On the exploration at the Nakatatsu mine, Fukui Prefecture, Japan

Abstract

Pyrometasomatic lead and zinc deposits of the Nakatatsu mine are embedded in skarn zones replacing the Fujikuradani formation of Paleozoic age. Known were Nakayama, Hitokata and Senno deposits occurring from east to west.
Systematic exploration has been carried out in Kurotodo area, the western side of the Nakatatsu mine, on the basis of studies of geological structure, assemblage and distributions of skarn minerals, and characteristics of mineralization. The exploration has resulted in discovery of the Kurotodo ore deposit that consists of numerous massive orebodies in a hedenbergite and garnet skarn zone embedded between limestone and sandstone-slate strata.
Another systematic exploration has been carried out in deeper levels of the Nakayama deposit as well by applying the study of geological structure, skarn mineral zoning and characteristics of mineralization. As the result of exploration, many massive and bedded orebodies have been discovered in hedenbergite and garnet skarn zones, especially in hedenbergite skarn zones, embedded concordantly with general structure of the Paleozoic strata.
A total ore reserve obtained recently at the Kurotodo deposit and deeper levels of the Nakayama deposit has amounted to 1.15 million tonnes (grade Ag 43 g/t, Pb 1.20%, Zn 6.7%) and it contributes greatly to stable operation of the Nakatatsu mine.