U–Pb geochronology of deformed metagranites in central Sutherland, Scotland: evidence for widespread late Silurian metamorphism and ductile deformation of the Moine Supergroup during the Caledonian orogeny

2003/03/01 by P. D. Kinny, P.D. Kinny, R. A. Strachan +7 · 9 citations
Earth and Planetary Sciences · Computer Science · #Geological and Geochemical Analysis #earthquake and tectonic studies #Geochemistry and Geologic Mapping

paper · doi:10.1144/0016-764901-087

Abstract

Within the Caledonides of central Sutherland, Scotland, the Neoproterozoic metasedimentary rocks of the Moine Supergroup record NW-directed D 2 ductile thrusting and nappe assembly, accompanied by widespread tight-to-isoclinal folding and amphibolite-facies metamorphism. A series of metagranite sheets which were emplaced and penetratively deformed during D 2 have been dated using SHRIMP U–Pb geochronology. Zircon ages of 424 ± 8 Ma (Vagastie Bridge granite), 420 ± 6 Ma (Klibreck granite) and 429 ± 11 Ma (Strathnaver granite) are interpreted to date emplacement, and hence regional D 2 deformation, during mid- to late Silurian time. Titanite ages of 413 ± 3 Ma (Vagastie Bridge granite) and 416 ± 3 Ma (Klibreck granite) are thought to date post-metamorphic cooling through a blocking temperature of c . 550–500 °C. A mid- to late Silurian age for D 2 deformation supports published models that have viewed the internal ductile thrusts of this part of the orogen as part of the same kinematically linked system of foreland-propagating thrusts as the marginal Moine Thrust Zone. The new data contrast with previous interpretations that have viewed the dominant structures and metamorphic assemblages within the Moine Supergroup as having formed during the early to mid-Ordovician Grampian arc–continent orogeny. The mid- to late Silurian D 2 nappe stacking event in Sutherland is probably a result of the collision of Baltica with the Scottish segment of Laurentia.

Citations

• Relationships between marginal thrusting and movement on major, internal shear zones in the Northern Highland Caledonides, Scotland
• Precambrian and Palaeozoic pegmatites in the Moines of northern Scotland
• Sinistral transpression and the Silurian closure of Iapetus
• Direct dating of mylonite evolution: a multi-disciplinary geochronological study from the Moine Thrust Zone, NW Scotland

Cited by

• Patterns of Silurian deformation and magmatism during sinistral oblique convergence, northern Scottish Caledonides
• A discussion of possible heat sources during nappe stacking: the origin of Barrovian metamorphism within the Caledonian thrust sheets of NW Scotland
• Thermal evolution of the Scandian hinterland, Naver nappe, northern Scotland
• Prolonged high-temperature Caledonian metamorphism in the southern part of the Northern Highlands terrane, Scotland, indicated by integrated monazite and xenotime laser ablation split-stream petrochronology and thermometry
• Thermobarometry of the Moine and Sgurr Beag thrust sheets, northern Scotland
• Changing Silurian–Devonian relative plate motion in the Caledonides: sinistral transpression to sinistral transtension
• Geochronology and geodynamics of Scottish granitoids from the late Neoproterozoic break-up of Rodinia to Palaeozoic collision
• Lu–Hf and Sm–Nd dating of metamorphic garnet: evidence for multiple accretion events during the Caledonian orogeny in Scotland
• Evidence for 930 Ma metamorphism in the Shetland Islands, Scottish Caledonides: implications for Neoproterozoic tectonics in the Laurentia–Baltica sector of Rodinia

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• U–Pb geochronology of regional migmatites in East Sutherland, Scotland: evidence for crustal melting during the Caledonian orogeny
• Tectonic evolution of the Caledonian orogeny in Scotland: a review based on the timing of magmatism, metamorphism and deformation
• Dating deformation and cooling in the Caledonian thrust nappes of north Sutherland, Scotland: insights from 40 Ar/ 39 Ar and Rb–Sr chronology
• U–Pb geochronology of the Fort Augustus granite gneiss: constraints on the timing of Neoproterozoic and Palaeozoic tectonothermal events in the NW Highlands of Scotland
• Patterns of Silurian deformation and magmatism during sinistral oblique convergence, northern Scottish Caledonides