Amphiboles in the Lilloise Intrusion, East Greenland

P. E. Brown, F. E. Tocher and A. D. Chambers
Department of Geology and Mineralogy, The University, Aberdeen AB9 1AS
Department of Geological Sciences, University of Aston, Birmingham B4 7ET

Abstract: Amphibole in the lower parts of the Lilloise layered intrusion occurs interstitially and as a replacement of pyroxene; in the upper rocks it is a major cumulus phase. There is an overall trend of increasing Fe/(Fe + Mg) with height. Coupled substitutions which effect the variation in composition of the amphiboles are chiefly Na,K(A)+Al(T) for □A+SiT) and Ti+Al(T) for Fe3+(C)+ Si(T). There is considerable variation in composition both on the specimen scale and within individual grains. This variation, plus scatter found in plots of the coupled substitutions, is partly attributed to many of the amphiboles having replaced pyroxene and also to the effects of magmatic-hydrothermal fluids.

Mineralogical Magazine; 1982 v. 45; no. 337; p. 47-54; DOI: 10.1180/minmag.1982.045.337.05
© 1982, The Mineralogical Society
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