Hornblende gneisses from Syowa Station, East Antarctica

• Main Authors: Yoshikuni Hiroi, Hitoshi Onuki
• Format: Report
• Language: English
• Published: Department of Earth Sciences, Faculty of Science, Chiba University 1985
• Subjects: East Antarctica; Syowa Station; Antarc*; Antarctica; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=1785; http://id.nii.ac.jp/1291/00001785/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=1785&item_no=1&attribute_id=18&file_no=1

Pyroxene gneiss (charnockitic gneiss), local hornblende gneiss (bleached part of pyroxene gneiss), biotite schist, and pegmatite were newly analyzed chemically. The results together with the published analyses of regional hornblende gneisses and pyroxene gneisses show that regional hornblende gneisses generally have higher rock oxidation ratios and MgO/(MgO+FeO) ratios than pyroxene gneisses and local hornblende gneiss, in harmony with the differences in oxide mineral assemblages and in microprobe analyses of minerals. Such differences correspond to the factors controlling the stabilities of amphiboles, and suggest that regional hornblende gneisses are the products of low granulite-facies metamorphism. The difference in mineralogy among pyroxene gneiss, local hornblende gneiss, and biotite schist may be shown by an isochemical reaction.