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Hornblende-garnet metapyroxenite beneath serpentinite in the Ballantrae complex of SW Scotland and its bearing on the depth provenance of obducted oceanic lithosphere

Published online by Cambridge University Press:  03 November 2011

P. J. Treloar ,
B. J. Bluck ,
D. R. Bowes  and
Arnošt Dudek
P. J. Treloar
Affiliation:
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EW, England.
B. J. Bluck
Affiliation:
Department of Geology, University of Glasgow, Glasgow, G12 8QQ, Scotland.
D. R. Bowes
Affiliation:
Department of Geology, University of Glasgow, Glasgow, G12 8QQ, Scotland.
Arnošt Dudek
Affiliation:
Department of Geology, Charles University, Albertov 6, 128 43 Prague 2, Czechoslovakia.
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Abstract

Minimum T and P conditions for the crystallisation of banded amphibole (tschermakitic pargasite)-bearing garnet metapyroxenites that occur beneath and within a tectonically emplaced unit of serpentinite are 900±70°C and 10–11 (possibly 14–15) kb. This indicates both a depth provenance of at least 35–45 km for the obducted oceanic lithosphre which forms part of the ophiolite assemblage of the Ballantrae complex and also a palaeoheat-flow of at least 20°C/km. The metapyroxenites are interpreted as representing the products of subsolidus recrystallisation of a mantle accumulate pyroxenite. Together with associated amphibolites and epidote-rich mylonites formed at higher levels, they constitute a thin, transported and telescoped aureole made up of tectonic pieces of successively-formed metamorphic rocks that welded on to the base of an upward-moving and progressively-cooling peridotite slab.

Estimates of temperature of recrystallisation of the metapyroxenites were obtained using the garnet-pyroxene and garnet-amphibole exchange reactions as geothermometers. Estimates of pressure were obtained from assessments of the stability fields of the amphiboles, clinopyroxenes and garnets present and of the mineral assemblages in relation to published studies on the eclogite-granulite-amphibolite facies system.

Keywords

analysesArenigaureolebarometerclinopyroxeneheat-flowKnocklaughmicroprobeophiolitepyroxenitethermometertschermakitic pargasite55°11'N4°53'W
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 71 , Issue 4 , 1980 , pp. 201 - 212
Copyright
Copyright © Royal Society of Edinburgh 1980

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References

Balsillie, D. 1932. The Ballantrae Igneous Complex, South Ayrshire. GEOL MAG 69, 107–31.Google Scholar
Bloxam, T. W. & Allen, J. B. 1960. Glaucophane-schist, eclogite, and associated rocks from Knockormal in the Girvan-Ballantrae complex, South Ayrshire. TRANS R SOC EDINBURGH 64, 1–27.CrossRefGoogle Scholar
Bluck, B. J. 1978. Geology of a continental margin 1: the Ballantrae complex. In Bowes, D. R. & Leake, B. E. (eds) Crustal evolution in northwestern Britain and adjacent regions, 151–62. GEOL J SPEC ISSUE 10.Google Scholar
Bluck, B. J., Halliday, A. N., Aftalion, M. & Macintyre, R. M. 1980. Age and origin of Ballantrae ophiolite, its significance to Caledonian orogeny and Ordovician time-scale. GEOLOGY 8, 492–5.Google Scholar
Boyd, F. R. 1959. Hydrothermal investigations of amphiboles. In Abelson, P. H. (ed.) Researches in Geochemistry, 377–96. New York: John Wiley & Sons.Google Scholar
Charlu, T. V., Newton, R. C. & Kleppa, O. J. 1975. Enthalpies of formation at 970 K of compounds in the system MgO-Al2O3-SiO2 from high temperature solution calorimetry. GEOCHIM COSMOCHIM ACTA 39, 1487–97.Google Scholar
Charlu, T. V., Newton, R. C. & Kleppa, O. J. 1978. Enthalpy of formation of some lime silicates by high-temperature solution calorimetry, with discussion of high pressure phase equilibria. GEOCHIM COSMOCHIM ACTA 42, 367–75.Google Scholar
Church, W. R. & Gayer, R. A. 1973. The Ballantrae ophiolite. GEOL MAG 110, 497–510.CrossRefGoogle Scholar
Cressey, G., Schmid, R. & Wood, B. J. 1978. Thermodynamic properties of almandine-grossular garnet solid solutions. CONTRIB MINERAL PETROL 67, 397–404.CrossRefGoogle Scholar
Ellis, D. J. & Green, D. H. 1979. An experimental study of the effect of Ca upon garnet-clinopyroxene Fe-Mg exchange equilibria. CONTRIB MINERAL PETROL 71, 13–22.Google Scholar
Essene, E. J., Hensen, B. J. & Green, D. H. 1970. Experimental study of amphibolite and eclogite stability. PHYS EARTH PLANET INTER 3, 378–84.CrossRefGoogle Scholar
Gilbert, M. C. 1966. Synthesis and stability relations of hornblende ferropargasite. AM J SCI 264, 698–742.CrossRefGoogle Scholar
Gilbert, M. C. 1968. Reconnaissance study of the stability of amphiboles at high pressure. CARNEGIE INST WASHINGTON YEARBOOK 67, 167–70.Google Scholar
Graham, C. M. & England, P. C. 1976. Thermal regimes and regional metamorphism in the vicinity of overthrust faults: an example of shear heating and inverted metamorphic zonation from southern California. EARTH PLANET SCI LETT 31, 142–52.CrossRefGoogle Scholar
Green, D. H. 1966. The origin of the “eclogites” from Salt Lake Crater, Hawaii. EARTH PLANET SCI LETT 1, 414–20.Google Scholar
Green, D. H. & Ringwood, A. E. 1967. An experimental investigation of the gabbro to eclogite transformation and its petrological applications. GEOCHIM COSMOCHIM ACTA 31, 767–833.Google Scholar
Harte, B. 1977. Rock nomenclature with particular relation to deformation and recrystallisation textures in olivine-bearing xenohths. J GEOL 85, 279–88.Google Scholar
Helgeson, H. C., Delany, J. M., Nesbitt, H. W. & Bird, D. K. 1978. Summary and critique of the thermodynamic properties of rock-forming minerals. AM J SCI 278–A.Google Scholar
Hensen, B. J. 1976. The stability of pyrope-grossular garnet with excess silica. CONTRIB MINERAL PETROL 55, 279–92.CrossRefGoogle Scholar
Henson, B. J., Schmid, R. & Wood, B. J. 1975. Activity-composition relationships for pyrope-grossular garnet. CONTRIB MINERAL PETROL 51, 161–6.Google Scholar
Hobbs, B. E., Means, W. D. & Williams, P. F. 1976, An Outline of Structural Geology. New York: John Wiley & Sons.Google Scholar
Irving, A. J. 1974. Geochemical and high pressure experimental studies of garnet pyroxenite and pyroxene granulite xenoliths from the Delegate basaltic pipes, Australia. J PETROL 15, 1–40.Google Scholar
Jelínek, E., Souček, J., Bluck, B. J., Bowes, D. R. & Treloar, P. J. 1980. Nature and significance of beerbachites in the Ballantre ophiolite, SW Scotland. TRANS R SOC EDINBURGH 71, 159–179.Google Scholar
Kushiro, I. 1969. Clinopyroxene solid solutions formed by reactions between diopside and plagioclase at high pressures. MINERAL SOC AM SPEC PAP 2, 179–91.Google Scholar
Longman, C. D., Bluck, B. J. & van Breemen, O. 1979. Ordovician conglomerates and evolution of the Midland Valley. NATURE 280, 578–81.CrossRefGoogle Scholar
Lovering, J. F. & White, A. J. R. 1969. Granulitic and eclogitic inclusions from basic pipes at Delegate, Australia. CONTRIB MINERAL PETROL 21, 9–52.Google Scholar
Malpas, J. 1979. The dynamothermal aureole of the Bay of Islands ophiolite suite. CAN J EARTH SCI 16, 2086–101.Google Scholar
Newton, R. C., Charlu, T. V. & Kleppa, O. J. 1977. Thermochemistry of high pressure garnets and clinopyroxenes in the system CaO-MgO-Al2O3-SiO2. GEOCHIM COSMOCHIM ACTA 41, 369–77.Google Scholar
Omaston, M. F. 1979. In discussion of Barber, A. J. & Max, M. D. A new look at the Mona Complex (Anglesey, North Wales). J GEOL SOC LONDON 136, 430–1.Google Scholar
Papike, J. J., Cameron, K. L. & Baldwin, K. 1974. Amphiboles and pyroxenes: characterization of other than quadrilateral components and estimates of ferric iron from microprobe data. GEOL SOC AM ABSTR WITH PROGRAMS 6, 1053–4.Google Scholar
Peach, B. N. & Horne, J. 1899. The Silurian rocks of Great Britain 1. Scotland. MEM GEOL SURV U K.Google Scholar
Robie, R. A. & Waldbaum, D. R. 1968. Thermodynamicproperties of minerals and related substances at 298·15 K (25·0°C) and one atmosphere (1·013 bars) pressure and at higher temperatures. US GEOL SURV BULL 1259, 256 pp.Google Scholar
Searle, M. P. & Malpas, J. 1980. Structure and metamorphism of rocks beneath the Semail ophiolite of Oman and their significance in ophiolite obduction. TRANS R SOC EDINBURGH EARTH SCI 71, 247–62.Google Scholar
Spray, J. G. and Williams, G. D. 1980. The sub-ophiolite metamorphic rocks of the Ballantrae Igneous Complex, SW Scotland. J GEOL SOC LONDON 137, 359–68.CrossRefGoogle Scholar
Spry, A. 1969. Metamorphic Textures. Oxford: Pergamon Press.Google Scholar
Vernon, R. H. 1976. Metamorphic Processes Reactions and Micro-structure Development. London: Allen & Unwin.Google Scholar
Watanabe, T., Langseth, M. G. & Anderson, R. N. 1977. Heat flow in back-arc basins of the Western Pacific. In Talwani, M. & Pittman, W. C. (eds) Island arcs and deep sea trenches and back-arc basins, 137–61. AM GEOPHYS UNION MAURICE EWING SER 1.Google Scholar
Wells, P. R. A. 1979a. Chemical and thermal evolution of Archaean sialic crust, southern West Greenland. J PETROL 20, 187–226.Google Scholar
Wells, P. R. A. 1979b. P–T conditions in the Moines of the Central Highlands, Scotland. J GEOL SOC LONDON 136, 663–71.CrossRefGoogle Scholar
White, A. J. R. 1964. Clinopyroxenes from eclogites and basic granulites. AM MINERAL 49, 883–8.Google Scholar
Wilkinson, J. F. G. 1974. Garnet clinopyroxenite inclusions from diatremes in the Gloucester area, New South Wales, Australia. CONTRIB MINERAL PETROL 46, 275–99.Google Scholar
Williams, A. 1959. A structural history of the Girvan district, S.W. Ayrshire. TRANS R SOC EDINBURGH 63, 629–67.Google Scholar
Williams, H. & Smyth, W. R. 1973. Metamorphic aureoles beneath ophiolite suites and alpine peridotites: tectonic implications with West Newfoundland examples. AM J SCI 273, 594–621.Google Scholar