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

• Main Authors: Yasutaka Yoshimura, Yoichi Motoyoshi, Tomoharu Miyamoto, Edward S. Grew, Christopher J. Carson, Daniel J. Dunkley
• Format: Report
• Language: English
• Published: Department of Natural Environmental Science, Kochi University/National Institute of Polar Research/Department of Earth and Planetary Sciences, Kyushu University/Department of Geological Science, University of Maine/Geologcal Survey of Canada/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/?action=repository_uri&item_id=3137; http://id.nii.ac.jp/1291/00003137/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=3137&item_no=1&attribute_id=18&file_no=1

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.