. 40 Ar/ 39 Ar analysis of white mica separates yielded weighted average 40 Ar/ 39 Ar dates of 446.1 ± 1.1, 438.4 ± 1.1, 439.4 ± 1.2, 439.8 ± 1.5 and 439.3 ± 1.0 Ma, with the oldest date provided by the Richarddalen mica schist. The single‐grain fusion 40 Ar/ 39 Ar dating was accompanied by geochemical mapping of white mica using a microprobe. We interpret the oldest date as the age of cooling after a Late Ordovician high‐pressure event and the four younger dates to represent the timing of subsequent deformation associated with assembly of a Caledonian nappe stack.