POLYMETAMORPHISM IN THE LAPLAND GRANULITE BELT - EVIDENCE FROM FLUID INCLUSIONS

Fluid inclusions were studied in the Lapland granulites and the underl ying rocks of Korva Tundra (a part of the Tanaelv Complex). According to mineralogical thermobarometry data, the Lapland granulites were met amorphosed in four stages (M1 - M4); the lower grade Korva Tundra meta morphic rocks were progradely metamorphosed during a single stage. Sev eral populations of fluid inclusions recognized in the Lapland granuli tes differ in their chemistries (detected using their melting temperat ures) and densities (calculated from the homogenization temperatures). These groups of fluid inclusions were correlated with metamorphic M1 - M4 stages. The metamorphic processes of the first two stages can be recognized only in occasional relies; the N-2 + CH4 (M1) and CO2 + CH4 (N-2)+ H2O (M2) inclusions are also relict. The later M3 and M4 metamo rphic stages occurred in the presence of an aqueous-carbon dioxide flu id: X(H2O) = 0.25 - 0.41 during the M3 stage and 0.30 - 0.44 during th e M4 stage. The Korva Tundra rocks were metamorphosed in the presence of a simpler aqueous-carbon dioxide fluid, X(H2O) = 0.50 - 0.58, which is consistent with their monocyclic metamorphism.