THE EFFECT OF THERMAL HISTORY ON THE DEVELOPMENT OF MINERAL ASSEMBLAGES DURING INFILTRATION-DRIVEN CONTACT-METAMORPHISM

A one-dimensional model for coupled heat flow, fluid flow, and mineral reaction predicts the identity and spatial and temporal distributions of mineral assemblages produced during contact metamorphism of silice ous dolomite. Results are compared to mineral distributions predicted by transport models for fluid flow along steady-state temperature prof iles and to mineral distributions observed in contact aureoles to asse ss whether a detailed analysis of heat flow is required to extract mea ningful information of fluid flow history from field data. Results ide ntify several mineral assemblages whose interpretation in terms of flu id flow is dependent on an understanding of their thermal history. Cer tain key mineral assemblages, however, are sensitive records of the ge ometry and amount of fluid flow but are insensitive to thermal history . The presence or absence of these mineral assemblages constrains the history of fluid flow during contact metamorphism of siliceous dolomit e regardless of the details of heat flow. Occurrences of the key assem blages record both magmatic fluid flow in the direction of decreasing temperature (Alta, Elkhorn aureoles) and metamorphic fluid flow in the direction of increasing temperature (Beinn an Dubhaich, Kasuga-mura a ureoles) during contact metamorphism. Time-integrated input fluid flux averages on the order of 100 mol/cm(2) with a range of +/-1 order of magnitude.