Hostname: page-component-76dd75c94c-lntk7 Total loading time: 0 Render date: 2024-04-30T07:33:35.869Z Has data issue: false hasContentIssue false
  • English
  • Français

S-type granite formation in the Dalradian rocks of Connemara, W. Ireland

Published online by Cambridge University Press:  05 July 2018

Y. Ahmed-Said  and
B. E. Leake
Y. Ahmed-Said
Affiliation:
Department of Geology and Applied Geology, University of Glasgow, Glasgow G12 8QQ, UK
B. E. Leake
Affiliation:
Department of Geology and Applied Geology, University of Glasgow, Glasgow G12 8QQ, UK
Get access Rights & Permissions [Opens in a new window]

Abstract

The vicinity of the 490 Ma Cashel gabbroic intrusion experienced pressures of about 4.05 ± 0.2 kbar and temperatures in excess of 850 °C. These conditions caused intense hornfelsing and partial melting of the surrounding Dalradian metasediments. From the study of the progressively changed composition of the aureole hornfelses it is deduced that elements were fractionated into the melts as follows: Si>K>Na>Ca>Mn>Al>Fe>Mg and Rb>Ba>Sr>Ga>Cr,Ni,Co. This order of fractionation, which is the opposite to that in magmatic crystallization, provides a detailed picture of the mode of interaction between a mantle derived basic magma and mid-crustal rocks, illustrating how one type of S-type granite can be produced. The rare earth elements (REE) were both removed and fractionated but Eu largely remained in the crystal fractions giving increasing positive Eu anomalies with rising partial melting and these trends can be explained by the extraction of a granitic melt from the hornfelses. Fission track mapping of U is used to study the behaviour of U within the aureole and the metamorphic recrystallization of detrital brown zircon to pink new zircon. The S-type Cashel microgranite sill is shown to have been derived by anatexis from the Dalradian rocks, to have preserved the Sr isotope ratios of the metasediments at 490 Ma, and not to be of the same composition as the leucosomes in the metasediments.

Keywords

S-type granitecrustal melthornfelsesDalradianIreland
Type
Geochemistry and Petrology
Information
Mineralogical Magazine , Volume 54 , Issue 374 , March 1990 , pp. 1 - 22
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1990

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.)

Footnotes

*

Now Department of Geology, Earth Sciences Institute, University of Annaba, Algeria

References

Abbot, R. N. and Clarke, D. B. (1979) Hypothetical liquidus relationships in the subsystem Al2O3-FeO-MgO projected from quartz, alkali feldspar and plagioclase for a(H2O)⩽ 1. Can. Mineral. 17, 549-60.Google Scholar
Ahmed-Said, Y. (1988) The geochemistry of thermal aureoles at Cashel, Co Galway, and Comrie, Perthshire. Ph.D thesis, Univ. of Glasgow (unpub.).Google Scholar
Barber, J. P. (1985) High-grade metamorphism and melting in the Dalradian of eastern Connemara, Ireland. Ph.D thesis, Univ. of East Anglia (unpub.)CrossRefGoogle Scholar
Barber, J. P. and Yardley, B. W. D. (1985) Conditions of high grade metamorphism in the Dalradian of Connemara, Ireland. J. Geol. Soc. Lond. 142, 87-96.CrossRefGoogle Scholar
Barr, D. (1985) Migmatites in the Moines. In Migmatites (Ashworth, J. R., ed.). Blackie, Glasgow, 225-64.CrossRefGoogle Scholar
Bowen, N. L. (1928) The evolution of igneous rocks. Princeton University Press, 332 pp.Google Scholar
Carslaw, H. S. and Jaeger, J. C. (1947) Conduction of heat in solids. Oxford Univ. Press, 386 pp.Google Scholar
Carslaw, H. S. and Jaeger, J. C. (1959) Ibid., 2nd ed., 510 pp.Google Scholar
Chappell, B. W. and White, A. J. R. (1974) Two contrasting granite types. Pacific geol. 8, 173-4.Google Scholar
Clemens, J. D. and Wall, V. J. (1981) Origin and crystallization of some peraluminous (S-type) granitic magmas. Can. Mineral. 19, 111-31.Google Scholar
Dallmeyer, R. D. (1974) The role of crystal structure in controlling the partitioning of Mg and Fe+2 between coexisting garnet and biotite. Am. Mineral. 59, 201-3.Google Scholar
Drury, S. A. (1978) REE distributions in high-grade Archean gneiss complex in Scotland: Implications for the genesis of ancient sialic crust. Preeambrian Res. 7, 237-57.CrossRefGoogle Scholar
Evans, B. W. (1964) Fractionation of elements in the pelitic hornfelses of the Cashel-Lough Wheelaun intrusion, Connemara, Eire. Geochim. Cosmochim. Acta, 28, 127-56.CrossRefGoogle Scholar
Evans, B. W. and Leake, B. E. (1970) The geology of the Toombeola district, Connemara, Co. Galway. Proe. Roy. Irish Acad. 70B, 105-39.Google Scholar
Ferry, J. M. and Spear, F. S. (1978) Experimental calibration of the partitioning of Fe and Mg between biotite and garnet. Contrib. Mineral. Petrol. 66, 113-17.CrossRefGoogle Scholar
Flynn, R. T. and Burnham, C. W. (1978) An experimental determination of rare earth partition coefficients between a chloride containing vapor phase and silicate melts. Geochim. Cosmochim. Acta, 42, 685-701.CrossRefGoogle Scholar
Fraser, D. H. (1975) Activities of trace elements in silicate melts. Ibid. 39, 1525-30.CrossRefGoogle Scholar
Ghent, E. D. (1976) Plagioclase-garnet-Al2SiO5-quartz: a potential geobarometer-geothermometer. Am. Mineral. 61, 710-14.Google Scholar
Ghent, E. D., Robbins, D. B. and Stout, M. Z. (1979) Geothermometry, geobarometry and fluid compositions of metamorphosed calc-silicates and pelites, Mica Creek, British Columbia. Ibid. 64, 874-85.Google Scholar
Grant, J. A. and Weiblen, P. W. (1971) Retrograde zoning in in garnet near the second sillimanite isograde. Am. J. Sci. 270, 281-96.CrossRefGoogle Scholar
Grauert, B., Seitz, M. G. and Soptrajanova, G. (1974) Uranium and lead gain of detrital zircon studied by isotopic analyses and fission track mapping. Earth Planet. Sci. Lett. 21, 38-99.CrossRefGoogle Scholar
Green, T. H. (1976) Experimental generation of cordierite- or garnet-bearing granitic liquids from a pelitic composition. Geol. 4, 85-8.2.0.CO;2>CrossRefGoogle Scholar
Harmon, R. S., Halliday, A. N., Clayburn, J. A. P. and Stephens, W. E. (1984) Chemical and isotopic systematics of the Caledonian intrusions of Scotland and northern England: a guide to magma source region and magma-crust interaction. Phil. Trans. Roy. Soc. Lond. A310, 709-42.Google Scholar
Heier, K. S. and Adams, J. A. S. (1965) Concentration of radioactive elements in deep crustal material. Geochim. Cosmochim. Acta, 29, 53-61.CrossRefGoogle Scholar
Henderson, P. (1984) General geochemical properties and abundances of the rare earth elements. In Rare Earth Element Geochemistry (Henderson, P., ed.. Developments in Geochemistry, 2. Elsevier, Amsterdam, 1–13.CrossRefGoogle Scholar
Hodges, K. V. and Spear, F. S. (1982) Geothermometry, geobarometry and the Al2SiO5 triple point at Mt. Moosilauke, New Hampshire. Am. Mineral. 67, 1118-34.Google Scholar
Holdaway, M. J. and Lee, S. M. (1977) Cordierite stability in high-grade pelitic rocks based on experimental, theoretical and natural observations. Contrib. Mineral. Petrol. 63, 175-98.CrossRefGoogle Scholar
Huppert, H. E. and Sparks, R. S. J. (1988) The generation of granitic magmas by intrusion of basalt into continental crust. J. Petrol. 29, 59-624.CrossRefGoogle Scholar
Indares, A. and Martignole, J. (1985) Biotite-garnet geothermometry in granulite facies: the influence of Ti and A1 in biotite. Am. Mineral. 70, 272-8.Google Scholar
Jaeger, J. C. (1958) The temperature in the neighbourhood of a cooling intrusive sheet. Am. J. Sci. 255, 306-18.CrossRefGoogle Scholar
Jaeger, J. C. (1959) Temperature outside a cooling intrusive sheet. Ibid. 257, 44-54.CrossRefGoogle Scholar
Jagger, M. D. (1985) The Cashel district of Connemara, Co Galway, Eire: an isotopic study. Ph.D. thesis, Univ. Glasgow (unpub.).Google Scholar
Jagger, M. D., Max, M. D., Aftalion, M., and Leake, B. E. (1988) U-Pb zircon ages of basic rocks of Cashel, Connemara, Western Ireland. J. Geol. Soc. Lond. 145, 645-8.CrossRefGoogle Scholar
Jenkin, J. R. T. (1988) Stable isotope studies in the Caledonides of SW Connemara, Ireland. Ph.D. thesis, Univ. Glasgow (unpub).Google Scholar
Johannes, W. (1985) The significance of experimental studies for the formation of migmatites. In Migmatites (Ashworth, J. R., ed.) Blackie, Glasgow, 36–85.CrossRefGoogle Scholar
Laouar, R. (1988) A sulphur isotope study of the Caledonian granites of Britain and Ireland. M.Sc. thesis, Univ. Glasgow (unpub.).Google Scholar
Leake, B. E. (1958a) The Cashel Lough Wheelaun intrusion, Co Galway, Ireland. Proc. Roy. Irish Acad. 59B , 155–203.Google Scholar
Leake, B. E. (1958b) Composition of pelites from Connemara, Co, Galway, Ireland. Geol. Mag. 95, 281-96.CrossRefGoogle Scholar
Leake, B. E. (1970) The fragmentation of the Connemara basic and ultrabasic intrusions. In Mechanisms of igneous intrusion (Newall, G. and Rast, N., eds.) Geol. J. Speciallssue, no. 2, 103-22.Google Scholar
Leake, B. E. (1989) The metagabbros, orthogneisses and paragneisses of the Connemara complex, Western Ireland. J. Geol. Soc. Lond. 146, 575-96.CrossRefGoogle Scholar
Leake, B. E. and Skirrow, G. (1960) The pelitic hornfelses of the Cashel-Lough Wheelaun intrusion, Co. Galway, Eire. J. Geol. 68, 23-40.CrossRefGoogle Scholar
Le Breton, N. and Thompson, A. B. (1988) Fluidabsent (dehydration) melting of biotite in metapelites in the early stages of crustal anatexis. Contrib. Mineral. Petrol. 99, 226-37.CrossRefGoogle Scholar
Luth, W. C., Jahns, R. H., and Tuttle, O. F. (1964) The granite system at pressures of 4 to 10 Kbs. J. Geophy. Res. 69, 75-73.Google Scholar
Manning, D. A. C. (1981) The effect of fluorine on liquidus phase relationships in the system Qz:Ab:Or with excess water at 1 Kb. Contrib. Mineral. Petrol. 76, 206-15.CrossRefGoogle Scholar
Manning, D. A. C. and Pichavant, M. (1983). The role of fluorine and boron in the generation of granitic melts. In Migmatities, melting and metamorphism (Atherton, M. P. and Gribble, C. D., eds.) Shiva, Orpington, 94–109.Google Scholar
McCarty, T. S. and Kable, E. J. C. (1978) On the behaviour of the rare-earth elements during partial melting of granitic rocks. Chem. Geol. 22, 21-9.CrossRefGoogle Scholar
Newton, R. C. and Haselton, H. T. (1981) Thermodynamics of the garnet-plagioclase-Al2SiO5-quartz geobarometer. In Thermodynamics of minerals and melts (Newton, R. C., Navrotsky, A., and Wood, B. J., eds.) Springer-Verlag, New York, 131-47.CrossRefGoogle Scholar
Pichavant, M. (1981) An experimental study of the effect of boron on a water saturated haplogranite at 1 Kb vapour pressure. Geological applications. Contrib. Mineral Petrol 76, 430-9.CrossRefGoogle Scholar
Read, H. H. and Watson, J. (1982) Introduction to geology, 1. Macmillan.Google Scholar
Rogers, N. W. (1977) Granulite xenoliths from Lesotho Kimberlites and the lower continental crust. Nature, Lond. 270, 681-4.CrossRefGoogle Scholar
Sawyer, E. W. and Barnes, S.-J. (1988) Temporal and compositional differences between subsolidus and anatectic migmatite leucosomes from the Quetico metasedimentary belt, Canada. J. Metam. Petrol. 6, 437-50.CrossRefGoogle Scholar
Senior, A. and Leake, B. E. (1978) Regional metamorphism and the geochemistry of the Dalradian metasediments of Connemara, western Ireland. J. Petrol. 19, 585-625.CrossRefGoogle Scholar
Sun, C. O., Williams, R. J. and Sun, S. S. (1974) Distribution coefficients of Eu and Sr for plagioclase-liquid and clinopyroxene-liquid equilibria in oceanic ridge basalt: an experimental study. Geochim. Cosmochim. Acta, 38, 1415-33.Google Scholar
Taylor, S. R. and McLennan, S. M. (1955) The continental crust: its composition and evolution. Blackwell Scientific Publications, Oxford, 312 pp.Google Scholar
Thompson, A. B. (1976) Mineral reactions in pelitic rocks: II. Calculation of some P-T-X (Fe-Mg) phase relations. Am. J. Sci. 276, 425-54.CrossRefGoogle Scholar
Thompson, A. B. (1982) Dehydration melting of pelitic rocks and the generation of H20-undersaturated granitic liquids. Ibid. 282, 1567-95.Google Scholar
Thompson, A. B. and Tracy, R. J. (1979) Model systems for anatexis of pelitic rocks. II. Facies series melting and reactions in the system KAlO2-NaAlO2-Al2O3-SiO2-H2O. Contrib. Mineral. Petrol. 70, 429-38.CrossRefGoogle Scholar
TiUey, C. E. (1924) Contact metamophism in the Comrie area of the Perthshire Highlands. Q. J. Geol. Soc. Lond. 80, 22–71.Google Scholar
Tracy, R. J. (1978) High-grade metamorphic reactions and partial melting in pelitic schist, western-central Masschusetts. Am. J. Sci. 278, 150-78.CrossRefGoogle Scholar
Tracy, R. J. (1985) Migmatite occurrences in New England. In Migmatites (Ashworth, J. R., ed.) Blackie, Glasgow, 204-24.CrossRefGoogle Scholar
Treloar, P. J. (1981) Garnet-biotite-cordierite thermometry and barometry in the Cashel thermal aureole, Connemara, Ireland. Mineral. Mag. 44, 183-9.CrossRefGoogle Scholar
Tracy, R. J. (1985) Metamorphic conditions in central Connemara, Ireland. J. Geol. Soc. Lond. 142, 77-86.Google Scholar
Tuttle, O. F. and Bowen, N. L. (1958) Origin of granite in the light of experimental studies in the system NaAlSi3O8-KAlSi3O8-SiO2-H2O . Mem. Geol. Soc. Am. 74, 173 pp.Google Scholar
Vielzeuf, D. and Holloway, J. R. (1988) Experimental determination of the fluid absent melting relations in the pelitic system. Consequences for crustal differentiation. Contrib. Mineral. Petrol. 98, 257-76.CrossRefGoogle Scholar
Wells, P. R. A. and Richardson, S. W. (1980) Thermal evolution of metamorphic rocks in the central Highlands of Scotland. In The Caledonides of the British Isles—reviewed (Harris, A. L., Holland, C. H. and Leake, B. E., eds.) Spec. Publ. Geol. Soc. London, 8, 339-44.Google Scholar
Winkler, H. G. F. (1976) Petrogenesis of Metamorphic Rocks, 4th ed. Springer-Verlag, New York, 334 pp.CrossRefGoogle Scholar
Winkler, H. G. F. (1979) Ibid., 5th ed. Springer-Verlag. New York, 348 pp.Google Scholar
Yardley, B. W. D. (1978) Genesis of the Skagit Gneiss migmatities, Washington, and the distinction between possible mechanisms of migmatization. GeM Soc. Am. Bull. 89, 941-51.2.0.CO;2>CrossRefGoogle Scholar
Yardley, B. W. D. (1987) Discussion on the geochemistry of Dalradian pelites from Connemara, Ireland: New constraints on kyanite genesis and conditions of metamorphism. J. Geol. Soc. Lond. 144, 679-80.Google Scholar
Yardley, B. W. D. , Leake, B. E. and Farrow, C. M. (1980) The metamorphism of Fe-rich pellites from Connemara, Ireland. J. Petrol. 21, 365-99.CrossRefGoogle Scholar
Yardley, B. W. D., Barber, J. P. and Gray, J. R. (1987) The metamorphism of the Dalradian rocks of western Ireland and its relation to tectonic setting.. Phil. Trans. Roy. Soc. Lond. 321, 243-70.Google Scholar