岩手県上乙茂産花崗岩ペグマタイト中の含カルシウムチロディ閃石の産出

概要

論文の詳細を見る
A clinoamphibole from the granite pegmatite of Kamiotomo. Iwaizumimachi, Iwate Prefecture, is found to be a calcian tirodite, (Mn_<1.59>Ca_<0.54>Mg_<3.02>Fe_<1.83>Al_<0.10>)_<Σ7.08>(Si_<7.74>Al_<0.26>)_<Σ8.00>O_<23> on the basis of O=23. This is a rare example of the occurrence of such a high magnesium ferromagnesian mineral in a granite pegmatite. The associated minerals include pyroxmangite ((Mn_<0.62>Fe_<0.22>Mg_<0.12>Ca_<0.05>)_<Σ1.01>Si_<0.99>)O_3). The assemblage of tirodite and pyroxmangite both compositionally close to above case is also found in a contact metamorphosed manganese ore from Zomeki deposit of the Kusugi mine, Yamaguchi Prefecture. The 2/7 boundary for (Mn+Ca) contents of these Mg-Fe-Mn clinoamphiboles is extant despite the co-existence with pyroxmangite. One of the materials on 2.5/7 boundary of Nambu et al. (1980) occurs as veinlets cutting a wallrock of manganese ore, i.e., in the different mode of occurrence from the present case.
国立科学博物館の論文