Temperature-pressure investigation of the southern part of the Southwest Swedish granulite region
Temperature-pressure investigation of the southern part of the Southwest Swedish granulite region
European Journal of Mineralogy (February 1996) 8 (1): 51-67
Geothermometry on Fe (super 2+) -Mg exchange among coexisting garnet-clinopyroxene, garnet-orthopyroxene and garnet-hornblende indicates T for these mafic granulites and upper amphibolite facies rocks ( approximately 900 m.y.) to be in the range 700-800 degrees C and 680-750 degrees C, respectively. Estimates from Al solubility data from orthopyroxene coexisting with garnet suggest unreasonably high T. P was determined from coexisting garnet-clinopyroxene-plagioclase-quartz, garnet-orthopyroxene-plagioclase-quartz and garnet-hornblende-plagioclase-quartz parageneses; results are in the range 0.85-1.17 GPa for the granulites and 0.85-1.06 GPa for the amphibolites. A retrograde history is recorded by chemical zoning preserved as thin rims around the garnets and pyroxenes. A prograde P-T path is indicated by well-preserved coronitic textures, newly developed metamorphic pyroxenes and plagioclase in relict igneous textures, and the prograde zoning in garnet. Using the moderately Ca-rich garnets (X (sub gro) 0.17-0.29) and wide Fe-Mg range (X (sub py) 0.12-0.25), the application of different thermometers and barometers yields an apparent T and P variation up to approximately 135 degrees C and approximately 0.25 GPa.
