四国西部肱川地域の秩父帯北帯における含黒雲母塩基性準片岩 [in Japanese] Biotite-bearing basic semischists from the northern Chichibu belt in the Hijikawa district, western Shikoku, Japan [in Japanese]
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Metamorphic biotites have been found from the pumpellyite-actinolite facies basic semischists in the northern Chichibu Belt, western Shikoku, Japan. Representative mineral assemblages of the northern Chichibu basic semischists in the study area are chlorite+phengite+calcite, riebeckite+phengite+chlorite+calcite, riebeckite+stilpnomerane+chlorite+calcite, biotite+riebeckite+chlorite+calcite and biotite+riebeckite+phengite+chlorite+calcite. Albite, titanite, hematite and quartz are common. The biotites occur in high-MgO basic semischists and are rich in phlogopite content. The mineral parageneses systematically change depending on MgO/(MgO+FeO) of bulk compositions.<br> The bioitite-calcite-bearing basic semischists were metasomatically altered based on petrographical and geochemical data. The isocon diagram suggests that CaO and MgO were added in significant amounts and Na<sub>2</sub>O, K<sub>2</sub>O and P<sub>2</sub>O<sub>5</sub> were removed. It seems that the increase in MgO due to metasomatism is a cause of the formation of biotite under the pumpellyite-actinolite facies.
- Journal of Mineralogical and Petrological Sciences
Journal of Mineralogical and Petrological Sciences 93(8), 291-306, 1998-08-05
Japan Association of Mineralogical Sciences