Emplacement of basaltic feeder dikes in limestone at Killala Bay produced grossular- and wollastonite-bearing assemblage in the aureoles of small (1.5 and 5.3m) dikes and in the outer aureole of a 50m dike, which has very high temperature assemblages in its inner aureole and which has assimilated limestone along its contact. Numerical modelling of the thermal histories of these aureoles allows them to be used as natural experiments from which kinetic parameters for the coarsening of calcite, wollastonite and quartz can be recovered. Pressure, temperature, fluid composition and fluid/rock ratio in the aureoles will be determined using stratigraphy, mineral assemblages and compositions, and thermochemical and reaction-progress calculations for buffer assemblages so that a numerical thermal history model involving multiple episodes of feeder flow, magmatic crystallization and cooling can be calibrated. Measured grain-size distributions will be use to distinguish the coarsening mechanisms of Ostwald ripening and normal grain growth, and the variation of the mean grain size with distance from the contact will be used to retrieve material constants and activation energies for grain growth. This work will "calibrate" the natural laboratory for the analysis of the kinetics of wollastonite and grossular nucleation and annealing of quartz dislocations in future studies.
