Abstract
The migmatites with Kfs-poor leucosomes from the Svecofennian domain of southern Finland are characterized by a suite of anastomosing leucosome veins and patches characterized by low and varying abundance of K-feldspar with or without cordierite. These leucosomes are generated by in situ melting reactions at different P-T-aH2O conditions. Microtextural analysis in conjunction with THERMOCALC calculations and geothermobarometry show that these rocks were metamorphosed under granulite facies conditions at 700-750°C, 4-5 kbar and aH2O = 0.4-0.7. The formation of cordierite coronas around garnet and the late crystallization of andalusite suggest that the final stage of the P-T history was characterized by decompression and cooling to within the andalusite stability field, estimated at 500-650°C and 3-4 kbar. U-Pb and Sm-Nd conventional analyses of monazite and garnet, respectively, from different parts of these migmatites (mesosomes and leucosomes) indicate that, within error limits, all leucosomes were formed at about 1878 Ma during a single tectonometamorphic event. Since there is no evidence of an earlier high-grade metamorphic event in this area, it is assumed that this is the approximate age of peak metamorphism and partial melting.
Original language | English |
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Pages (from-to) | 239-253 |
Number of pages | 15 |
Journal | Geological Society Special Publication |
Volume | 168 |
DOIs | |
Publication status | Published - 2000 |
Externally published | Yes |
ASJC Scopus subject areas
- Water Science and Technology
- Ocean Engineering
- Geology