Origin of ultramafic–mafic bodies on the Isles of Lewis and Harris (Scotland, UK): Constraints on the Archean–Paleoproterozoic evolution of the Lewisian Gneiss Complex, North Atlantic Craton

Guice, George; Miocevich, Sophie R.; Hughes, Hannah S.R.; McDonald, Iain; Goodenough, Kathryn; Ackerson, Michael R.; MacDonald, John; Faithfull, John

doi:10.1016/j.precamres.2021.106523

Cited by 2 publications

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References 133 publications

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“…Synoptic time–space diagram reflecting a compilation of the major magmatic and metamorphic events (stars) in the three regions of the mainland LGC (modified after Guice et al, 2022). Question marks represent uncertainties.…”

Section: Regional Geologymentioning

confidence: 99%

“…The advent of in situ U-Pb spot analysis of zircon led researchers to propose a model for the LGC that departed from the simple tripartite subdivision, which envisaged the mainland LGC to be composed of up to six crustal blocks that amalgamated during the Laxfordian event (e.g., Friend & Kinny, 2001;Kinny et al, 2005). This terrane model is variably accepted, as well as the Laxfordian and the Gairloch Shear Zones (Figure 1) being major tectonic boundaries (Goodenough et al, 2010(Goodenough et al, , 2013Park, 2005), although debates about the number and position of terranes, their tectonic boundaries and their timing of amalgamation remain open (e.g., Fischer et al, 2021;Guice et al, 2022). In the granulite facies central region of the mainland LGC, amphibolite facies retrogression associated with the Inverian and Laxfordian overprinting stages is concentrated along crustal-scale shear zones (e.g., Corfu et al, 1994;Goodenough et al, 2013;Zirkler et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

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Constraints on the Palaeoproterozoic tectono‐metamorphic evolution of the Lewisian Gneiss Complex, NW Scotland: Implications for Nuna assembly

Volante,

Dziggel,

Walters

et al. 2023

Journal Metamorphic Geology

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Despite extensive investigation, the tectono‐thermal evolution of the Archean crust in the Lewisian Gneiss Complex in NW Scotland (LGC) is debated. Most U–Pb zircon geochronological and metamorphic studies have focused on rocks from the central region of the mainland LGC, where granulite facies assemblages associated with the oldest (Badcallian) tectono‐metamorphic event at c. 2.75 Ga are overprinted by younger amphibolite facies assemblages related to the Inverian (c. 2.5 Ga) and subsequent Laxfordian (c. 1.9–1.65 Ga) tectono‐thermal events. In the southern and northern regions of the mainland LGC, deformation and metamorphism associated with the Laxfordian event are pervasive, although the timing and conditions are poorly constrained. Here, we present new field, petrographic and structural data, U–Pb zircon and titanite geochronology and phase equilibrium modelling of amphibolite samples from the northern and southern regions. Our field observations show that in both regions, pre‐Laxfordian structures are significantly reworked by steep NW‐striking fabrics that are themselves pervasively overprinted by co‐axial deformation and amphibolite facies metamorphism related to the Laxfordian event. In situ U–Pb titanite geochronology yields Laxfordian ages of 1853 ± 20 Ma in the southern region (P = 6–8 kbar and T = 640–690°C) and 1750 ± 20 Ma and 1776 ± 10 Ma in the northern region (P = 6–7.5 kbar and T = 740–760°C). While U–Pb dating of zircon rims from felsic gneisses in the central region shows a dominant Inverian metamorphic overprint at c. 2500 Ma, zircon rims in felsic gneisses from the northern and southern regions commonly yield Laxfordian dates as young as c. 1800 Ma. Combined, the results support the idea that, during the Palaeoproterozoic, the central region of the LGC acted as low‐strain domain, in which intense deformation and metamorphism were restricted to crustal‐scale shear zones. By contrast, in the southern and northern regions, early (c. 1.85 Ga) and late (c. 1.75 Ga) Laxfordian deformation and fluid‐mediated metamorphism were much more pervasive and at higher P–T conditions than previously proposed. The diachronous Laxfordian evolution of the southern and northern regions indicate that they reflect early and late snapshots of collisional to transpressional tectonics in the mainland LGC. The long‐lasting Laxfordian evolution documents the collision of the Rae and North Atlantic cratons during the Palaeoproterozoic amalgamation of the supercontinent Nuna, with implications for the palaeogeographic configuration of NW Scotland during Palaeoproterozoic Nuna.

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Section: Regional Geologymentioning

confidence: 99%