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The influence of secondary alteration on the ammonium content of granites, exemplified by the Rosses complex of Donegal

Published online by Cambridge University Press:  05 July 2018

A. Hall
A. Hall*
Affiliation:
Department of Geology, Royal Holloway College, Egham, Surrey TW20 0EX
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Abstract

Ammonium analyses of representative rocks from the Rosses granite complex (Ireland) and their constituent mineral show that any variation of magmatic origin has been completely obscured by pervasive hydrothermal alteration. The altered rocks are strongly enriched in the ammonium ion, most of which is held by chloritized biotite and sericitized plagioclase. The present ammonium content of the Rosses granites averages 13 ppm, but the original ammonium content of the magmas is estimated to have been less than 5 ppm. Potassium feldspars may preserve a better record of the original magmatic ammonium content than the whole rocks or the biotites.

Keywords

ammoniumRosses complexIrelandgranitesecondary alteration
Type
Geochemistry and Petrology
Information
Mineralogical Magazine , Volume 57 , Issue 389 , December 1993 , pp. 591 - 598
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1993

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References

Burke, K. C., Cunningham, M. A., Gallagher, M. J., and Hawkes, J. R. (1964) Beryl in the Rosses granite, north-west Ireland. Econ. Geol., 59, 1539–50.Google Scholar
Cooper, D. C. and Bradley, A. D. (1990) The ammonium content of granites in the English Lake District. Geol. Mag., 127, 579–86.Google Scholar
Hall, A. (1966a) A petrogenetic study of the Rosses granite complex, Donegal. J. Petrol., 7, 202–20.Google Scholar
Hall, A. (1966b) The feldspars of the Rosses granite complex, Donegal, Ireland. Mineral. Mag., 35, 975–82.Google Scholar
Hall, A. (1969) The micas of the Rosses granite complex, Donegal. Sci. Proc. Roy. Dublin Soc., 3A, 209-17.Google Scholar
Hall, A. (1987) The ammonium content of Caledonian granites. J. Geol. Soc. Lond., 144, 671–4.Google Scholar
Hall, A. (1988) The distribution of ammonium in the granites of south-west England. Ibid. 145, 37-41.Google Scholar
Hall, A. (1993) Application of the indophenol blue method to the determination of ammonium in silicate rocks and minerals. Appl. Geochem., 8, 101–5.Google Scholar
Hall, A. Bencini, A., and Poli, G. (1991) Magmatic and hydrothermal ammonium in granites of the Tuscan magmatic province, Italy. Geochim. Cosmochim. Acta, 55, 3657–64.Google Scholar
Honma, H. and Itihara, Y. (1981) Distribution of ammonium in minerals of metamorphic and granitic rocks. Ibid. 45, 983-8.Google Scholar
Krohn, M. D. and Altaner, S. P. (1987) Near-infrared detection of ammonium minerals. Geophysics, 52, 924–30.Google Scholar
Mercy, E. L. P. (1960) The geochemistry of the Rosses granitic ring complex, Co. Donegal, Ireland. Trans. Roy. Soe. Edinburgh, 64, 128–38.Google Scholar
Pitcher, W. S. (1953) The Rosses granitic ring complex, country Donegal, Eire. Proc. Geol. Assoc. (London), 64, 153–82.Google Scholar
Pitcher, W. S. and Berger, A. R. (1972) The geology of Donegal: study, of granite emplacement and unroofing. Wiley-Interscience, New York and London.Google Scholar
Ridgway, J., Appleton, J. D., and Levinson, A. A. (1990) Ammonium geochemistry in mineral exploration-a comparison of results from the American Cordilleras and the southwest Pacific. Appl. Geochem., 5, 475-89.Google Scholar
Wells, A. F. (1984) Structural inorganic chemistry. 5th edition. Clarendon Press, Oxford.Google Scholar
Wlotzka, F. (1972) Nitrogen. In: Handbook of Geochemistry ( K. H. Wedepohl ed.) Vol. II, chapter 7BO, Springer-Verlag.Google Scholar