Age of the Loch Borrolan complex, Assynt, and late movements along the Moine Thrust Zone

O. van Breemen, M. Aftalion and M. R. W. Johnson
Journal of the Geological Society, 136, 489-495, 1 July 1979, https://doi.org/10.1144/gsjgs.136.4.0489

Abstract

U-Pb analyses of zircons from 4 intrusions of the Loch Borrolan alkaline igneous complex in the Moine Thrust Zone closely define a discordia corresponding to an upper intersection age of 430 ± 4 Ma. No evidence has been found for an inherited radiogenic lead component. Structural relationships show that the error limits on the age bracket a late period of movement along one of the splays of the Moine Thrust. Alkaline igneous activity (documented back to 456 ± 5 Ma) along the western margin of the Caledonian Orogen in Scotland is related to crustal arching, directly and/or indirectly in response to orogenic compression. Synchronous thrusts directed towards the foreland appear to overtake the alkaline centres—thus resulting in their burial, metamorphism, deformation and/or transport. The change from alkaline to the more widespread (late Caledonian) granite magmatism appears to coincide with the end of thrust movement and the beginning of post-orogenic uplift.

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Journal of the Geological Society: 136 (4)
Journal of the Geological Society
Volume 136, Issue 4
July 1979
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