The south-east part of the Bruffione granodiorite-intrusion is a very suitable region for investigation of mineralogical indicators of contact metamorphism. The previous regional metamorphism here was weak (T almost-equal-to 200-degrees, P almost-equal-to 2 kbar) and the contact aureole is apparently not influenced by any further large-scale intrusion episode. Average temperature distributions in the aureole were determined from mapped isograds in impure dolomites and from calcite-dolomite geothermometry. These two techniques give consistent temperature determinations in the inner part of the aureole (almost-equal-to 600-degrees-C in forsterite marbles at the contact and 500-530-degrees-C in diopside marbles at a distance of 300-600 m away from the contact). The outer limit (1000-2500 m away from the contact) of the aureole is characterized by the appearance of phlogopite. The temperature evolution in the aureole was modelled for a one-dimensional infinite intrusion using a finite element method. The average grain-size in pure dolomite marble increases systematically towards the contact. Using the results of the thermal modelling, non-isothermal grain growth was evaluated, resulting in an activation energy for grain-boundary diffusion of Q almost-equal-to 212 kJ/mol for dolomite. The contact metamorphic minerals in marls were compared with stable assemblages calculated in the system CMASH + CO2. The disposition of isograds show that, in addition to the temperature evolution, the X(CO2) content of fluid exerted a major influence on observed parageneses, The parageneses both in marls and impure dolomites were influenced by influx of H2O-rich fluids. Owing to the higher estimated permeability of marls compared to pure calcite-marbles and impure dolomites, selective infiltration of magmatic fluid during the contact metamorphism was possible.
