Manganese, Lead, Zinc and Silver Mineralization at the Matahachi Deposit of Jokoku Mine, Southwestern Hokkaido, Japan

Abstract

Neogene mineralization related to the formation of magnetite skarns and manganese, lead, zinc and silver veins at the Matahachi deposit in the Jokoku-Katsuraoka mining area is summarized on the basis of macrostructures and mineral paragenesis of individual ore bodies, mineralization stages, hypogene zoning and environment of ore formation. The mineralization sequence, from earlier to later, is divided into five stages as follows; Stage I: formation of magnetite skarns, Stage II: formation of Pb-Zn-(Cu) quartz veins, Stage III: formation of Pb-Zn-(Mn) quartz veins, Stage IV: formation of (Pb)-(Zn) rhodochrosite veins, rhodochrosite veins and massive rhodochrosite deposits and Stage V: formation of ferromanganoan dolomite veins. Mineralization of stages (I) through (V) at the Matahachi deposit is closely related to the mineralization events showing polyascendent zoning. Three major kinds of vein deposits at the Matahachi deposit include Pb-Zn-(Mn) quartz veins, well-crusted banding (Pb)-(Zn) rhodochrosite veins and rhodochrosite veins. Ore types such as Pb-Zn, well-crusted banded rhodochrosite and rhodochrosite ores are correlated with ore grade. Based on ore grade, the three zones are arranged from the northwestern to southeastern part of the deposit in the order of Pb-Zn, Intermediate and Rhodochrosite zones. Pb-Zn-(Mn) quartz veins tend to occur in the Pb-Zn zone of the deposit, while rhodochrosite veins are widely distributed in the Rhodochrosite zone. Horizontal and vertical zoning could be formed by polyascendent mineralization related to formation of Pb-Zn-(Mn) quartz, (Pb)-(Zn) rhodochrosite and rhodochrosite veins. Formation temperatures gradually decrease from earlier to later stages at the Matahachi deposit. Changes of formation temperatures correspond to the progress of mineralization stages associated with multiple mineralization.