Hostname: page-component-848d4c4894-pftt2 Total loading time: 0 Render date: 2024-05-22T16:53:18.849Z Has data issue: false hasContentIssue false
  • English
  • Français

Isotope, trace element and major element geochemistry of Tertiary igneous rocks, Isle of Arran, Scotland

Published online by Cambridge University Press:  03 November 2011

A. P. Dickin ,
S. Moorbath  and
H. J. Welke
A. P. Dickin
Affiliation:
Department of Geology and Mineralogy, University of Oxford, Parks Road, Oxford OX1 3PR, England (A.P.D. now at Isotope Geology Unit, Scottish Universities Research and Reactor Centre, East Kilbride, Glasgow G75 OQU, Scotland).
S. Moorbath
Affiliation:
Department of Geology and Mineralogy, University of Oxford, Parks Road, Oxford OX1 3PR, England (A.P.D. now at Isotope Geology Unit, Scottish Universities Research and Reactor Centre, East Kilbride, Glasgow G75 OQU, Scotland).
H. J. Welke
Affiliation:
Bernard Price Institute of Geophysical Research, University of the Witwatersrand, Johannesburg 2001, South Africa.
Get access Rights & Permissions [Opens in a new window]

Abstract

Pb- and Sr-isotope, major element and trace element analyses are presented for 38 Tertiary igneous rocks and older country rocks from Arran. Tertiary igneous rocks define silica-undersaturated and -oversaturated differentiation trends, but acidic and basic examples of the latter trend, exemplified in composite dykes, are separated by a wide Daly gap. In contrast, Pb-, and to some extent Sr-isotope compositions of these rocks display continuous variation, almost independent of major element composition.

Isotopic variations are interpreted as resulting principally from crustal contamination of the differentiation products of mantle-derived basic magma. A dominant rôle by mantle heterogeneity or crustal anatexis in producing the isotopic variation is ruled out. Contamination is believed to have occurred primarily after differentiation, but some rocks, such as the fine unit of the Northern Granite, display evidence of post-contamination differentiation.

Tertiary igneous rocks define an array on a Pb/Pb isochron diagram whose slope corresponds to an apparent age of 770±180 Ma (2σ). This points to the existence of a late Proterozoic basement complex under Arran.

Acidic and basic members of composite dykes are interpreted as basaltic differentiates which have been variably affected by contamination, yielding wide ranges of isotopic composition. Composite intrusion is ascribed to the simultaneous presence of acidic and basic magma in the crust.

Keywords

apparent agebasaltic differentiationcomposite dykecrustal contaminationgraniteisochronmagmamantlePb isotopesProterozoicSr isotopes.
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 72 , Issue 3 , 1981 , pp. 159 - 170
Copyright
Copyright © Royal Society of Edinburgh 1981

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. 1947. The geology of the Highland Border; Stonehaven to Arran. TRANS R SOC EDINBURGH 61, 479–515.CrossRefGoogle Scholar
Arden, J. W. & Gale, N. H. 1974. New electrochemical technique for the separation of lead at trace levels from natural silicates. ANAL CHEM 46, 2–9.CrossRefGoogle Scholar
Bamford, D., Nunn, K., Prodehl, C. & Jacobs, B. 1977. LISPB-III. Upper crustal structure of northern Britain. J GEOL SOC LONDON 133, 481–8.CrossRefGoogle Scholar
Bamford, D. & Prodehl, C. 1977. Explosion seismology and the continental crust-mantle boundary. J GEOL SOC LONDON 134, 139–51.CrossRefGoogle Scholar
Beckinsale, R. D., Pankhurst, R. J., Skelhorn, R. R. & Walsh, J. N. 1978. Geochemistry and petrogenesis of the early Tertiary lava pile of the Isle of Mull, Scotland. CONTRIB MINERAL PETROL 66, 415–27.CrossRefGoogle Scholar
Bowes, D. R. 1968. The absolute time scale and the subdivision of Precambrian rocks in Scotland. GEOL FÖREN FÖRH STOCKHOLM 90, 175–88.CrossRefGoogle Scholar
Brooks, C. & Hart, S. R. 1978. Rb-Sr mantle isochrons and variations in the chemistry of Gondwanaland's lithosphere. NATURE 271, 220–3.CrossRefGoogle Scholar
Brooks, C., James, D. E. & Hart, S. R. 1976. Ancient lithosphere: its role in young continental volcanism. SCIENCE 183, 1086–94.CrossRefGoogle Scholar
Chapman, H. J. 1978. Geochronology and isotope geochemistry of Precambrian rocks from Northwest Scotland. Unpublished D.Phil. Thesis, Oxford University.Google Scholar
Chapman, H. J. & Moorbath, S. 1977. Lead isotope measurements from the oldest recognised Lewisian gneisses of north-west Scotland. NATURE 268, 41–2.CrossRefGoogle Scholar
Cohen, R. S., Evensen, N. M., Hamilton, P. J. & O'Nions, R. K. 1980. U-Pb, Sm-Nd and Rb-Sr systematics of mid-ocean ridge basalt glasses. NATURE 283, 149–53.CrossRefGoogle Scholar
Dickin, A. P. 1981. Isotope geochemistry of Tertiary igneous rocks from the Isle of Skye N.W. Scotland. J PETROL 22, 159–89.CrossRefGoogle Scholar
Dickin, A. P. & Exley, R. A. 1981. Isotopic and geochemical evidence for magma mixing in the petrogenesis of the Coire Uaigneich Granophyre, Isle of Skye N.W. Scotland. CONTRIB MINERAL PETROL 76, 98–108.CrossRefGoogle Scholar
Dickin, A. P., Exley, R. A. & Smith, B. M. 1980. Isotopic measurement of Sr and O exchange between meteoric-hydrothermal fluid and the Coire Uaigneich Granophyre, Isle of Skye N.W. Scotland. EARTH PLANET SCI LETT 51, 58–70.CrossRefGoogle Scholar
Dupré, B. & Allègre, C. J. 1980. Pb-Sr-Nd isotopic correlation and the chemistry of the North Atlantic mantle. NATURE 286, 17–22.CrossRefGoogle Scholar
Evans, A. L., Fitch, F. J. & Miller, J. A. 1973. Potassium-argon age determinations on some British Tertiary igneous rocks. J GEOL SOC LONDON 129, 419–43.CrossRefGoogle Scholar
Flanagan, F. J. 1973. 1972 values for international geochemical reference samples. GEOCHIM COSMOCHIM ACTA 37, 1189–200.CrossRefGoogle Scholar
Gale, N. H. 1967. Development of the delayed neutron technique as a rapid and precise method for determination of uranium and thorium at trace levels in rocks and minerals, with applications to isotope geochronology. In: Radioactive dating and methods of low-level counting, 431–53. Vienna: International Atomic Energy Agency.Google Scholar
Gibb, F. G. F. & Henderson, C. M. B. 1978. The petrology of the Dippin sill, Isle of Arran, SCOTT J GEOL 14, 1–27.CrossRefGoogle Scholar
Graham, A. M. & Upton, B. G. J. 1978. Gneisses in diatremes, Scottish Midland Valley: petrology and tectonic implications. J GEOL SOC LONDON 135, 219–28.CrossRefGoogle Scholar
Hall, J. 1978. ‘Lust’—a seismic refraction survey of the Lewisian basement complex in N.W. Scotland. J GEOL SOC LONDON 135, 555–63.CrossRefGoogle Scholar
Henderson, C. M. B. & Gibb, F. G. F. 1977. Formation of analcime in the Dippin sill, Isle of Arran. MINERAL MAG 41, 534–7.CrossRefGoogle Scholar
Jaffey, A. H., Flynn, K. F., Glendenin, L. E., Bentley, W. C. & Essling, A. M. 1971. Precision measurements of half-lives and specific activities of 235U and 238U. PHYS REV C4, 1889–906.Google Scholar
Johnson, T. P. & Meighan, I. G. 1975. The Northern Granite Complex, Isle of Arran. J GEOL SOC LONDON 131, 331.Google Scholar
Judd, J. W. 1893. On composite dykes in Arran. Q J GEOL SOC LONDON 49, 536–65.CrossRefGoogle Scholar
Lambert, R. St J. & Holland, J. G. 1972. A geochronological study of the Lewisian from Loch Laxford to Durness, Sutherland, N. W. Scotland. J GEOL SOC LONDON 128, 3–19.CrossRefGoogle Scholar
Le Roux, L. J. & Glendenin, L. E. 1963. Half-life of thorium 232. PROC NATL CONF NUCL ENERGY, PRETORIA, 82–94.Google Scholar
Macgregor, M., Herriot, A. & King, B. C. 1965. Excursion Guide to the Geology of Arran. Glasgow: Geological Society of Glasgow.Google Scholar
Macintyre, R. M., McMenamin, T. & Preston, J. 1975. K-Ar results from Western Ireland and their bearing on the timing and siting of Thulean magmatism. SCOTT J GEOL 11, 227–49.CrossRefGoogle Scholar
Meighan, I. G. 1979. The acid igneous rocks of the British Tertiary Province. BULL GEOL SURV GB 70, 10–22.Google Scholar
Moorbath, S. & Taylor, P. N. 1981. Isotopic evidence for continental growth in the Precambrian. In Kröner, A. (ed.) Precambrian Plate Tectonics, 491–525. Amsterdam: Elsevier.Google Scholar
Moorbath, S. & Thompson, R. N. 1980. Strontium isotope geochemistry and petrogenesis of the early Tertiary lava pile of the Isle of Skye, Scotland, and other basic rocks of the British Tertiary Province: an example of magma-crust interaction. J PETROL 21, 295–321.CrossRefGoogle Scholar
O'Nions, R. K., Hamilton, P. J. & Hooker, P. J. 1981. The evolution of sedimentary rocks: Nd-isotope study of Archaean to recent sediments. TERRA COGNITA SPEC ISSUE, 82.Google Scholar
O'Nions, R. K. & Pankhurst, R. J. 1973. Secular variation in the Sr-isotope composition of Icelandic volcanic rocks. EARTH PLANET SCI LETT 21, 13–21.CrossRefGoogle Scholar
Oversby, V. M. 1974. New look at the lead isotope growth curve. NATURE 248, 132–3.CrossRefGoogle Scholar
Pankhurst, R. J. 1977. Strontium isotope evidence for mantle events in the continental lithosphere. J GEOL SOC LONDON 134, 255–68.CrossRefGoogle Scholar
Rogers, J. J. W. & Adams, J. A. S. 1978. Uranium abundance in rock-forming minerals. In Wedepohl, K. H. (ed.) Handbook of Geochemistry, 92-D-1. Berlin: Springer-Verlag.Google Scholar
Steiger, R. H. & Jäger, E. 1977. Subcommission on geochronology: convention on the use of decay constants in geo- and cosmo- chronology. EARTH PLANET SCI LETT 36, 359–62.CrossRefGoogle Scholar
Taylor, H. P. & Forester, R. W. 1971. Low-O18 igneous rocks from the intrusive complexes of Skye, Mull and Ardnamurchan, Western Scotland. J PETROL 12, 465–97.CrossRefGoogle Scholar
Tuson, J. 1959. A geophysical investigation of the Tertiary volcanic districts of Western Scotland. Unpublished Ph.D. Thesis, Durham University.Google Scholar
Tyrrell, G. W. 1928. The geology of Arran. MEM GEOL SURV GB.Google Scholar
van Breemen, O. & Hawkesworth, C. J. 1980. Sm-Nd isotopic study of garnets and their metamorphic host rocks. TRANS R SOC EDINBURGH: EARTH SCI 71, 97–102.CrossRefGoogle Scholar
Wadge, A. J., Gale, N. H., Beckinsale, R. D. & Rundle, C. C. 1978. A Rb-Sr isochron for the Shap Granite. PROC YORKSHIRE GEOL SOC 42, 297–305.CrossRefGoogle Scholar
York, D. 1969. Least squares fitting of a straight line with correlated errors. EARTH PLANET SCI LETT 5, 320–4.CrossRefGoogle Scholar