Chlorine-Rich Potassium Hastingsite from West Ongul Island, Lützow-Holm Bay, East Antarctica

Kanenori Suwa, Masaki Enami and Tatsuro Horiuchi
Department of Earth Sciences, Faculty of Science, Nagoya University, Chikusa-ku, Nagoya 464, Japan

Abstract: Chlorine-rich potassium hastingsite occurs in a calcareous pegmatite, a replacement zone and an amphibolite lens within hornblende gneiss on West Ongul Island, Lützow-Holm Bay, East Antarctica. The amphibolite lens and hornblende gneiss were metamorphosed to the kyanite-sillimanite grade of the granulite facies during Proterozoic metamorphism. Chemical analysis (3.27 wt.% Cl), unit cell parameters and optical properties of the Cl-rich potassium hastingsite are given. Cl-rich (> 3 wt.%) calcic amphiboles reported from various rock types are mostly more than 0.9 in (Na+ K) content, more than 0.4 in K/(Na + K) ratio, more than 0.75 in Fe2+/(Fe2+ + Mg + Mn) ratio and more than 1.9 in AlIV content (total iron as FeO and O = 23). The unit cell volume of Cl-rich hastingsite is distinctly larger than that of Cl-poor hastingsite.

Keywords: Cl-rich calcic amphiboles • hastingsite • West Ongul Island • Antarctica

Mineralogical Magazine; December 1987 v. 51; no. 363; p. 709-714; DOI: 10.1180/minmag.1987.051.363.11
© 1987, The Mineralogical Society
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