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The nature and significance of the Faroe-Shetland Terrane: Linking Archaean basement blocks across the North Atlantic

Holdsworth, R.E.; Morton, A.; Frei, D.; Gerdes, A.; Strachan, R.A.; Dempsey, E.; Warren, C.; Whitham, A.

Authors

R.E. Holdsworth

A. Morton

D. Frei

A. Gerdes

R.A. Strachan

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Dr Eddie Dempsey E.Dempsey@hull.ac.uk
Lecturer in Structural Geology, Programme Director (Geology and GPG)

C. Warren

A. Whitham



Contributors

Abstract

Core samples of the continental basement rocks that underlie the eastern Faroe-Shetland Basin (FSB) and its inshore margins west of Shetland reveal a suite of predominantly granodioritic to granitic orthogneisses (including TTG), together with lesser volumes of foliated granitoids and subordinate dioritic to mafic gneisses and amphibolites. A small area of lithologically similar gneisses also crops out onshore at North Roe/Uyea west of the Caledonian front in Shetland. Coarse grained gneissose textures and mineralogies consistent with upper amphibolite facies metamorphism are overprinted by a weak, but ubiquitous static greenschist facies retrogression. Later structures include widespread epidote-quartz veining, and local developments of mylonite, cataclasite, pseudotachylite and phyllonite. Regions associated with the Rona Ridge oil fields (e.g. Clair, Lancaster) also preserve extensive brittle fracturing and associated low temperature hydrothermal mineralization (quartz, adularia, calcite, pyrite/chalcopyrite) with significant fracture-hosted hydrocarbons. New and published U-Pb zircon analyses from the gneisses offshore give a relatively narrow range of Neoarchean protolith ages (ca 2.7-2.8 Ga) spread over a geographic area of 60,000km2 west of Shetland. Detrital zircon data from overlying Triassic-Cretaceous sedimentary sequences in the FSB suggest an equivalent limited range of Neoarchean source materials. Our findings suggest that a major phase of Neoarchean crustal formation and associated high grade metamorphism dominates basement rocks in the region. They are similar in age and lithology to the protoliths of the nearest onshore Lewisian Complex of NW Scotland (Rhiconich Terrane). However, they lack geochronological or textural evidence for the widespread Proterozoic Laxfordian events (ca 1.7-1.8 Ga) which are widespread in Scotland. This suggests that the Precambrian rocks west of Shetland – the Faroe-Shetland Terrane-can be correlated with the Archean rocks of the Central Greenland-Rae Craton and that a northern limit of Proterozoic reworking lies just offshore from the north coast of Scotland.

Citation

Holdsworth, R., Morton, A., Frei, D., Gerdes, A., Strachan, R., Dempsey, E., …Whitham, A. (2019). The nature and significance of the Faroe-Shetland Terrane: Linking Archaean basement blocks across the North Atlantic. Precambrian research, 321, 154-171. doi:10.1016/j.precamres.2018.12.004

Journal Article Type Article
Acceptance Date Dec 5, 2018
Online Publication Date Dec 6, 2018
Publication Date Feb 1, 2019
Deposit Date Dec 17, 2018
Publicly Available Date Dec 7, 2019
Print ISSN 0301-9268
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 321
Pages 154-171
DOI https://doi.org/10.1016/j.precamres.2018.12.004
Keywords Lewisian; Faroe-Shetland; Neoarchean; Nagssugtoqidian; Laxfordian; U-Pb geochronology
Public URL https://hull-repository.worktribe.com/output/1155157
Publisher URL https://www.sciencedirect.com/science/article/pii/S0301926818302754?via%3Dihub

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