Hostname: page-component-77c89778f8-gq7q9 Total loading time: 0 Render date: 2024-07-17T06:03:08.406Z Has data issue: false hasContentIssue false
  • English
  • Français

Skarn formation between metachalk and agglomerate in the Central Ring Complex, Isle of Arran, Scotland

Published online by Cambridge University Press:  05 July 2018

G. Cressey
G. Cressey*
Affiliation:
Department of Mineralogy, British Museum (Natural History), Cromwell Road, London, SW7 5BD
Get access Rights & Permissions [Opens in a new window]

Abstract

A skarn mineral assemblage occurs at the junction between vent pyroclastics and a xenolithic Cretaceous chalk block which subsided into the collapsed caldera of the Central Ring Complex, Isle of Arran, Scotland. Adjacent to the metachalk marble an andradite garnet exoskarn zone has developed at the expense of the carbonate. An andradite grossular/diopsidic clinopyroxene endoskarn zone has formed in the surrounding agglomerate, and a magnetite exoskarn is present in places between the andradite and garnet/pyroxene zones. The andraditic exoskarn garnets have fluor-hydrogarnet components, indicating that fluorine was present in the metasomatic fluid. From petrographic evidence, three distinct episodes of exoskarn garnet crystallization can be recognized, in which the fluor-hydrogarnet component steadily increased as a function of time, which probably reflects falling temperature. The REE compositions of the exoskarn minerals are regarded as having been largely inherited from the carbonate, and the exoskarn garnets increasingly fractionated HREE with time. The endoskarn and agglomerate have also been epidotized. The REE signatures of epidotes appear to be inherited partially from precursor clinopyroxenes or feldspars, which have been replaced by epidote. Late-stage vein minerals include prehnite, laumontite and K-rich laumontite, and their REE compositions appear to have been derived from the marble, probably via REE fluoro-complexes in the fluid.

Keywords

skarn mineralogyfluor-hydrogarnetsrare earth elementschalk xenolithpyroclasticsIsle of ArranScotland
Type
Geochemistry
Information
Mineralogical Magazine , Volume 51 , Issue 360 , June 1987 , pp. 231 - 246
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1987

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

Abbey, S. (1983) Geol. Surv. Can. Paper no. 83-15.Google Scholar
Alderton, D.H. M., Pearce, J.A., and Potts, P.J. (1980) Earth Planet. Sci. Lett., 49, 149-65.CrossRefGoogle Scholar
Apted, M.J. and Boettcher, A.L. (1981) Geochim. Cosmochim. Acta, 45, 827-37.CrossRefGoogle Scholar
Atkinson, W.W. Jr., Kaczmarowski, J.H., and Erickson, J. Jr. (1982) Econ. Geol., 77, 899-918.CrossRefGoogle Scholar
Burt, D.M. (1974) In Geochemical transport and kinetics W. Hofmann et al., eds.), 287-93.Google Scholar
Din, V.K. and Jones, G.C. (1978) Chem. Geol., 23, 347-52.CrossRefGoogle Scholar
Drake, M.J. (1975) Geochim. Cosmochim. Acta, 39, 55-64.CrossRefGoogle Scholar
Einaudi, M.T. and Burt, D.M. (1982) Econ. Geol., 77, 745-54.CrossRefGoogle Scholar
Meinert, L.D., and Newberry, R.J. (1981) Ibid. 75th Ann. Vol., 317-91.Google Scholar
Fleet, A.J. (1984) In Rare earth element geochemistry (P. Henderson, ed.), 343-73.Google Scholar
Gordon, T.M. and Greenwood, H.J. (1971) Am. Mineral., 56, 1674-88.Google Scholar
Greenwood, H.J. (1967) Ibid. 52, 1669-80.Google Scholar
Gunn, W. (1903) Mere. Geol. Surv. Scotl. 200 pp.Google Scholar
Gustafson, W.I. (1974) J. Petrol., 15, 455-96.CrossRefGoogle Scholar
Harris, N.B. and Einaudi, M.T. (1982) Econ. Geol., 77, 877-98.CrossRefGoogle Scholar
Henderson, P. and Williams, C.T. (1981) J. Radioanal. Chem., 67, 445-52.CrossRefGoogle Scholar
Irving, A.J. (1978) Geochim. Cosmochim. Acta, 42, 743-770.Google Scholar
Irving, A.J. and Frey, F.A. Ibid. 42, 771-85.CrossRefGoogle Scholar
King, B.C. (1954) Trans. Geol. Soc. Glasgow, 21, 440-6.CrossRefGoogle Scholar
King, B.C. (1955) Q. J. Geol. Soc. Lond., 110, 323-55.CrossRefGoogle Scholar
Kitamura, K. (1975) Econ. Geol., 70, 725-38.CrossRefGoogle Scholar
McKerrow, W.S. and Atkins, F.B. (1985) Geol. Assoc. Guide, Isle of Arran.Google Scholar
Novak, G.A. and Gibbs, G.V. (1971) Am. Mineral., 56, 791-825.Google Scholar
Pride, C., and Muecke, G.K. (1981) Contrib. Mineral. Petrol., 76, 463-71.CrossRefGoogle Scholar
Sands, C.D. and Drever, J.I. (1978) In Natural zeolites, occurrence, properties, use. (L. B. Sand and F. A. Mumpton, eds.), 26975.Google Scholar
Schnetzler, C.C. and Philpotts, J.A. (1970) Geoehim. Cosmoehim. Acta, 34, 331-40.Google Scholar
Shimazaki, H. (1969) J. Fac. Sci. Univ. Tokyo sect. 2, 17, 317-50.Google Scholar
Shoji, T. (1974) J. Mineral. Soc. Japan, 11, 359-72.Google Scholar
Shoji, T. (1975) Econ. Geol., 70, 739-49.CrossRefGoogle Scholar
Sigurdsson, H. (1977) J. Volc. Geoth. Res., 2, 165-86.CrossRefGoogle Scholar
Taylor, B.E. and Liou, J.G. (1978) Am. Mineral., 63, 378-93.Google Scholar
Tyrrell, G.W. (1928) Mere. Geol. Surv. Scotl. 292 pp.Google Scholar
Uchida, E. and Iiyama, J.T. (1982) Econ. Geol., 77, 809-22.CrossRefGoogle Scholar
Wakita, H., Rey, P, and Schmitt, R.A. (1971) Proc. 2nd Lunar Sci. Conf. 1319-29.Google Scholar
Walker, G.P. L. (1971) in Studies in Earth Sciences, West Commemoration Vol. (T. V. V. G. R. K. Murty and S. S. Rao, eds.), 181-94.Google Scholar
Williams, H. and McBirney, A.R. (1979) VolcanoIogy, 397 pp.Google Scholar