1985 Volume 35 Issue 190 Pages 133-144
The Kamaishi mine, located in northeastern Japan, is typical of skarn type copper-iron deposits. The Shinyama ore deposit, the largest one in the mine, consists of thirteen copper, copper-iron and iron orebodies. These are embedded in the skarn zones distributed along the rim of limestone of Carboniferous age and in diorite porphyrite belonging to the Ganidake igneous complex of early Cretaceous intrusion.
The recent exploration have been performed to discover high grade copper ores. The ore reserves confirmed between 1979 and 1984 were about 1.2 million tons. Especially we discovered the New No. 5 copper orebod, by tracing along the thrust fault separating the No. 2 and No. 3 limestones.
Its geological characteristics are as follows.
(1) The skarn is characterized by clinopyronexe, clinopyroxene-epidote, and epidote-garnet from limestone to diorite porphyry or slate. The copper mineralization is restricted within the clinopyroxene zone.
(2) It is divided into five unit orebodies called as V1, V2, V3, V4, and V5.
(3) The V1, V2 and V3 in the form of ore shoot are emplaced on the crest and east frank of the No. 3 limestone.
(4) The V4 and V5 extend toward north to south on the west frank of the No. 2 limestone.
(5) The former three resulted from the ore solution ascended along small geological structures bevelling the thrust fault, the latter two along it.
Further high grade ores are found around the New No.5 copper orebody by tracing and re-investigating the morphology of the limestone, diorite porphyrite and skarn as well as ores.
