Bleaching of limestones in the Notch Peak contact-metamorphic aureole, Utah

Where dark-colored limestone is "bleached" to white, the composition of metamorphic fluids can be constrained. Dark-blue limestone layers that have a carbon phase comprising 0.04 + or -0.02 wt% of the rock were bleached during contact metamorphism by a neighboring quartz monzonite. Fluids responsible for the bleaching must have been >90% water, on the basis of graphite-C-O-H fluid interactions.Mathematical modeling indicates that diffusion of a water-rich fluid through pores or along fluid films on grain edges could complete the observed bleaching, if it is assumed that the diffusion coefficient of water is greater than 10 (super -15) .