島根大学理学部紀要

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島根大学理学部紀要 19
1985-12-25 発行

離溶により生じた単斜シソ輝石母体の結晶構造について

On the Structure of Clinohypersthene Derived as a Host Phase from Parental Pigeonite by Exsolution
山口 佳昭
冨田 克敏
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内容記述(抄録等)
Structure refinement was made for a clinohypersthene C_<.02> Mg_<.51> Fe_<.47> Si_20_6, derived as a host phase from parental pigeonite by exsolution of augite along the metastable extension of the pigeonite solvus into the stability field of hypersthene. The particular characteristics of the structure are discussed, and compared with those of pigeonite and orthohypersthene. The clinohypersthene shows no indication of anti-phase domain structure on the reflections with (h+k) odd, and has six-fold coordination of oxygen around M2 site. Clino- and orthopyroxenes of hypersthene composition have closely similar atomic parameters. Kinetic factors are expected to be strongly responsible for the metastable extension of the pigeonite solvus.