1 Mid-Devonian sinistral transpressional movements on the Great Glen 2 Fault: the rise of the Rosemarkie Inlier and the Acadian Event in 3 Scotland. 4 5 J.R. Mendum1 & S.R. Noble2 6 1British Geological Survey, Murchison House, West Mains Road, Edinburgh, EH9 3LA 7 2NERC Isotope Geosciences Laboratory, British Geological Survey, Kingsley Dunham 8 Centre, Keyworth, Nottingham, NG12 5GG 9 e-mail:
[email protected] 10 11 Abstract 12 The Rosemarkie Inlier is a small fault-bounded lens of interleaved Moine psammites and 13 possible Lewisianoid orthogneisses with distinctive leucogranite veins and pods that lies 14 adjacent to the Great Glen Fault (GGF). The basement rocks and most of the 15 leucogranites are strongly deformed and tightly folded with foliations generally steeply 16 dipping and a locally well-developed NE-plunging rodding lineation. Mid-Devonian 17 sandstone and conglomerate unconformably overlie the inlier on its western side. 18 Monazite from a deformed leucogranite vein gave a mean ID-TIMS 207Pb/235U age of 19 397.6 ± 2.2 Ma and acicular zircons gave a compatible concordant ID-TIMS U-Pb age of 20 400.8 ± 2.6 Ma, dating emplacement as mid-Devonian. Xenocrystic zircons from the 21 leucogranites and complex zoned zircons from two adjacent tonalitic gneisses gave LA- 22 MC-ICP-MS concordant ages between 2720 and 2930 Ma confirming their Archaean 23 Lewisianoid origin. Leucogranite emplacement is interpreted to mark the onset of 24 Acadian transpression and sinistral strike-slip movement on the GGF that resulted in 25 multi-phase deformation and oblique exhumation of the Rosemarkie Inlier.