Hostname: page-component-cd9895bd7-7cvxr Total loading time: 0 Render date: 2024-12-23T20:23:19.624Z Has data issue: false hasContentIssue false
  • English
  • Français

The distribution of metamorphic temperatures around the Strontian Granodiorite

Published online by Cambridge University Press:  01 May 2009

J. R. Ashworth  and
I. M. Tyler
J. R. Ashworth
Affiliation:
Department of Geological Sciences, University of Aston in Birmingham, Gosta Green, Birmingham B4 7ET
I. M. Tyler
Affiliation:
Department of Geological Sciences, University of Aston in Birmingham, Gosta Green, Birmingham B4 7ET
Get access Rights & Permissions [Opens in a new window]

Summary

The Strontian Granodiorite, a ‘Newer Granite’ emplaced late in the Caledonian orogenic cycle, has an aureole which is strongly asymmetrical: the metamorphic zones are broader to the east of the intrusion than to the west. The asymmetry is attributed to a gradient in the background, regional temperatures. The muscovite-out isograd, marking completion of dehydration of muscovite + quartz to sillimanite + K feldspar (estimated temperature 645 °C), lies within 2 km of the contact on the west, whereas the cordierite isograd, due to the onset of dehydration of biotite+sillimanite+quartz (estimated temperature 690 °C) is at least 2.5 km from the contact on the east. This temperature interval of 45 °C, which is rather insensitive to small errors in the estimated pressure (preferred value 4.1 kbar), is used in a simple geometrical treatment to estimate the regional gradient in the plane of present exposure: approximately 5 °C/km in a direction 30° S of E. Because the intrusion does not appear to have been tilted, this result is regarded as an estimate of the horizontal component of the temperature gradient on the west flank of a regional thermal dome, inherited from the regional metamorphic climax and decaying on a timescale which is suggested, by radiometric data in the literature, to be ˜ 10 Ma. A tectonic origin for the perturbed regional temperature distribution (uplift of hot rocks in the east relative to colder rocks further west) is suggested by the metamorphic petrology of the region, and supported by literature data on structural movements, notably of the Sgurr Beag Slide.

Type
Articles
Information
Geological Magazine , Volume 120 , Issue 3 , May 1983 , pp. 281 - 290
Copyright
Copyright © Cambridge University Press 1983

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

REFERENCES

Ashworth, J. R. & Chinner, G. A. 1978. Coexisting garnet and cordierite in migmatites from the Scottish Caledonides. Contrib. Mineral. Petrol. 65, 379–94.CrossRefGoogle Scholar
Atherton, M. P. 1977. The metamorphism of the Dairadian rocks of Scotland. Scott. J. Geol.. 13, 331–70.CrossRefGoogle Scholar
Borradaile, G. J. (1976). Thermal anisotropy - a factor contributing to the distribution of Caledonian metamorphic zones in the SW Scottish Highlands? Geologie Mijnb. 55, 41–5.Google Scholar
Brewer, M. S., Brook, M. & Powell, D. 1979. Dating of the tectono-metamorphic history of the southwestern Moine, Scotland. In The Caledonides of the British Isles - Reviewed (ed. Harris, A. L., Holland, C. H. & Leake, B. E.), pp. 129–37. Geol. Soc. Lond. Spec. Publ. 8.Google Scholar
Chatterjee, N. D. & Johannes, W. 1974. Thermal stability and standard thermodynamic properties of synthetic 2M1-muscovite, KAl2[AlSi3O10(OH)2]. Contrib. Mineral. Petrol. 48, 89–114.CrossRefGoogle Scholar
Dearnley, R. 1967. Metamorphism of minor intrusions associated with the Newer Granites of the Western Highlands of Scotland. Scott. J. Geol. 3, 449–57.CrossRefGoogle Scholar
Dewey, J. F. & Pankhurst, R. J. 1970. The evolution of the Scottish Caledonides in relation to their isotopic age pattern. Trans. R. Soc. Edinb. 68, 361–89.Google Scholar
Drever, H. I. 1940. The geology of Ardgour, Argyllshire. Trans. R. Soc. Edinb. 60, 141–70.Google Scholar
Halliday, A. N., Aftalion, M., van Breemen, O. & Jocelyn, J. 1979. Petrogenetic significance of Rb-Sr and U-Pb isotopic systems in the 400 Ma old British Isles granitoids and their hosts. In The Caledonides of the British Isles - Reviewed (ed. Harris, A. L., Holland, C. H. and Leake, B. E.), pp. 653–61. Geol. Soc. Lond. Spec. Publ. 8.Google Scholar
Hamilton, P. J., O’Nions, R. K. & Pankhurst, R. J. 1980. Isotopic evidence for the provenance of some Caledonian granites. Nature 287, 279–84.CrossRefGoogle Scholar
Harry, W. T. 1954. The composite granitic gneiss of western Ardgour, Argyll, Q. Jl geol. Soc. Lond. 109, 285–309.CrossRefGoogle Scholar
Holdaway, M. J. & Lee, S. M. 1977. Fe-Mg cordierite stability in high-grade pelitic rocks based on experimental, theoretical and natural observations. Contrib. Mineral. Petrol. 63, 175–98.CrossRefGoogle Scholar
Holder, M. T. 1979. An emplacement mechanism for post-tectonic granites and its implications for their geochemical features. In Origin of Granite Batholiths (ed. Atherton, M. P. and J., Tarney), pp. 116–28. Orpington: Shiva.CrossRefGoogle Scholar
Jaeger, J. C. 1959. Temperatures outside a cooling intrusive sheet. Am. J. Sci. 257, 44–54.CrossRefGoogle Scholar
Lambert, R. St J., Winchester, J. A. & Holland, J. G. 1979. Time, space and intensity relationships of the Precambrian and Lower Palaeozoic metamorphisms of the Scottish Highlands. In The Caledonides of the British Isles - Reviewed (ed. Harris, A. L., Holland, C. H. and Leake, B. E.), pp. 363–67. Geol. Soc. Lond. Spec. Publ. 8.Google Scholar
Munro, M. 1965. Some structural features of the Caledonian granitic complex at Strontian, Argylishire. Scott. J. Geol. 1, 152–75.CrossRefGoogle Scholar
Munro, M. 1973. Structures in the south-eastern portion of the Strontian granitic complex, Argyllshire. Scott. J. Geol. 9, 99–108.CrossRefGoogle Scholar
Ohmoto, H. & Kerrick, D. 1977. Devolatilization equilibria in graphitic systems. Am. J. Sci. 277, 1013–44.CrossRefGoogle Scholar
Pidgeon, R. T. & Aftalion, M. 1978. Cogenetic and inherited zircon U-Pb systems in granites: Palaeozoic granites of Scotland and England. In Crustal Evolution in Northwestern Britain and Adjacent Regions (ed. Bowes, D. R. and Leake, B. E.), pp. 183–220. Geol. J. Special Issue 10.Google Scholar
Powell, D. 1974. Stratigraphy and structure of the western Moine and the problem of Moine orogenesis. Ji geol. Soc. Lond. 130, 575–93.CrossRefGoogle Scholar
Powell, D., Baird, A. W., Charnley, N. R. & Jordan, P. J. 1981. The metamorphic environment of the Sgurr Beag Slide; a major crustal displacement zone in Proterozoic, Moine rocks of Scotland. Jl geol. Soc. Lond. 138, 661–73.CrossRefGoogle Scholar
Sabine, P. A. 1963. The Strontian granite complex, Argyllshire. Bull. geol. Surv. Gt Br. 20, 6–42.Google Scholar
Smith, D. I. 1979. Caledonian minor intrusions of the N Highlands of Scotland. In The Caledonides of the British Isles - Reviewed (ed. Harris, A. L., Holland, C. H. & Leake, B. E.), pp. 683–97. Geol. Soc. Lond. Spec. Publ. 8.Google Scholar
Tanner, P. W. G., Johnstone, G. S., Smith, D. I. & Harris, A. L. 1970. Moinian stratigraphy and the problem of the central Ross-shire inliers. Bull. geol. Soc. Am. 81, 299–306.CrossRefGoogle Scholar
Turner, F. J. 1981. Metamorphic Petrology: Mineralogical, Field and Tectonic Aspects, 2nd ed. New York: McGraw-Hill.Google Scholar
Tyler, I. M. & Ashworth, J. R. 1981. Garnet zoning and re-equilibration in the Strontian area, Scotland. Mineralog. Mag. 44, 293–300.CrossRefGoogle Scholar
Tyler, I. M. & Ashworth, J. R. 1982. Sillimanite-potash feldspar assemblages in graphite pelites, Strontian area, Scotland, Contrib. Mineral. Petrol. (in the Press).CrossRefGoogle Scholar
van Breemen, O., Aftalion, M., Pankhurst, R. J. & Richardson, S. W. 1979. Age of the Glen Dessary Syenite, Inverness-shire: diachronous Palaeozoic metamorphism across the Great Glen. Scott. J. Geol. 15, 49–62.CrossRefGoogle Scholar
Watson, J. V. 1964. Conditions in the metamorphic Caledonides during the period of late-orogenic cooling. Geol. Mag. 101, 457–65.CrossRefGoogle Scholar
Winchester, J. A. 1974. The zonal pattern of regional metamorphism in the Scottish Caledonides. Jl geol. Soc. Lond. 130, 509–24.CrossRefGoogle Scholar