Chromian Muscovites and Epidotes from Outokumpu, Finland

Peter J. Treloar1
Department of Geology and Physical Sciences, Oxford Polytechnic, Oxford OX3 0BP
1Present address: Dept. of Geology, Imperial College, London SW7 2BP.

Abstract: The Outokumpu region of Finland is notable for the large number of Cr-rich silicate and oxide phases associated with the massive sulphide deposits. In this paper analyses of Cr-rich phases in the epidote-clinozoisite and muscovite groups are presented. The muscovite-type phase shows a maximum 80% substitution of Cr for A1 on octahedral sites with a maximum 24.7 wt.% Cr2O3. Apparent complete solid solution between this extreme composition and the fuchsitic muscovites is indicated. The clinozoisite type phase has a maximum 15.4 wt.% Cr2O3, with a composition close to Ca2CrAl2Si3O12(OH). As with the micas, complete solid solution of Cr for Al in the clinozoisite structure is indicated.

Keywords: chromium • muscovite • epidote • clinozoisite • Outokumpu • Finland

Mineralogical Magazine; October 1987 v. 51; no. 62; p. 593-599; DOI: 10.1180/minmag.1987.051.362.14
© 1987, The Mineralogical Society
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