1979 Volume 29 Issue 155 Pages 161-174
The Nippo ore deposit, formerly called the Ohmine deposit, is a pyrometasomatic copper deposit. Recently the mining development has been carried out in the lower level of the deposit and some interesting geological phenomena different from those observed in the upper level have been encountered.
Skarns and mineralized rocks are classified into six types: banded skarn, diopside skarn, garnet skarn, hedenbergite skarn, brittle skarn (so-called "bosa" garnet skarn), and quartz vein. Of these rocks, diopside skarn, garnet skarn, hedenbergite skarn, and quartz vein are accompanied by ore minerals. Two types of zonal arrangement of skarns are observed: (1) hornfels through banded skarn, diopside skarn, garnet skarn, hedenbergite skarn to limestone, and (2) quartz diorite through garnet skarn, hedenbergite skarn to limestone. The former is seen between slate and limestone and the latter between quartz diorite and limestone. Assemblages of ore minerals are chalcopyrite-cubanite-pyrrhotite, chalcopyrite alone, chalcopyrite-bornite, chalcopyrite-pyrite, and chalco-pyrite-pyrrhotite.
The orebodies of this deposit are classified into two groups: one is associated with diopside skarn and garnet skarn, and the other with hedenbergite skarn and garnet skarn. The former type of orebodies is massive in shape and the latter is tabular and commonly accompanied by vertical quartz veins. The mineralization of these orebodies seems to be strongly controlled by the pre-ore faults.
