Chemical composition of regularly interstratified chlorite/smectite in the ores from some Neo-gene gold-silver vein-type deposits in Japan

Chemical composition of regularly interstratified chlorite/smectite in the ores from some Neogene gold-silver vein-type deposits in Japan.By Tetsuro YONEDA** and Takashi WATANABE*** Abstract: Regularly interstratified chlorite/smectite mineral occurs widely as a gangue mineral in epithermal goldsilver-quartz veins, associated closely with base-metal sulfides and occasionally with Mn minerals. The chlorite/smectite mineral from six gold-silver vein deposits, that is, Konomai, Todoroki, Chitose, Seigoshi, Omidani, and Kushikino was quantitatively analyzed by X-ray microanalyser. The chemical composition of the mineral reflects characteristic features of the ores. Mncontent of the mineral is relatively high and the correlation between Mg and Mn is obvious in the ores containing rhodochrosite, whereas it is very low in the ores free from Mn minerals. Moreover, the Mn/Fe ratio of the mineral varies widely corresponding to the Mn/Fe ratio of coexisting sphalerite. It is infered that the stability and the variations in chemical composition of the regularly interstratified chlorite/smectite mineral appear to be influenced by temperature and chemical composition of ore-forming fluid.