相内鉱山,大黒鉱床における級化鉱石の産状

その鉱床学的,探鉱上の意義にいつて

抄録

The Daikoku deposit of the Ainai mine belongs to "Kuroko"-type deposit, having zones of siliceous ore, gypsum, and stratified ores.
In this deposit, stratified sulfide ores are grouped into two types, depending on their modes of occurences.
In the southern part, the ore bodies consist of, in the ascending order, siliceous ore, stratified yellow ore and black ore. These stratified sulfide ores are very compact, and have banded texture of pyrite and chalcopyrite in some cases.
On the other hand, in the northern part of the deposit, the bedded sulfide ores contain fragments of compact black ore and yellow ore in the matrix consisting of cubic pyrite, crystal barite and clay material. And the ores can be classified into two types ; namely, the "massive part" with coarse grained and unsorted ore fragments, and the "bedded part" with fine grained and bedded material.
In the latter case, several units of vertical sorting of ore fragments and pyrite crystals are observed. In each unit, grain size of ore fragments and cubic pyrite decreases from the lower horizon to the upper horizon. In the upper part clay minerals are predominant. Also, "sole mark" and "imbrication" structure, which are very common in pyroclastic flow sediments with submarine turbidity currents, are found in many places of the ore deposit.
It is suggested for the evidences mentioned above that the graded ores in the northern part of the Daikoku deposit were settled secondarily by the submarine currents from the original ore bodies deposited primarily at sea bottom.
Thus, it is expected that black ores may be found in the northeastern extention of the Daikoku deposit judging from the analysis of geologic structures and "the study of sorting of ores.