Hostname: page-component-cd9895bd7-jkksz Total loading time: 0 Render date: 2024-12-29T03:42:17.788Z Has data issue: false hasContentIssue false
  • English
  • Français

Coupled Substitutions in Schorl-Dravite Tourmaline: New Evidence from SE Ireland

Published online by Cambridge University Press:  05 July 2018

V. Gallagher
V. Gallagher*
Affiliation:
Geology Department, University College, Dublin, Ireland
Get access Rights & Permissions [Opens in a new window]

Abstract

Analyses of tourmaline and coexisting muscovite in tourmaline-bearing rocks from SE Ireland indicate that the content of Si in tourmaline is not fixed but is dependent on bulk chemistry, varying inversely with Al. Zoning patterns within tourmaline reflect this and, despite theoretical objections, substitution of Si by Al in the tetrahedral site must occur in nature. Ti may also substitute for Si. Ca and Ti are generally involved in a coupled substitution. Estimates of the degree of alkali-defect and proton-loss substitution in SE Ireland tourmalines indicate that the former process is at least as important as the latter and that bulk chemistry is important in determining which substitution occurs. The general importance of alkali-defect substitution and Al⇌Si suggests that the most useful way to treat microprobe data for schorl-dravite tourmalines is to assume the presence of 3B and 4(OH) and calculate on the basis of 24.5 oxygen atoms.

Keywords

coupled substitutionsschorl-dravitetourmalineIreland
Type
Mineralogy
Information
Mineralogical Magazine , Volume 52 , Issue 368 , December 1988 , pp. 637 - 650
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1988

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

*

Present address: Department of Geology, University College, Cork, Ireland.

References

Ayuso, R.A. and Brown, C.E. (1984) Manganese-rich red tourmaline from the Fowler Talc Belt, New York. Can. Mineral. 22, 327-31.Google Scholar
Brindley, J. C. (1957) The aureole rocks of the Leinster Granite in south Dublin, Ireland. Proc. Roy. Ir, Acad. B59, 1-18.Google Scholar
Brindley, J. C. (1973) The structural setting of the Leinster Granite, Ireland—a review. Sci. Proc. Roy. Dub. Soc. 5A, 27–36.Google Scholar
Brück, P.M., Colthurst, J.R.J., Feely, M., Gardiner, P.R.R., Penney, S.R., Reeves, T.J., Shannon, P.M., Smith, D.G., and Vanguestaine, M. (1979) Southeast Ireland: Lower Palaeozoic stratigraphy and depositional history. In The Caledonides of the British Isles—-reviewed (Harris, A.L., Holland, C.H., and Leake, B.E., eds.). Geol. Soc. Lond. Spec. Pub. No. 8, 533-44.Google Scholar
Deer, W.A., Howie, R.A., and Zussman, J. (1962) Rock-forming minerals, 1 (Ortho and ring silicates), Longman.Google Scholar
Deer, W.A., Howie, R.A., and Zussman, J. (1978) Ibid. 2A (Single-chain silicates), 2nd ed., Longman.Google Scholar
Deer, W.A., Howie, R.A., and Zussman, J. (1986) Ibid. 1B (Disilicates and ring silicates), 2nd ed., Longrnan.Google Scholar
Dunham, A.C. and Wilkinson, F.C.F. (1978) Accuracy, precision and detection limits of energy-dispersive electron microprobe analyses of silicates. X-ray Spectrometry, 7, 50-6.Google Scholar
Ethier, V.G. and Campbell, F.A. (1977) Tourmaline concentrations in Proterozoic sediments of the Southem Cordillera of Canada and their economic significance. Can. J. Earth Sci. 14, 2348-63.Google Scholar
Foit, F.F. and Rosenberg, P.E. (1977) Coupled substitution in the tourmaline group. Contrib. Mineral. Petrol. 62, 109-27.CrossRefGoogle Scholar
Fortier, S. and Donnay, G. (1975) Schorl refinement showing composition dependence of the tourmaline structure. Can. Mineral. 13, 173-7.Google Scholar
Gallagher, V. (1987) Tourmaline-bearing rocks and granite-related metallogenesis in SE Ireland. Unpub. Ph.D. thesis, Nat. Univ. Ireland.Google Scholar
Gallagher, V. and Kennan, P.S. (in prep.) The geology and geochemistry of tourmaline associated with lithium pegmatites in SE Ireland.Google Scholar
Harder, H. (1959) Beitrag zur geochemie des bors—-I. Bor in mineralen und magmatischen gesteinen. Nachr. Akad. Wiss. Gottingen: H. Math-Physik KI., No. 5, 67-122.Google Scholar
Henry, D.J. and Guidotti, C.V. (1985) Tourmaline as a petrogenetic indicator mineral: an example from the staurolite-grade metapelites of NW Maine. Am. Mineral. 70, 1-15.Google Scholar
Jolliff, B.L., Papike, J.J., Shearer, C.K., and Laul, J.C. (1986) Tourmaline as a recorder of pegmatite evolution: Bob Ingersoll pegmatite, Black Hills, South Dakota. Ibid. 71, 472-500.Google Scholar
Kennan, P.S. (1983) Tourmalinites from Belgium and from southeast Ireland—-a discussion. Mineral. Mag. 47, 236-8.Google Scholar
Loewenstein, W. (1956) Boron in tetrahedra of borates and borosilicates. Am. Mineral. 41, 349-51.Google Scholar
McArdle, P. (1984) A study of the geological setting of mineralization associated with the Tullow Lowlands Unit of the Leinster Granite. Unpub. Ph.D. thesis, Nat. Univ. Ireland.Google Scholar
Manning, D.A.C. (1982) Chemical and morphological variation in tourmalines from the Hub Kapong batholith of peninsular Thailand. Mineral. Mag. 45, 139-47.Google Scholar
Nuber, B. and Schmetzer, K. (1979) The lattice position of Cr3+ in tourmaline: structural refinement of a chromium-rich Mg-A1 tourmaline (in German). Neues Jahrb. Mineral. Abh. 137, 184-97.Google Scholar
Peltola, E., Vuorelainen, Y., and Hakli, T.A. (1968) A chromium tourmaline from Outokumpu, Finland. Bull. Geol. Soc. Finland, 40, 358.Google Scholar
Reed, S.J.B. (1975) Electron microprobe analysis. Cambridge Monographs on Physics, Cambridge University Press.Google Scholar
Rosenberg, P.E. and Foit, F.F. (1979) Synthesis and characterization of alkali-free tourmaline. Am. Mineral. 64, 180-6.Google Scholar
Scoon, R.N. (1978) Lithium pegmatites in the Leinster Granite of southeast Ireland. Unpub. M.Sc. thesis, University College Cardiff, Wales.Google Scholar
Shearer, C.K., Papike, J.J., Simon, S.B., Laul, J.C., and Christian, R.P. (1984) Pegmatite/wallrock interactions, Black Hills, South Dakota: progressive boron metasomatism adjacent to the Tip Top Pegmatite. Geochim. Cosmochim. Acta, 48, 256-3. 79.Google Scholar
Slack, J.F., Herriman, N., Barnes, R.G., and Plimer, I.R. (1984) Stratiform tourmalinites in metamorphic terranes and their geologic significance. Geology, 12, 713-16.Google Scholar
Staatz, M.H., Murata, K.J., and Glass, J.J. (1955) Variation of composition and physical properties of tourmaline with its position in the pegmatite. Am. Mineral. 40, 789-804.Google Scholar
Steiger, R. and von Knorring, O. (1974) A lithium pegmatite belt in Ireland. J. Earth Sci. Leeds Geol. Assoc. 8, 433-43.Google Scholar
Sweatman, T.R. and Long, J.V.P. (1969) Quantitative electron-probe microanalysis of rock-forming minerals. J. Petrol. 10, 332-79.Google Scholar
Weisbrod, A. (1987) Crystal chemistry of Na-Mg- A1 tourmalines. EUG IV/EGS XII Joint meeting, Strasbourg, April 1987. (Abstract). Terra Cognita, 7, pp. 384.Google Scholar