|
Article |
1 Department of Geology and Applied Geology, University of Glasgow, Glasgow G12 8QQ, UK
2 Department of Earth Sciences, University of Derby, Derby DE3 IGB, UK
3 Isotope Geosciences Unit, Scottish Universities Research and Reactor Centre, East Kilbride, Glasgow G75 0QU UK
The Buchan area of Dalradian rocks represents a distinct tectonothermal domain within the Scottish Highlands, and the Portsoy-Duchray Hill lineament on the western margin of this block is one of the best examples of a long-lived domain boundary. Rb-Sr mica cooling ages, from metamorphic rocks from across the trace of this lineament, document a prolonged Ordovician cooling history. Delayed, but then relatively rapid, cooling to the west of the Portsoy-Duchray Hill lineament is recognized whereas to the east the age data point to a high heat flow regime lasting more than 50 Ma. The isotopic ages suggest that c. 460 Ma was a time of active tectonism, resulting in final cooling of the low-grade rocks and differential uplift and rapid cooling of deeper structural levels to the west. The radiometric ages do not support previous tectonic models for the region that have invoked thrust thickening along the line of the Portsoy-Duchray Hill lineament and a new model for the metamorphism is proposed. The overprinting of andalusite-bearing assemblages by kyanite to the west of the Portsoy-Duchray Hill lineament is linked to pressure increases associated with the intrusion of the Newer Gabbros and represents a magmatic loading related to the same tectonothermal event that generated the low-pressure metamorphism, rather than a separate tectonic episode.
Key Words: metamorphism • lineaments • Rb/Sr • cooling • intrusions
This article has been cited by other articles:
 |
|
 |
|
  R. A. STRACHAN and J. A. EVANS Structural setting and U-Pb zircon geochronology of the Glen Scaddle Metagabbro: evidence for polyphase Scandian ductile deformation in the Caledonides of northern Scotland Geological Magazine, 2008; 145: 361 - 371. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L.M. Watts, R.E. Holdsworth, J.A. Sleight, R.A. Strachan, and S.A.F. Smith The movement history and fault rock evolution of a reactivated crustal-scale strike-slip fault: the Walls Boundary Fault Zone, Shetland Journal of the Geological Society, 2007; 164: 1037 - 1058. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
MichaelJ. Flowerdew, J.S. Daly, and MartinJ. Whitehouse 470 Ma granitoid magmatism associated with the Grampian Orogeny in the Slishwood Division, NW Ireland Journal of the Geological Society, 2005; 162: 563 - 575. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. M. Chew and D. M. CHEW Structural and stratigraphic relationships across the continuation of the Highland Boundary Fault in western Ireland Geological Magazine, 2003; 140: 73 - 85. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. A. Armstrong, H. A. ARMSTRONG, and A. W. OWEN Terrane evolution of the paratectonic Caledonides of northern Britain Journal of the Geological Society, 2001; 158: 475 - 486. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. J. Flowerdew, M. J. FLOWERDEW, J. S. DALY, P. G. GUISE, and D. C. REX Isotopic dating of overthrusting, collapse and related granitoid intrusion in the Grampian orogenic belt, northwestern Ireland Geological Magazine, 2000; 137: 419 - 435. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Fast tectonometamorphism and exhumation in the type area of the Barrovian and Buchan zones Geology, 2000; 28: 459 - 462.
|
|
|
|
 |
|
 B. J. Bluck Old Red Sandstone basins and alluvial systems of Midland Scotland Geological Society, London, Special Publications, 2000; 180: 417 - 437. [Abstract] [PDF]
|
|
|
|
|
|
P. W. G. TANNER and M. S. PRINGLE Testing for the presence of a terrane boundary within Neoproterozoic (Dalradian) to Cambrian siliceous turbidites at Callander, Perthshire, Scotland Journal of the Geological Society, 1999; 156: 1205 - 1216. [Abstract] [PDF]
|
|
|
|
|
|
N. J. SOPER, P. D. RYAN, and J. F. DEWEY Age of the Grampian orogeny in Scotland and Ireland Journal of the Geological Society, 1999; 156: 1231 - 1236. [Abstract] [PDF]
|
|
|
|
|
|
J. Dewey and M. Mange Petrography of Ordovician and Silurian sediments in the western Irish Caledonides: tracers of a short-lived Ordovician continent-arc collision orogeny and the evolution of the Laurentian Appalachian-Caledonian margin Geological Society, London, Special Publications, 1999; 164: 55 - 107. [Abstract] [PDF]
|
|
|
|
|
|
S. G. MOLYNEUX An upper Dalradian microfossil reassessed Journal of the Geological Society, 1998; 155: 741 - 743. [Abstract] [PDF]
|
|
|
|
|
|
G. ROGERS, E. K. HYSLOP, R. A. STRACHAN, B. A. PATERSON, and R. E. HOLDSWORTH The structural setting and U-Pb geochronology of Knoydartian pegmatites in W Inverness-shire: evidence for Neoproterozoic tectonothermal events in the Moineof NW Scotland Journal of the Geological Society, 1998; 155: 685 - 696. [Abstract] [PDF]
|
|
|
|
|
|
A. R. HUTCHISON and G. J. H. OLIVER Garnet provenance studies, juxtaposition of Laurentian marginal terranes and timing of the Grampian Orogeny in Scotland Journal of the Geological Society, 1998; 155: 541 - 550. [Abstract] [PDF]
|
|
|
|
|
|
J. A. Evans, J. A. Evans, N. J. Soper, T. J. Dempster, N. F. C. Hudson, and G. Rogers Discussion on metamorphism and cooling of the NE Dalradian * U-Pb and Rb-Sr geochronology of magmatism and metamorphism in the Dalradian of Connemara, western Ireland Journal of the Geological Society, 1997; 154: 357 - 360. [Abstract] [PDF]
|
|
