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Free University, Amsterdam, The Netherlands
In granulites, which constitute a major, if not exclusive rock type of the lower continental crust, fluid inclusions are abundant in many rock-forming minerals. Most contain a characteristic ‘carbonic’ fluid, high density CO2 possibly mixed with variable quantities of N2 and more rarely, CH4 · NaCl brine inclusions have recently been observed in metasedimentary granulites from southern Norway. P-T estimates from synmetamorphic pure CO2 inclusions agree with solid mineral thermobarometry in three selected examples of: (a) high-pressure granulites (Fura Complex, Tanzania), (b) intermediate-pressure granulites (southern Karnataka, India) and (c) low-pressure granulites (West Uusimaa Complex, Finland). These data support a model of fluid distribution of the lower crust based on the predominance of density-controlled, mantle-derived CO2-rich fluids coexisting immiscibly with NaCl brines. In southern Norway, most of the CO2 was associated with or derived from carbonate-rich melts emplaced with deep seated, intermediate synmetamorphic intrusives.
