Abstract

Partial electron microprobe analyses of muscovite from 32 Puzzle Mountain (Maine) meta pelites reveal that paragonite (Pg) content systematically decreases from the lower sillimanite zone (LSZ) to the upper sillimanite zone (USZ) whereas TiO2 content increases. The average mole percent Pg in either muscovite megacrysts or pseudomorphs after staurolite is 21.6 (LSZ) and 18.3 (usz); groundmass muscovites average 21.7 (LSZ) and 18.6 (USZ). Weight percent TiO2 in these muscovites averages 0.61 (LSZ psuedomorphs), 0.62 (LSZ groundmass), and 0.75 (for usz pseudomorphs as well as groundmass). The virtual identity in Pg and TiO2 contents for the groundmass and the pseudomorph muscovite in each metamorphic environment supports Guidotti’s (1968) suggestion that muscovite pseudomorphs after staurolite are equilibrium features of prograde metamorphism.

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