Layer Silicates from Serpentinite-Pegmatite Contact (Wiry, Lower Silesia, Poland)

J. Jelitto1, E. Dubińska1, A. Wiewióra2 and P. Bylina2
1 Institute of Geochemistry, Mineralogy and Petrography, Faculty of Geology Warsaw University, Żwirki i Wigury 93, 02-089 Warsaw, Poland
2 Institute of Geological Sciences, Polish Academy of Sciences Ÿwirki i Wigury 93, 02-089 Warsaw, Poland

Abstract: Highly tectonized contact between serpentinite and younger pegmatite in the magnesite mine of Wiry contains various layer silicates. Vermiculite, chlorite, smectite, and interstratified mica-vermiculite were recognized by means of routine XRD examination. Two three component interstratifications of mica-vermiculite-chlorite and chlorite-swelling chlorite-smectite were identified by a combined procedure of deconvolution of the XRD patterns and simulation of XRD tracings. A mineral with large diffraction maxima, displaying “chlorite intergrade” characteristics, appeared to be a mixture of chlorite, mixed layer chlorite-smectite, and vermiculite. Polytypes of phyllosilicates were determined by the X-ray transmission method. Due to the heritage of parent mineral polytype structure by transitional products of alteration, two distinct sequences of layer silicates were observed: one formed from trioctahedral mica (vermiculite, mixed layer mica-vermiculite); and one evolved from chlorite (e.g., mixed layer chlorite-swelling chloritesmectite). A tentative scheme of the primary contact zone structure, not obscured by subsequent brittle tectonics either by transformation of layer silicates, is proposed.

Key Words: Chlorite • Intergrade • Mica • SEM • Serpentinite/pegmatite contact • Three component interstratified minerals • Vermiculite • Weathering • X-ray powder

Clays and Clay Minerals; December 1993 v. 41; no. 6; p. 693-701; DOI: 10.1346/CCMN.1993.0410607
© 1993, The Clay Minerals Society
Clay Minerals Society (www.clays.org)