Hostname: page-component-cd9895bd7-dzt6s Total loading time: 0 Render date: 2024-12-23T15:45:17.216Z Has data issue: false hasContentIssue false
  • English
  • Français

Emplacement and thermal metamorphism associated with the post-orogenic Strath Ossian Pluton, Grampian Highlands, Scotland

Published online by Cambridge University Press:  01 May 2009

R. M. Key ,
E. R. Phillips  and
B. C. Chacksfield
R. M. Key
Affiliation:
British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, U.K.
E. R. Phillips
Affiliation:
British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, U.K.
B. C. Chacksfield
Affiliation:
British Geological Survey, Keyworth, Nottingham NG12 5GG, U.K.
Get access Rights & Permissions [Opens in a new window]

Abstract

The multiphase Strath Ossian Pluton was intruded into metasedimentary rocks of the Neoproterozoic Grampian and Appin groups (Grampian Highlands, Scotland) during Silurian or early Devonian times. Emplacementfollowed the main ductile tectono-thermal history of the area and took place during post-orogenic regional uplift and cooling. Early emplacement of dioritic magma in the northern part of the pluton resulted in migmatization of its immediate country rocks with the generation of new ductile structures. The main granodiorite was then emplaced with magma migrating towards the southeast where wall-rock stoping took place. Elsewhere the pluton created its own space with little stoping or veining. Thermal metamorphism caused by granodiorite emplacement resulted in the progressive development of the assemblage quartz+ plagioclase + biotite+ cordierite +andalusite ± K-feldspar in the metapelitic country rocks. Six prograde mineral assemblage zones are identified in the aureole. Final emplacement of a marginal porphyritic microgranite was accompanied by the release of alkaline fluids into the thermal aureole. This produced sillimanite (fibrolite) in association with hydrous phases such as chlorite and white mica. The development of andalusite and cordierite-bearing assemblages is estimated to have occurred at temperatures of 650±50 °C at an estimated pressure of 3.2±0.5 kbars. An approximately isobaric temperature change of 300±50 °C across the width of the main aureole is deduced. The migmatization close to the plutons margins took place at temperatures of about 700 °C. An estimated depth of emplacement of about 11 km is obtained for the Strath Ossian Pluton. This implies considerable regional uplift both prior to, andimmediately after its emplacement. Thus it has been estimated that at the peak of regional metamorphism, probably during the Ordovician Period, the country rocks were at a depth of 15 to 18.5 km, whereas the early Devonian dykes of the Etive dyke swarm, which cut the Strath Ossian Pluton, were emplaced at, or near surface.

Type
Articles
Information
Geological Magazine , Volume 130 , Issue 3 , May 1993 , pp. 379 - 390
Copyright
Copyright © Cambridge University Press 1993

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Anderson, J. G. C. 1956. The Moinian Dalradian rocks between Glen Roy and the Monadhliath Mountains, Inverness-shire. Transactions of the Royal Society, Edinburgh 63, 15–36.Google Scholar
Bailey, E. G. & Maufe, H. B. 1960. The geology of Ben Nevis and GlenCoe and the surrounding Country: Explanation of Sheet 53. Memoir of theGeological Survey of Scotland, HMSO, Edinburgh.Google Scholar
Brown, W. L. & Parsons, I. 1981. Towards a more practical two-feldspar geothermometer. Contributions to Mineralogy and Petrology 76, 369–77.CrossRefGoogle Scholar
Clayburn, J. A. P., Harmon, R. S., Pankhurst, R. J. & Brown, J. F. 1983. Sr, O, and Pb isotope evidence for origin and evolution of Etive Igneous Complex, Scotland. Nature 303, 492–7.CrossRefGoogle Scholar
Droop, G. T. R. & Treloar, P. J. 1981. Pressure of metamorphism in the aureole of the Etive Granite Complex. Scottish Journal of Geology 17, 85–102.CrossRefGoogle Scholar
Hanson, G. N. & Gast, P. W. 1967. Kinetic studies in contact metamorphic zones. Geochemica Cosmochimica Acta 31, 1119–53.CrossRefGoogle Scholar
Harmon, R. S. 1983. Oxygen and strontium evidence regarding the role of continental crust in the origin and evolution of the British Caledonian granites. In Migmatites, Melting and Metamorphism (eds Atherton, M. P. and Gribble, C. D.), pp. 62–79. Nantwich, Cheshire: Shiva.Google Scholar
Harrison, T. N. 1986. The method of emplacement of the Cairngorm granite. Scottish Journal of Geology 22, 303–14.CrossRefGoogle Scholar
Haselton, H. T. Jr, Hovis, G. L., Hemingway, B. S. & Robie, R. A. 1983. Calorimetric investigation of the excess entropy of mixing in albite-sanadine solid solutions: lack of evidence for Na, K short-range order and implications for two-feldspar thermometry. American Mineralogist 68, 398–413.Google Scholar
Henderson, W. G. 1982. Geology of the northern part of the Strath Ossian Granite, Scotland. Report of the Institute of Geological Society ENPU 82–16, 22.Google Scholar
Hinxman, L. W., Carruthers, R. G. & MacGregor, M. 1923. The geology of Corrour and the Moor of Rannoch. Memoir of the Geological Survey of Scotland no. 54, 96 pp.Google Scholar
Holland, T. J. B. & Powell, R. 1990. An enlarged and updated internallyconsistent thermodynamic data set with uncertainties and correlations: the system K2O-Na2O-CaO-MgO-FeO-Fe2O3 Al2O3-TiO2- SiO2-C-H2-O2. Journal of Metamorphic Geology 8, 89–124.CrossRefGoogle Scholar
Kerrick, D. M. 1987. Fibrolite in contact aureoles of Donegal, Ireland. American Mineralogist 72, 240–50.Google Scholar
Key, R. M., May, F. & Phillips, E. R. 1991. Progressive deformation in part of the south-western Scottish Caledonides. Terra Abstracts 3, 20/1.Google Scholar
Pattison, D. R. M. 1989. P-T conditions and the influence of graphite on pelitic phase relationships in the Ballachulish Aureole, Scotland. Journalof Petrology 30, 1219–44.CrossRefGoogle Scholar
Pattison, D. R. M. & Harte, B. 1985. A petrogenetic grid for pelites inthe Ballachulish and other Scottish thermal aureoles. Journal of the Geological Society 142, 7–28.CrossRefGoogle Scholar
Pattison, D. R. M. & Harte, B. 1988. Evolution of structurally contrasting anatectic migmatites in the 3–kbar Ballachulish aureole, Scotland. Journal of Metamorphic Geology 6, 475–94.CrossRefGoogle Scholar
Phillips, E. R. 1991. Metamorphic history and microfabric analysis of the Appin Group pelitic schists, southern sheet 63 W. British Geological Survey, Technical Report WG/91/34.Google Scholar
Pidgeon, R. T. & Aftalion, M. 1978. Cogenetic vs inherited zircon U-Pb systems in granites: Palaeozoic granites of Scotland and England. In Crustal evolution of north-west Britain and adjacent regions (eds Bowes, D. E. and Leake, B. E.), pp. 183–220. Geological Journal, Special Issue no. 10.Google Scholar
Pitcher, W. S. 1982. Granite type and tectonic environment. In Mountain Building Processes (ed. Hsu, K. J.), pp. 19–40. London Academic Press.Google Scholar
Plant, J. A. 1986. Models for granites and their mineralising systems in the British and Irish Caledonides. In Geology and genesis of mineral deposits in Ireland (ed. Andrew, C. J.), pp. 121–56. Irish Association for Economic Geology, Dublin.CrossRefGoogle Scholar
Powell, R. & Evans, J. A. 1983. A new geobarometer for the assemblage biotite-muscovite-chlorite-quartz. Journal of Metamorphic Geology 1, 331–6.CrossRefGoogle Scholar
Read, H. H. 1961. Aspects of Caledonian magmatism in Britain. Liverpool and Manchester Geological Journal 2, 653–83.CrossRefGoogle Scholar
Richardson, S. W. & Powell, R. 1976. Thermal causes of Dalradian metamorphism in the Central Highlands of Scotland. Scottish Journal of Geology 12, 237–68.CrossRefGoogle Scholar
Stevens, W. E. & Halliday, A. M. 1984. Geochemical contrasts between late Caledonian plutons of northern, central and southern Scotland. Transactions of the Royal Society Edinburgh, Earth Sciences 75, 259–73.CrossRefGoogle Scholar
Stormer, J. C. Jr 1975. A practical two-feldspar geothermometer. American Mineralogist 60, 667–74.Google Scholar
Stormer, J. C. Jr & Whitney, J. A. 1977. Two-feldspar geothermometry in granulite facies metamorphic rocks: sapphrine granulites from Brazil. Contributions to Mineralogy and Petrology 65, 123–33.CrossRefGoogle Scholar
Thirlwall, M. F. 1988. Geochronology of Late Caledonian magmatism in northern Britain. Journal of the Geological Society 145, 951–68.CrossRefGoogle Scholar
Tyler, L. M. & Asxworth, J. R. 1983. The metamorphic environment of theFoyers Granite complex. Scottish Journal of Geology 19, 271–85.CrossRefGoogle Scholar
Watson, J. V. 1984. The ending of the Caledonian orogeny in Scotland. Journal of the Geological Society 141, 193–214.CrossRefGoogle Scholar
Wells, P. R. A. 1979. P-T conditions in the Moines of the Central Highlands, Scotland. Journal of the Geological Society 136, 663–71.CrossRefGoogle Scholar