David R. Wones

Mica polytypes: Systematic description and identification

X-ray studies of mica specimens from a variety of geological localities show that biotite and certain lithium-rich mica samples are composed of a mixture of different polytypes. Many of the biotite structures are new complex polytypes not before reported. A new method of designating mica polytypes is proposed. Techniques are described for the systematic generation of all the possible layer-stacking sequences of mica polytypes and for the verification of the stacking sequences in newly discovered forms.

The Stability of Phlogopite in the Presence of Quartz and Diopside

The stability of phlogopite in the presence of quartz and diopside is of interest in the interpretation of biotite-bearing assemblages in granitic rocks and of biotite-clinopyroxene-amphibole assemblages in metamorphic rocks. This study, begun to compliment the studies of Luth (1967), Schairer (1954), and Shaw (1963), is now being abandoned and the results to date are presented herein. Numerous persons have contributed to the study. Starting materials were contributed by W.T. Pecora, J.F. Schairer, and H.S. Yoder. Laboratory assistance was provided by J.V. Chernosky, C.J. Duffy, H.R. Shaw, and J. Whitney. N. Chatterjee, W.C. Luth, and D.A. Hewitt discussed many aspects of the theoretical and applied aspects of the study. J.S. Huebner and M.E. Woodruff were particularly helpful in the acquisition of x-ray powder intensity data. J.V. Chernosky provided library access and working space at the Univ. of Maine, Orono, so that this manuscript could be finished in the midst of an active field season. Critical reviews by J.S. Huebner, R.A. Robie, D.B. Stewart and E-an Zen helped to improve the manuscript.

A low pressure investigation of the stability of phlogopite

Abstract Phlogopite reacts to form orthorhombic kalsilite, leucite, forsterite and fluid (H2O) at 1012 ± 7°C, 400 bars pressure, and 905 ± 5°C at 100 bars pressure. The heat of reaction is 39 ± 4 kcal compared to 44 ± 6kcal for the reaction of annite to form orthorhombic kalsilite, leueite, fayalite and fluid (H2O). The results are consistent with earlier experiments, but not with the interpretations of those experiments.