Mineralogical and Chemical Evolution of White Micas and Chlorites, from Diagenesis to Low-Grade Metamorphism; Data from Various Size Fractions of Greywackes (Middle Cambrian, Morocco)

E. Wybrecht, J. Duplay, A. Piqué and F. Weber
Institut de Géologie et Centre de Sédimentologie et de Géochimie de la Surface, 1 rue Blessig, 67084 Strasbourg Cedex, France

Abstract: Four size fractions have been separated and studied in eight samples of Cambrian greywackes, ranging from non-metamorphic to low metamorphic grade. Chemical study included analyses of each size fraction and comparison with the whole rock analysis. Mineralogical study involved analyses of individual crystals using microprobe (> 6 µm) and STEM (< 6 µm). This showed that in each fraction, a progressive homogenization of the mineralogical composition occurred during the development of metamorphism; that chemical transfers especially of Fe-Mg and K-Na, occurred between fine and coarse fractions and that recrystallization in fine and coarse fractions was simultaneous.

Keywords: mica • chlorite • diagenesis • metamorphism • greywackes • Morocco • Cambrian

Mineralogical Magazine; June 1985 v. 49; no. 352; p. 401-411; DOI: 10.1180/minmag.1985.049.352.11
© 1985, The Mineralogical Society
Mineralogical Society (www.minersoc.org)