Amphibolite-facies mineral assemblages in the Belgica Mountains, East Antarctica

• Main Authors: Masao Asami, Hideyasu Kojima, Keizo Yanai, Tamio Nishida
• Format: Report
• Language: English
• Published: Department of Geological Sciences, College of Liberal Arts, Okayama University/National Institute of Polar Research/National Institute of Polar Research/Institute of Earth Science, Faculty of Education, Saga University 1986
• Subjects: Belgica Mountains; Belgica, Mountains; East Antarctica; Yamato; Antarc*; Antarctica; Memoirs of National Institute of Polar Research; Polar Research
• Online Access: https://nipr.repo.nii.ac.jp/?action=repository_uri&item_id=2016; http://id.nii.ac.jp/1291/00002016/; https://nipr.repo.nii.ac.jp/?action=repository_action_common_download&item_id=2016&item_no=1&attribute_id=18&file_no=1

As the first petrological study of metamorphism in the Belgica Mountains, East Antarctica, mineral assemblages of the metamorphics of various compositions are examined and the metamorphic conditions are preliminarily estimated. The amphibolite-facies metamorphism is indicated by the mineral assemblages. Besides the occurrence of clinohumite and chondrodite in dolomitic marble, the following features are characteristic of the assemblages : the absence of garnet in metabasites and the presence of the calcite-quartz and Ca-garnet-quartz associations and no wollastonite in calcareous rocks. The garnet-biotite thermometry gives the metamorphic temperatures of 680-700℃. The five-phase assemblage forsterite-tremolite-dolomite-calcite-spinel in dolomitic marble is noted for a fluid pressure estimate in this rock. Total fluid pressures around 5kb at 680-700℃ are obtained from the experimental equilibrium relations concerning the five-phase assemblage (P.METZ : Contrib. Mineral. Petrol., 58,137,1976; J. M. RICE : Contrib. Mineral. Petrol., 59,237,1977; H.-R. KASE and P. METZ : Contrib. Mineral. Petrol., 73,151,1980). If P_<solid>=P_<fluid> is assumed, the metamorphism would be of relatively low pressure just like that in the Yamato Mountains which are situated about 200km northeast of the Belgica Mountains.