Myrmekite and Muscovite Developed by Retrograde Metamorphism at Broken Hill, New South Wales

Evan R. Phillips, D. M. Ransom and R. H. Vernon
Department of Geology, Wollongong University College, Wollongong, N.S.W.
Central Pacific Minerals N.L., Sydney, N.S.W.
School of Earth Sciences, Macquarie University, Sydney, N.S.W.

Summary: Retrograde metamorphism of gneisses and pegmatites leads in part to the destruction of feldspar and its replacement by late-stage lobate myrmekite and muscovite. Reactions promoted by retrogression suggest a range in volume of quartz production that may supplement that developed by exsolution and lead to deviations from the strict proportionality relationship suggested by previous workers. There is no need, however, to propose that quartz in myrmekite originates by constriction of pre-existing quartz within exsolved albite.

Mineralogical Magazine; March 1972 v. 38; no. 297; p. 570-578; DOI: 10.1180/minmag.1972.038.297.05
© 1972, The Mineralogical Society
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