Mass transfer during Barrovian metamorphism of pelites, south- central Connecticut. I: evidence for changes in composition and volume

Abstract

Evidence for mass and volume changes attending the Barrovian (chlorite to kyanite zone) metamorphism of aluminous pelites of the Wepawaug Schist, Connecticut, is examined using a petrologic mass balance approach that takes full account of the closure problem and the multivariate nature of compositional data. Statistical analysis and regional mapping of chemistry and density variations strongly suggest that the physicochemical properties of the pelites are correlated with geographic position and metamorphic grade. The nature and degree of the variations indicate that they are the result of metamorphism, not sedimentary or diagenetic processes. Mass balance analysis strongly suggests that metamorphism led to significant mass and volume changes over minimum length scales on the order of typical hand sample dimensions. The results of this study indicate that significant, heretofore unrecognized changes in the composition and volume of aluminous pelite may occur during Barrovian style metamorphism. -from Author