High-grade metamorphic rocks from Skallevikshalsen in the Lutzow-Holm Complex, East Antarctica: metamorphic conditions and possibility of partial melting

• Main Authors: Yoshimura, Yasutaka, Motoyoshi, Yoichi, Miyamoto, Tomoharu, Grew, Edward S., Carson, Christopher J., Dunkley, Daniel J.
• Language: English
• Published: National Institute of Polar Research 2004
• Subjects: igh-grade metamorphic rocks; mineral chemistry; partial melting; Skallevikshalsen; Lutzow-Holm Complex; East Antarctica; Antarc*; Antarctica; Polar geoscience
• Online Access: https://nipr.repo.nii.ac.jp/record/3137/files/KJ00000712294.pdf; https://doi.org/10.15094/00003137; https://nipr.repo.nii.ac.jp/records/3137

P(論文) The high-grade metamorphic rocks of Skallevikshalsen, Lutzow-Holm Complex, East Antarctica predominantly comprise garnet-sillimanite gneiss, garnet-spinel-sillimanite gneiss, garnet-biotite gneiss and garnet-two pyroxene-mafic granulite. The metamorphic conditions were estimated using various geothermometers and geobarometers for garnet-biotite gneiss and mafic gneiss. The results were 770-940℃and 0.65-1.2 GPa for garnet-biotite gneiss and 780-960℃ and 0.6-1.1 GPa for mafic gneiss. Garnet-biotite gneiss is widespread in this area and displays a well-developed migmatitic structure. Garnet porphyroblasts in the leucosome and the boundaries between leucosome and melanosome in garnet-biotite gneiss commonly have a poikiloblastic texture with euhedral feldspar and quartz inclusions. High Y concentrations in garnet cores, high An values for plagioclase inclusions, and high Ba contents in K-feldspar from garnet-biotite gneiss are inferred to reflect growth in the presence of partial melt. Garnet in garnet-sillimanite gneiss also has high Y and P contents and chemical zoning that implies changes in trace element distribution coefficients. It is suggested that hydrous melt in garnet-sillimanite gneiss was generated during prograde metamorphism while anhydrous restite underwent continuous high-temperature metamorphism. Garnet-sillimanite gneiss is likely to be the restitic product of partial melting and shows evidence for melt segregation and movement. departmental bulletin paper