Hostname: page-component-cd9895bd7-p9bg8 Total loading time: 0 Render date: 2024-12-26T21:56:37.629Z Has data issue: false hasContentIssue false
  • English
  • Français

The conditions of metamorphism of a grossular—wollastonite vesuvianite skarn from the Omey Granite, Connemara, western Ireland, with special reference to the chemistry of vesuvianite

Published online by Cambridge University Press:  05 July 2018

Y. Ahmed-Said  and
Bernard E. Leake
Y. Ahmed-Said
Affiliation:
Department of Geology and Applied Geology, University of Glasgow, Glasgow G12 8QQ, UK
Bernard 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 Fountain Hill skarn, which was produced by thermal metamorphism of impure limestone in the Omey Granite aureole, consists of wollastonite, calcite, grossular-andradite garnet, diopside, B-free vesuvianite and small amounts of albite, K-feldspar and quartz. Zoning in vesuvianite is, overall, independent of birefringence but oscillatory concentric zoning in the mineral is controlled mainly by Ti. In addition to extensive within-site substitutions (e.g. F for OH in the OH-sites, Fe2+ for Mg, Fe3+ for Al, Ti for Al etc. in the Y-sites), there are significant cross-site combined substitutions involving Y-X and Y-Z but not X-Z sites so that ideal solution models for this mineral are not applicable. The thermodynamic mole fraction of Hoisch (1985) is modified to account for the excess of the ΣY cations in the Y sites and can be applied to both B-bearing and B-free vesuvianites. Using the thermodynamic dataset of Holland and Powell (1990) and taking into account the existence of andalusite, sillimanite and corundum in associated pelites, leads to the conclusion that the metamorphic conditions were about 640±20°C and 3.3±0.3 kb at 0.15±0.05 XCO2.

Keywords

activitygrossularhornfelsthermodynamic mole fractionvesuvianitewollastonite
Type
Petrology
Information
Mineralogical Magazine , Volume 60 , Issue 401 , August 1996 , pp. 541 - 550
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1996

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

*

Previous address: Oum-Toub (Skikda), P.O. Box 56, 21450, Algeria

References

Bucher-Nurminen, K. (1990) Geological phase diagram software. Terra, 4, 401–10.Google Scholar
Deer, W.A., Howie, R.A. and Zussman, J. (1982) Rockforming minerals volume 1A, Longman, London.Google Scholar
Ebadi, A. and Johannes, W. (1991) Beginning of melting and composition of first melts in the system Qz-Ab- Or-H2O-CO2- Contrib. Mineral. Petrol., 106, 286–95.CrossRefGoogle Scholar
Ferguson, C.C. and Al-Ameen, S.I. (1985) Muscovite breakdown and corundum growth at anomalously low fH2O: A study of contact metamorphism and convective fluid movement around the Omey Granite, Connemara, Ireland. Mineral. Mag., 49, 505–14.CrossRefGoogle Scholar
Ferguson, C.C. and Harvey, P.K. (1979) Thermally overprinted Dalradian rocks near Cleggan, Connemara, western Ireland. Proc. Geologists' Assoc. y 90, 43—50.Google Scholar
Ferry, J.M. (1994) Role of fluid flow in the contact metamorphism of siliceous dolomitic limestones. Amer. Mineral. 79, 719—36.Google Scholar
Frimmel, H.E. and van Achterbergh, E. (1995) Metamorphism of calc-silicate and associated rocks in the Pan-African Kaaimans Group, Saldania Belt, South Africa. Mineral. Petrol., 53, 75–102.CrossRefGoogle Scholar
Gibson, R.L. and Wallmach, T. (1995) Complex zoning in vesuvianites from the Canigou Massif, Pyrenees, France. Canad. Mineral, 33, 77–84.Google Scholar
Groat, L.A., Hawthorne, F.C. and Ercit, T.S. (1992a) The chemistry of vesuvianite. Canad. Mineral., 30, 19–48.Google Scholar
Groat, L.A., Hawthorne, F.C. and Ercit, T.S. (1992b) The role of fluorine in vesuvianite: a crystal- structure study. Canad. Mineral., 30, 1065–75.Google Scholar
Groat, L.A., Hawthorne, F.C. and Ercit, T.S. (1994a) Excess Y-group cations in the crystal structure of vesuvianite. Canad. Mineral, 32, 497–504.Google Scholar
Groat, L.A., Hawthorne, F.C. and Ercit, T.S. (1994b) The incorporation of boron into vesuvianite structure. Canad. Mineral., 32, 505–23.Google Scholar
Groat, L.A., Hawthorne, F.C., Rossman, G.R. and Ercit, T.S. (1995) The infrared spectroscopy of vesuvianite in the OH region. Canad. Mineral., 33, 609–26.Google Scholar
Hoisch, T.D. (1985) The solid solution chemistry of vesuvianite. Contrib. Mineral. Petrol, 89, 205–14.CrossRefGoogle Scholar
Holdaway, M.J. and Mukhopadhyay (1993) A reevaluation of the stability relations of andalusite: Thermochemical data and phase diagram for aluminium silicates. Amer. Mineral, 78, 298–315.Google Scholar
Holland, T.J.B. and Powell, R. (1985) An internally consistent thermodynamic dataset with uncertainties and correlations. II Data and results. J. Meta. Geol., 3, 343–70.CrossRefGoogle Scholar
Holland, T.J.B. and Powell, R. (1990) An internally consistent thermodynamic dataset with uncertainties and correlations: The system Na2O-K2O-CaO-MgO- MnO-FeO-Fe2O3-Al2O3-SiO2-TiO2-C-H2O2 J.Meta. GeoL, 8, 89–124.CrossRefGoogle Scholar
Kerrick, D.M., Crawford, K.E. and Randazzo, A.F. (1973) Metamorphism of calcarous rocks in three roof pendants in the Sierra Nevada, California. J. Petrol., 14, 303-25.CrossRefGoogle Scholar
Leake, B.E. and Tanner, P.W.G. (1994) The geology of the Dalradian and associated rocks of Connemara, Western Ireland. Royal Irish Academy, Dublin 96pp.Google Scholar
Leake, B.E., Tanner, P.W.G., and Senior A. (1975) The composition and origin of the Connemara dolomitic marbles and ophicalcites. J. Petrol, 16, 237–57.CrossRefGoogle Scholar
Leggo, P., Compston, W. and Leake, B.E. (1966) The geology of the Connemara granites and its bearing on the antiquity of the Dalradian series. Q. J. Geol. Soa, 122, 91–116.CrossRefGoogle Scholar
Powell, R. and Holland, TJ.B. (1985) An internally consistent thermodynamic dataset with uncertainties and correlations. I Methods and worked example. J. Meta. Geoi, 3, 327–42.CrossRefGoogle Scholar
Powell, R. and Holland, TJ.B. (1988) An internally consistent thermodynamic dataset with uncertainties and correlations. Ill Application methods, worked examples and a computer program. J. Meta. Geol, 6, 173–204.CrossRefGoogle Scholar
Powell, R. and Holland, TJ.B. (1994) Optimal geothermometry and geobarometry. Amer. Mineral. 79, 120—33.Google Scholar
Richardson, S.W., Gilbert, M.C. and Bell, P.M. (1969) Experimental determination of kyanite-andalusite and andalusite-sillimanite equilibrium; the aluminium silicate triple point. Amer. J. Sci., 267, 259–72.CrossRefGoogle Scholar
Salje, E. (1986) Heat capacities and entropies of andalusite and sillimanite: the influence of fibroliti- sation on the phase diagram of the Al2Si05 polymorphs. Amer. Mineral, 71, 1366–71.Google Scholar
Townend, R. (1966) The geology of some granite plutons from western Connemara, Co, Galway. Proc. Roy. Ir. Acad., 65(B), 157—202.Google Scholar
Valley, J.W., Peacor, D.R., Bowman, J.R., Essene, E.J. and Allard, M.J. (1985) Crystal chemistry of Mg- vesuvianite and implications of phase equilibria in the system CaO-MgO-Al2O3-SiO2-H2O-CO2. J. Meta. GeoL, 13, 1 — 12.Google Scholar