RELICT SAPPHIRINE IN PYROPIC GARNET FROM THE EASTERN SØR RONDANE MOUNTAINS, ANTARCTICA
Sapphirine-bearing biotitic schist forms a reaction zone between an ultramafic lens and its host biotite-hornblende gneiss at Balchenfjella, which is underlain by migmatitic complex metamorphosed under granulite-facies conditions in the Late Proterozoic and under amphibolite-facies conditions in the...
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ftnipr:oai:nipr.repo.nii.ac.jp:00002765 2023-05-15T13:49:00+02:00 RELICT SAPPHIRINE IN PYROPIC GARNET FROM THE EASTERN SØR RONDANE MOUNTAINS, ANTARCTICA アサミ マサオ マキモト ヒロシ / Masao ASAMI Hiroshi MAKIMOTO Edward S. GREW 1994-09 https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2765 http://id.nii.ac.jp/1291/00002765/ https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2765&item_no=1&attribute_id=18&file_no=1 en eng ABSTRACT Department of Geological Sciences, College of Liberal Arts, Okayama, University Geological Survey of Japan Department of Geological Sciences, University of Maine National Institute of Polar Research https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2765 http://id.nii.ac.jp/1291/00002765/ AA1072335X Proceedings of the NIPR Symposium on Antarctic Geosciences, 7, 179(1994-09) https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2765&item_no=1&attribute_id=18&file_no=1 Departmental Bulletin Paper P(論文) 1994 ftnipr 2022-11-26T19:42:11Z Sapphirine-bearing biotitic schist forms a reaction zone between an ultramafic lens and its host biotite-hornblende gneiss at Balchenfjella, which is underlain by migmatitic complex metamorphosed under granulite-facies conditions in the Late Proterozoic and under amphibolite-facies conditions in the Early Paleozoic. This schist consists of porphyroblastic garnet, the core of which is compositionally homogeneous pyrope-almandine (X_<Mg>=Mg/(Fe+Mg)≅0.50) surrounded by an almandine rim (X_<Mg>≅0.27), biotite (X_<Mg>=0.70-0.73), plagioclase (An_<75-87>), spinel (X_<Mg>=0.26-0.36), corundum, rutile and zircon. In addition, individual garnet porphyroblasts enclose different mineral associations in the magnesian cores as follows : (A) sapphirine (X_<Mg>=0.75-0.85), commonly with kyanite, and, locally, with spinel (X_<Mg>=0.50-0.68), (B) kyanite only, and (C) gedrite (X_<Mg>=0.75-0.78)+quartz aggregates. The mineral associations sapphirine+kyanite±spinel and gedrite+quartz±kyanite are inferred to be relict assemblages of the prograde P-T path, and the magnesian garnet cores to have been homogenized during the granulite-facies event. Differences in the associations are presumed to have resulted from pre-metamorphic chemical heterogeneity in the precursor to the biotitic schist. These mineral associations suggest a clockwise prograde P-T trajectory entirely within the kyanite field; the assemblage sapphirine+kyanite might have been stable as T approached 700℃ constraining P to be at least 8 kbar. Further increase in temperature was accompanied by a small decrease in P to the 7-8 kbar (at T=760-800℃) estimated for peak conditions in the granulite-facies by M. ASAMI et al. (Proc. NIPR Symp. Antarct. Geosci., 6,57,1993). The relict sapphirine-kyanite assemblages in the Sør Rondane Mountains are similar to those reported from the Luzow-Holm Bay complex, Antarctica, and the Highland Complex, Sri Lanka (e.g. Y. OGO et al. : Recent Progress in Antarctic Earth Science, ed. by Y. ... Report Antarc* Antarctic Antarctica National Institute of Polar Research Repository, Japan Antarctic Sør-Rondane ENVELOPE(25.000,25.000,-72.000,-72.000) Sør Rondane Mountains ENVELOPE(25.000,25.000,-72.000,-72.000) Balchenfjella ENVELOPE(27.200,27.200,-72.000,-72.000) |
institution |
Open Polar |
collection |
National Institute of Polar Research Repository, Japan |
op_collection_id |
ftnipr |
language |
English |
description |
Sapphirine-bearing biotitic schist forms a reaction zone between an ultramafic lens and its host biotite-hornblende gneiss at Balchenfjella, which is underlain by migmatitic complex metamorphosed under granulite-facies conditions in the Late Proterozoic and under amphibolite-facies conditions in the Early Paleozoic. This schist consists of porphyroblastic garnet, the core of which is compositionally homogeneous pyrope-almandine (X_<Mg>=Mg/(Fe+Mg)≅0.50) surrounded by an almandine rim (X_<Mg>≅0.27), biotite (X_<Mg>=0.70-0.73), plagioclase (An_<75-87>), spinel (X_<Mg>=0.26-0.36), corundum, rutile and zircon. In addition, individual garnet porphyroblasts enclose different mineral associations in the magnesian cores as follows : (A) sapphirine (X_<Mg>=0.75-0.85), commonly with kyanite, and, locally, with spinel (X_<Mg>=0.50-0.68), (B) kyanite only, and (C) gedrite (X_<Mg>=0.75-0.78)+quartz aggregates. The mineral associations sapphirine+kyanite±spinel and gedrite+quartz±kyanite are inferred to be relict assemblages of the prograde P-T path, and the magnesian garnet cores to have been homogenized during the granulite-facies event. Differences in the associations are presumed to have resulted from pre-metamorphic chemical heterogeneity in the precursor to the biotitic schist. These mineral associations suggest a clockwise prograde P-T trajectory entirely within the kyanite field; the assemblage sapphirine+kyanite might have been stable as T approached 700℃ constraining P to be at least 8 kbar. Further increase in temperature was accompanied by a small decrease in P to the 7-8 kbar (at T=760-800℃) estimated for peak conditions in the granulite-facies by M. ASAMI et al. (Proc. NIPR Symp. Antarct. Geosci., 6,57,1993). The relict sapphirine-kyanite assemblages in the Sør Rondane Mountains are similar to those reported from the Luzow-Holm Bay complex, Antarctica, and the Highland Complex, Sri Lanka (e.g. Y. OGO et al. : Recent Progress in Antarctic Earth Science, ed. by Y. ... |
format |
Report |
author |
アサミ マサオ マキモト ヒロシ / Masao ASAMI Hiroshi MAKIMOTO Edward S. GREW |
spellingShingle |
アサミ マサオ マキモト ヒロシ / Masao ASAMI Hiroshi MAKIMOTO Edward S. GREW RELICT SAPPHIRINE IN PYROPIC GARNET FROM THE EASTERN SØR RONDANE MOUNTAINS, ANTARCTICA |
author_facet |
アサミ マサオ マキモト ヒロシ / Masao ASAMI Hiroshi MAKIMOTO Edward S. GREW |
author_sort |
アサミ マサオ |
title |
RELICT SAPPHIRINE IN PYROPIC GARNET FROM THE EASTERN SØR RONDANE MOUNTAINS, ANTARCTICA |
title_short |
RELICT SAPPHIRINE IN PYROPIC GARNET FROM THE EASTERN SØR RONDANE MOUNTAINS, ANTARCTICA |
title_full |
RELICT SAPPHIRINE IN PYROPIC GARNET FROM THE EASTERN SØR RONDANE MOUNTAINS, ANTARCTICA |
title_fullStr |
RELICT SAPPHIRINE IN PYROPIC GARNET FROM THE EASTERN SØR RONDANE MOUNTAINS, ANTARCTICA |
title_full_unstemmed |
RELICT SAPPHIRINE IN PYROPIC GARNET FROM THE EASTERN SØR RONDANE MOUNTAINS, ANTARCTICA |
title_sort |
relict sapphirine in pyropic garnet from the eastern sør rondane mountains, antarctica |
publisher |
ABSTRACT |
publishDate |
1994 |
url |
https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2765 http://id.nii.ac.jp/1291/00002765/ https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2765&item_no=1&attribute_id=18&file_no=1 |
long_lat |
ENVELOPE(25.000,25.000,-72.000,-72.000) ENVELOPE(25.000,25.000,-72.000,-72.000) ENVELOPE(27.200,27.200,-72.000,-72.000) |
geographic |
Antarctic Sør-Rondane Sør Rondane Mountains Balchenfjella |
geographic_facet |
Antarctic Sør-Rondane Sør Rondane Mountains Balchenfjella |
genre |
Antarc* Antarctic Antarctica |
genre_facet |
Antarc* Antarctic Antarctica |
op_relation |
https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2765 http://id.nii.ac.jp/1291/00002765/ AA1072335X Proceedings of the NIPR Symposium on Antarctic Geosciences, 7, 179(1994-09) https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2765&item_no=1&attribute_id=18&file_no=1 |
_version_ |
1766250309542215680 |