Recent Exploration of the Fukazawa Kuroko Deposits

Abstract

The Fukazawa kuroko deposits were discovered in the nearly central part of the socalled Hokuroku basin, northern Akita Prefecture, by drillings in 1969. The deposits consist of three main ore bodies and several small ones.
The following geological characteristics were revealed as a result of the development of the Tsunokakezawa ore body, one of the major ore bodies.
(1) The Tsunokakezawa ore body is a typical stratiform type kuroko deposit having lateral continuity. The ore body hardly shows any post-ore deformation.
(2) The ore body shows a vertical zonal arrangement, silicified rock, siliceous ore, gypsum ore, yellow ore, black ore, barite ore and ferruginous chert zone in ascending order.
(3) There are some isolated siliceous ore bodies accompanied by the yellow ore and the mineralized hanging wall basalt nearby.
(4) The nature of mineralization of the siliceous ore bodies alters gradually simple veins, network veins, network veins-impregnation and stratiform ores from bottom to top.
(5) The stratiform ore body is concordant with the thin bedded fine tuff of the hanging wall and the black mudstone of the footwall.
(6) In some places reworked sedimentary textures of the ores are found especially near the upper portion and marginal part of the ore body.