Hi all. I received many excellent responses to my query below. To
summarize, this assemblage (Bt-absent Ms+Cld+Chl+Als) is well documented in
both the kyanite and andalusite fields, in a couple cases straddling the
Ky-And boundary (Mengel & Rivers, Can Min 1994; forthcoming paper by Pentti
Holtta and co-authors), but never in the Sil field. The assemblage is
likely terminated by the CldAls=StChl reaction, which occurs at lower
temperature than the Al2SiO5 invariant pt. (eg, in grids of Spear & Cheney
1989; Powell & Holland 1990).
David R.M. Pattison, Department of Geology and Geophysics,
University of Calgary, Calgary, Alberta, T2N 1N4, Canada.
Phone: 403-220-3263 (my office); 403-220-5841 (dept. office)
Fax: 403-284-0074 email: [log in to unmask]