岩手県宮古市根市鉱山産苦灰岩大理石中のゲイキ石, バデレイ石およびジルコノライト

概要

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Microprobe study on geikielite in dolomitic marble from the Neichi mine, Iwate Prefecture, described by Watanabe et al. (1963) informed it to be zoned with low MgO rim. The analyses of core and rim are : MgO 20.10,15.23; FeO 12.69,15.98; MnO 6.04,8.66; Cao 0.40,0.29; TiO_2 61.44,59.31; totals 100.67,99.47%, respectively. Their empirical formulae (basis : O=3) are : (Mg_<0.65> Fe_<0.23> Mn_<0.11> Ca_<0.01>)_<Σ1.00> Ti_<1.00>O_3 and (Mg_<0.51> Fe_<0.30>Mn_<0.17> Ca_<0.01>)_<Σ0.99> Ti_<1.01>O_3,respectively. Manganese and iron are remarkably high relative to the associated spinel and forsterite. Also, baddeleyite, zirconolite and zircon are found as its close associates, the second being the first find in Japan. All of them are so close to their ideal formulae as represented by zirconolite. The chemical analysis gave CaO 16.41,TiO_2 45.87,FeO^*0.76,ZrO_2 36.56,total 99.60%. The empirical formula (basis : O=7,FeO^*as Fe_2O_3)is Ca_<1.00>(Ti_<1.97> Fe_<0.04>)_<Σ2.01> Zr_<1.02>O_7,thus, the material is extremely poor in the non-essential components, which are always contained in zirconolites of igneous origin.
国立科学博物館の論文