Phlogopite-chlorite reaction mechanisms and physical conditions during retrograde reactions in the Marble Formation, Franklin, New Jersey

Abstract

A retrograde assemblage in a specimen from the Franklin Marble Formation containing an unusual occurrence of three micas has been studied. Microprobe analyses of the margarite, muscovite and phlogopite reveal significant sodium and fluorine but otherwise show little mutual solid solution. The conditions that prevailed during the retrogression estimated from phase equilibria are T =370–450° C and =0.03–0.3 at an assumed pressure of 2 kb.