Overprinting orogenic events, ductile extrusion and strain partitioning during Caledonian transpression, NW Mainland Shetland

Armitage, Timothy B.; Holdsworth, Robert E.; Strachan, Robin A.; Dempsey, Edward D.; Walker, Richard J.; Alvarez-Ruiz, Diana T.; Lloyd, Geoffrey E.. 2024 Overprinting orogenic events, ductile extrusion and strain partitioning during Caledonian transpression, NW Mainland Shetland. Journal of Structural Geology, 180, 105088. 10.1016/j.jsg.2024.105088

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Official URL: http://dx.doi.org/10.1016/j.jsg.2024.105088

Abstract/Summary

A 3.6 km thick stack of mid-crustal deformed Precambrian rocks is associated with the North Roe Nappe (NRN) and Walls Boundary Fault in the northernmost Scottish Caledonides on NW Mainland Shetland. The greenschist- to amphibolite-facies rocks display unusually complex and heterogeneous combinations of coaxial and non-coaxial transpressional deformation. Previously published isotopic dating, together with new detailed field mapping and microstructural characterisation show that the NRN preserves a record of Neoarchaean, Neoproterozoic (Knoydartian) and Ordovician-Silurian (Caledonian) overprinting deformation and metamorphism. Neoarchaean events in the Uyea Gneiss Complex located in its footwall are reworked by younger events in the overlying nappe pile. The main ductile fabrics were formed during Caledonian top-to-the W/NW thrusting and top-to-the N sinistral shearing, with subordinate regions of top- to-the E extensional and NNE-SSW dextral shearing. In lower parts of the NRN, these different kinematic domains are texturally indistinguishable and overprinting relationships are absent. At higher levels, top-to-the-W/NW thrust-related fabrics are consistently overprinted by top-to-the-N/NE sinistral shearing. The highly partitioned transpressional deformation shows similarities with equivalent rocks of the Moine Nappe in NW Scotland.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/j.jsg.2024.105088
ISSN:	01918141
Date made live:	29 Feb 2024 14:58 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/537002

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1016/j.jsg.2024.105088

ISSN:

01918141

Date made live:

29 Feb 2024 14:58 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/537002