Editing Metalliferous mineral veins, Geology and man, Midland Valley of Scotland

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Many of the copper, lead and iron-bearing veins are associated with E–W fracture systems of post-Westphalian age and would seem to be part of the major Hercynian mineralisation episode of the British Isles. Several such veins are closely associated with quartz-dolerite intrusions and a Stephanian age is therefore indicated, in agreement with K-Ar dates on vein gouge clays from the Ochils of 300 to 280Ma.
 
Many of the copper, lead and iron-bearing veins are associated with E–W fracture systems of post-Westphalian age and would seem to be part of the major Hercynian mineralisation episode of the British Isles. Several such veins are closely associated with quartz-dolerite intrusions and a Stephanian age is therefore indicated, in agreement with K-Ar dates on vein gouge clays from the Ochils of 300 to 280Ma.
  
Baryte is a constituent of many of the Stephanian age veins but significantly most of the major baryte veins either occupy NW–SE fractures or occur within a 20 km-wide, NW–SE zone, coincident with the main Tertiary dyke swarm ([[Media:P915552.jpg|P915552]]). It has been suggested that this north-westerly control may indicate a Tertiary age for the mineralisation. However, it seems more likely that the Tertiary dykes occupy an older mineralised fracture system, possibly dating back to the Carboniferous. Unpublished radiometric dates from the Gasswater baryte deposit of 287 to 270 Ma suggest a late Carboniferous or Permian age, but the Muirshiel deposit is probably of Triassic age (240–213 Ma). Palaeomagnetic measurements on a baryte-hematite vein from Auchenstilloch point to a still younger Lower to Middle Jurassic age. It is possible that most of the Midland Valley baryte veins originated from an early Mesozoic cycle of magmatic and hydrothermal activity, recognised throughout NW Europe and probably related to the early opening of the North Atlantic.
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Baryte is a constituent of many of the Stephanian age veins but significantly most of the major baryte veins either occupy NW–SE fractures or occur within a 20 km-wide, NW–SE zone, coincident with the main Tertiary dyke swarm ([[Media:P915552.jpg|P915552]]). It has been suggested that this north-westerly control may indicate a Tertiary age for the mineralisation. However, it seems more likely that the Tertiary dykes occupy an older mineralised fracture system, possibly dating back to the Carboniferous. Unpublished radiometric dates from the Gasswater baryte deposit of 287 to 270Ma suggest a late Carboniferous or Permian age, but the Muirshiel deposit is probably of Triassic age (240–213 Ma). Palaeomagnetic measurements on a baryte-hematite vein from Auchenstilloch point to a still younger Lower to Middle Jurassic age. It is possible that most of the Midland Valley baryte veins originated from an early Mesozoic cycle of magmatic and hydrothermal activity, recognised throughout NW Europe and probably related to the early opening of the North Atlantic.  
 
 
 
== Bibliography ==
 
== Bibliography ==
 
Allen, P. M., Cooper, D. C., Parker, M. E., Easterbrook, G. D. and Haslam, H. W. 1982. Mineral exploration in the area of the Fore Burn igneous com­plex, south-western Scotland. Mineral Reconnaissance Programme, Rep. Inst. Geol. Sci., No. 55.
 
Allen, P. M., Cooper, D. C., Parker, M. E., Easterbrook, G. D. and Haslam, H. W. 1982. Mineral exploration in the area of the Fore Burn igneous com­plex, south-western Scotland. Mineral Reconnaissance Programme, Rep. Inst. Geol. Sci., No. 55.

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