Sudoite, Al-rich Li-Mg-bearing chlorite, clinochlore and kaolinite as alteration products of biotite in Visean K-bentonites from Belgium
European Journal of Mineralogy Volume 8 Number 3 (1996), p. 493 - 506
published: Jun 17, 1996
manuscript accepted: Feb 2, 1996
manuscript received: Nov 7, 1994
ArtNo. ESP147050803004, Price: 29.00 €
Abstract Optical microscopy, X-ray diffraction, electron and ion microprobe analyses have been performed to study alteration products of biotite flakes occurring in some Visean K-bentonites from Belgium. Alteration has induced bleaching and swelling of the flakes. The former biotites now are partially or totally colourless with low birefringence and contain chlorites or kaolinite. Two types of Al-rich chlorites have been identified: sudoite and an Li-Mg-bearing chlorite chemically intermediate between sudoite, cookeite and donbassite. Clinochlore is rarely present. The bulk-rock Li contents, up to 0.28 wt.% Li2O, are considered as a geochemical tracer of magmatic origin.