Orthopyroxene-bearing rocks from the Tenmondai and Naga-iwa Rocks in the Prince Olav Coast, East Antarctica: First appearance of orthopyroxene in progressive metamorphic sequence

• Main Authors: Kazuyuki Shiraishi, Yoshikuni Hiroi, Hitoshi Onuki
• Format: Report
• Language: English
• Published: National Institute of Polar Research/Institute of Earth Science, Faculty of Education, Kanazawa University/Department of Earth Sciences, Faculty of Science, Hirosaki University 1984
• Subjects: East Antarctica; Prince Olav Coast; Naga-iwa; Antarc*; Antarctica; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=1647; http://id.nii.ac.jp/1291/00001647/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=1647&item_no=1&attribute_id=18&file_no=1

Orthopyroxene first appears in the Tenmondai and Naga-iwa Rocks in the progressive metamorphic sequence of the kyanite-sillimanite type from northeast to southwest along the Prince Olav and Soya Coasts, East Antarctica. Field occurrence and detailed petrography of three orthopyroxene-bearing rocks from the bedrock exposures are presented in this paper. The mineral compositions as well as mineral textures suggest that the rocks are close to chemical equilibrium, that orthopyroxene was first produced in such manner (order) as is predicted experimentally and theoretically, and that the chemical compositions of the calcic amphiboles coexisting with orthopyroxene can be indicators of metamorphic grade.