抄録
Manganese spinel minerals reported till now include hausmannite, iwakiite, Jacobsite, galaxite, hetaerolite, manganochromite and vuorelainenite. The first four minerals occur commonly in the bedded manganese deposits formed in Paleozoic to Mesozoic sediments of Japan. Their mutual phase relations are usually considered in the ternary system Mn3O4-MnFe2 O4-MnAl2O4. The immiscibility range between jacobsite and galaxite in the system MnFe2O4-MnAl2O4 disappears with increasing Mn3O4 content in their solid solutions at metamor. phic temperature and an extensive jacobsite∼galaxite complete solution becomes to exist with another restricted hausmannite solution in the ternary system. Jacobsite also has extensive solution with Mn2TiO4 and the Mn2TiO4 content of the solution attains to about 70 mole % in the metamorphosed deposits. Consequently jacobsite solution needs to be treated in the quarternary system Mn3O4-MnFe2O4-MnAl2O4-Mn2TiO4. Iwakiite, Mn (Fe, Mn)2O4, has the only extensive solution with Mn2TiO4 in the quarternary system but its stability relation is unknown because it never coexist with any other spinels and has not been synthesized. This mineral must hold the keys to decipher the complex phase relations in this system.
