Hostname: page-component-8448b6f56d-cfpbc Total loading time: 0 Render date: 2024-04-19T14:43:39.104Z Has data issue: false hasContentIssue false
  • English
  • Français

A stable isotopic (δ18O, δD) study of the late-Hercynian granites and their host-rocks in the Central Iberian Massif (Spain)

Published online by Cambridge University Press:  03 November 2011

C. Recio ,
A. E. Fallick  and
J. M. Ugidos
C. Recio
Affiliation:
C. Recio, Servicio General de Analisis de Isótopos Estables, Facultad de Ciencias,Universidad de Salamanca, 37008-Salamanca, Spain
A. E. Fallick
Affiliation:
A. E. Fallick, Isotope Geology Unit, Scottish Universities Research & Reactor Centre, East Kilbride, Glasgow G75 0QU, Scotland, U.K.
J. M. Ugidos
Affiliation:
J. M. Ugidos, Departamento de Geología, Facultad de Ciencias,Universidad de Salamanca, 37008-Salamanca, Spain
Get access Rights & Permissions [Opens in a new window]

Abstract

Stable isotopic ratios (mainly 18O/16O, but also D/H) have been measured for the three most important types of late-Hercynian granites, and their hosts, in the western area of the Central Iberian Massif (CIM), Spain. These granites are amphibole-bearing biotite granites, biotite granites and cordierite-bearing biotite granites. No intrusive relationships have been observed among them; the contact of each granite with the others is always gradational. Host-rocks are Precambrian/Cambrian metasediments, ranging from low-grade schists to migmatites (nebulites).

Whole-rock δ18OSMOW values are as follows: amphibole-bearing biotite granites 8·9 ± 0·58% (1σ, n = 17); biotite granites 9·0 ± 0·35% (1σ, n = 11); cordierite-bearing biotite granites 9·6 ± 0·24% (1σ, n = 21). δ18O values for nebulites, into which some of these granites were emplaced, are significantly higher, at 11·1 ± 0·58‰ (1σ, n = 13). The Precambrian to Cambrian shales gave an average value of δ18O = 11·9 ± l·23‰ (lδ, n = 5). Whole-rock oxygen isotope ratios indicate that the origin of the granites was in neither purely sedimentary/metasedimentary rocks nor pristine mantle melts. δ18O values close to 9·0‰ require a crustal protolith, having an important recycled component.

Oxygen isotope results are compatible with the cordierite-bearing granites being generated by assimilation of nebulite-like material by a biotite granite magma. However, 18O/16O of mineral separates obtained from the three different granites and the nebulite indicate that isotopic equilibrium, if ever reached, has not been preserved. The modified isotopic equilibrium is attributed to fluid activity, but mineral-pair δ-δ plots suggest that the granite system behaved as a closed system, and that the fluid was deuteric (magmatic) in origin. This implies that if assimilation did happen, it occurred at a temperature higher than the closure temperature of the different minerals to isotopic exchange. In a δ18O vs δD plot, hornblende and biotite separates from the granites plot within the igneous field. A simple mesocrustal anatectic origin for the peraluminous late Hercynian granites of the western area of the CIM is difficult to sustain on the basis of the stable isotope data, consistent with other field, petrographic and geochemical evidence. Cordierite in the cordierite-bearing granites is not “restitic” from a deep source area, but rather is xenocrystic from the high-grade metamorphic country rock (nebulites).

Keywords

Amphibole-bearing granitesassimilationbiotite granitescordierite-bearing granites
Type
Research Article
Information
Earth and Environmental Science Transactions of The Royal Society of Edinburgh , Volume 83 , Issue 1-2: Second Hutton Symposium: The Origin of Granites and Related Rocks , 1992 , pp. 247 - 257
Copyright
Copyright © Royal Society of Edinburgh 1992

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

Ben-Othman, D., Fourcade, S. & Allègre, C. J. 1984. Recycling processes in granite-granodiorite complex genesis: the Querigut case studied by Nd-Sr isotope systematics EARTH PLANET SCI LETT 69, 290–300.CrossRefGoogle Scholar
Borthwick, J. & Harmon, R. S. 1982. A note regarding CIF3 as an alternative to BrF5 for oxygen isotope analysis. GEOCHIM COSMOCHIM ACTA 46, 1665–8.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
Clayton, R. N. & Mayeda, T. K. 1963. The use of bromine pentafluroide in the extraction of oxygen from oxides and silicates for isotopic analysis. GEOCHIM COSMOCHIM ACTA 27, 43–52.CrossRefGoogle Scholar
Craig, H. 1961. Isotopic variations in meteoric waters. SCIENCE 133, 1702–3.CrossRefGoogle ScholarPubMed
Department of Petrology, University of Salamanca 1983. Mapa 1:200000 de la síntesis geológica del basamento. Zona del cento-oeste español. Salamanca: University of Salamanca.Google Scholar
Dobson, P. F., Epstein, S. & Stolper, E. M. 1989. Hydrogen isotope fractionation between coexisting vapor and silicate glasses and melts at low pressure. GEOCHIM COSMOCHIM ACTA 53, 2723–30.CrossRefGoogle Scholar
Fourcade, S., Peucat, J. J., Martineau, F., Cuesta, A., Corretgé, L. G. & Ibarguchi, I.Gil 1989. Análisis de isótopos de oxígeno y edad Rb-Sr del plutón zonado de Caldas de Reyes (Galicia, España). GEOGACETA 6, 7–9.Google Scholar
Fourcade, S. & Javoy, M. 1973. Rapports 18O/16O dans les roches du vieux socle catazonal d'ln Ouzzal (Sahara Algerien). CONTRIB MINERAL PETROL 42, 235–44.CrossRefGoogle Scholar
Friedman, I. & Gleason, J. D. 1973. Notes on the bromine pentafluoride technique of oxygen extraction. J RES US GEOL SURV 1(6) 679–80.Google Scholar
Garlick, G. D. 1966. Oxygen isotope fractionation in igneous rocks. EARTH PLANET SCI LETT 1, 361–8.CrossRefGoogle Scholar
Godfrey, J. D. 1962. The deuterium content of hydrous minerals from the East-Central Sierra Nevada and Yosemite National Park. GEOCHIM COSMOCHIM ACTA 26, 1215–45.CrossRefGoogle Scholar
Graham, C. M., Harmon, R. S. & Sheppard, S. M. F. 1984. Experimental hydrogen isotope studies. Systematics of hydrogen isotope exchange between amphibole and water. AM MINERAL 69, 128–38.Google Scholar
Gregory, R. T. & Criss, R. E. 1986. Isotopic exchange in open and closed systems”. In Valley, J. W., Taylor, H. P. Jr & O'Neil, J. R. (eds) Stable isotopes in high temperature geological processes. MSA REV MINERAL 161, 91–127.Google Scholar
Halliday, A. N., Stephens, W. E. & Harmon, R. S. 1980. Rb-Sr and O isotopic relationships in 3 zoned Caledonian granitic plutons, Southern Uplands, Scotland: Evidence for varied sources and hybridization of magma. J GEOL SOC LONDON 137, 329–49.CrossRefGoogle Scholar
Harmon, R. S. 1984. Stable isotope geochemistry of Caledonian granitoids from the British Isles and East Greenland. PHYS EARTH PLANET INT 35 (1-3), 105–20.CrossRefGoogle Scholar
Harmon, R. S. & Halliday, A. N. 1980. Oxygen and strontium isotope relationships in the British late Caledonian granites. NATURE 283, 21–5.CrossRefGoogle Scholar
Harmon, R. S., Halliday, A. N., Clayburn, J. A. P. & 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. PHILOS TRANS R SOC LONDON A310, 709–42.Google Scholar
Jenkin, G. R. T. 1988. Stable isotope studies in the caledonides of W. Connemara, Ireland. Unpublished Ph.D. Thesis, University of Glasgow, Glasgow.Google Scholar
Julivert, M., Fontboté, J. M., Ribeiro, A. & Conde, L. E. 1974. Memoria explicativa del Mapa Tectónico de la Peninsula Iberica y Baleares. A escala 1 :1,000.000. IGME. Madrid.Google Scholar
Kelley, S. & Bluck, B. J. 1989. Detrital mineral ages from the Southern Uplands using 40Ar-39 Ar laser probe. J GEOL SOC LONDON 146, 401–3.CrossRefGoogle Scholar
Lotze, F. 1945. Zur Gliederung der Varisziden der Iberischen Meseta. Spanish translation by J. M. Rios: Observaciones respecto a la división de las Variscides de la Meseta Ibérica. PUB EXTRANJERAS SOBRE GEOL ESPAÑA 5, 149–66 (1950).Google Scholar
Michard-Vitrac, A., Albarede, F., Dupuis, C. & Taylor, H. P. Jr.1980. The genesis of Variscan (Hercynian) plutonic rocks: inferences from Sr, Pb and O studies on the Maladeta igneous complex, central Pyrenees (Spain). CONTRIB MINERAL PETROL 72, 57–72.CrossRefGoogle Scholar
O'Neil, J. R., Shaw, S. E. & Flood, R. H. 1977. Oxygen and hydrogen isotope compositions as indicators of granite genesis in the New England Batholith, Australia. CONTRIB MINERAL PETROL 62, 313–28.CrossRefGoogle Scholar
O'Neil, J. R. & Chappell, B. W. 1977. Oxygen and hydrogen isotope relations in the Berridale Batholith. J GEOL SOC LONDON 133, 559–72.CrossRefGoogle Scholar
O'Neil, J. R. & Taylor, H. P. Jr 1967. The oxygen isotope and cation exchange chemistry of feldspars. AM MINERAL 52, 1414–37.Google Scholar
Recio, C. 1990. The late Hercynian granitoids of the western area the SCE: A stable (O, H, S) isotopic study. Unpublished Tesis Doctoral, Universidad de Salamanca, Salamanca.Google Scholar
Schreyer, W. 1985. Experimental studies on cation substitutions and fluid incorporation in cordierite. BULL MINERAL 108, 273–91.Google Scholar
Sheppard, S. M. F. 1977. The Cornubian Batholith, SW England: D/H and 18O/16O studies of kaolinite and other alteration minerals. J GEOL SOC LONDON 133, 573–91.CrossRefGoogle Scholar
Sheppard, S. M. F. 1986. Characterization and isotopic variations in natural waters. In Valley, J. W., Taylor, H. P. Jr & O'Neil, J. R. (eds) Stable isotopes in high temperature geological processes MSA REV MINERAL 16, 165–83.Google Scholar
Suzuoki, T. & Epstein, S. 1976. Hydrogen isotope fractionation between OH-bearing minerals and water. GEOCHIM COSMOCHIM ACTA 40, 1229–40.CrossRefGoogle Scholar
Taylor, B. E. 1986. Magmatic volatiles: Isotopic variation of C, H, and S. In Valley, J. W., Taylor, H. P. Jr & O'Neil, J. R. (eds) Stable isotopes in high temperature geological processes MSA REV MINERAL 16, 185–225.Google Scholar
Taylor, H. P. Jr 1968. The oxygen isotope geochemistry of igneous rocks. CONTRIB MINERAL PETROL 19, 1–71.CrossRefGoogle Scholar
Taylor, H. P. Jr 1977. Water/rock interactions and the origin of H2O in granitic batholiths (Thirtieth William Smith Lecture). J GEOL SOC LONDON 133, 509–58.CrossRefGoogle Scholar
Taylor, H. P. Jr 1980. The effects of assimilation of country rocks by magmas on 18O/16O and 86Sr/86Sr systematics in igneous rocks. EARTH PLANET SCI LETT 47, 243–54.CrossRefGoogle Scholar
Taylor, H. P. Jr 1986. Igneous rocks: II. Isotopic case studies of circumpacific magmatism. In Valley, J. W., Taylor, H. P. Jr& O'Neil, J. R. (eds) Stable Isotopes in high temperature geological processes MSA REV MINERAL 16, 273–317.Google Scholar
Taylor, H. P. Jr 1988. Oxygen, hydrogen and strontium isotope constraints on the origin of granites. TRANS R SOC EDINBURGH EARTH SCI 79, 317–38.Google Scholar
Taylor, H. P. Jr & Sheppard, S. M. F. 1986. Igneous rocks: I. Processes of isotopic fractionation and isotope systematics. In Valley, J. W., Taylor, H. P. Jr. & O'Neil, J. R. (eds) Stable isotopes in high temperature geological processes. MSA REV MINERAL 16, 227–71.Google Scholar
Ugidos, J. M. 1988. New aspects and considerations on the assimilation of cordierite-bearing rocks. REV SOC GEOL ESPAÑA 1, 129–33.Google Scholar
Ugidos, J. M. 1990. Granites in the Central Iberian Massif as a Paradigm of Genetic Processes of Granitic Rocks: I-Types vs S-Types. In Dallmeyer, R. D. & García, E.Martínez (eds) Pre-Mesozoic Geology of Iberia, 189–206. Berlin: Springer.Google Scholar
Ugidos, J. M. & Recio, C. 1991. Geochemical characterization of late Hercynian granites from the Western Central Iberian Massif (CIM; Spain): Constraints on the origin of cordieritebearing biotite granites. CHEM GEOL (submitted).Google Scholar
Valley, J. W., Taylor, H. P. Jr & O'Neil, J. R. (eds) 1986. Stable isotopes in high temperature geological processes, MSA REV MINERAL 16. Chelsea, Michigan: BookCrafters.Google Scholar
Wilson, A. F., Green, D. C. & Davidson, L. R. 1970. The use of oxygen isotope geothermometry on granulties and related intrusives, Musgrave Ranges, Central Australia. CONTRIB MINERAL PETROL 27, 166–78.CrossRefGoogle Scholar