Abstract
The middle region in the field is numerous faults of NWSE trend associated with dip faults, diagonal faults and strike faults. Therefore, as a result, the Yoshino formation, Kaminoyama shale and mudstone member and the Motozawa formations have their relations served.
It is within this region that block tilting occurs, and the whole represents a mosaic structure highly disturbed. It is in this structurally complicated region where the metal ore deposits are concentrated.
The structurally disturbed area which measures 7 kilometers in breadth and trends in NW-SE direction for a distance extending far beyong the area surveyed by the writer, is here named the Yoshino structural zone.
It is to be stated that all of the ore deposits appear to be concentrated to the Yoshino structural zone and comprise types referable to vein-, etwork-, and replacement deposits. These ore deposits are governed by the particular structure in the Yoshino structural zone and by physicochemical phenomena, and are concentrated in the regions of faults which served as routes for the upward flow of the mineral solutions resulting chiefly in deposition, of the ores. It is of interest to find that the arrangement of either of minor fault or of tension- or gash fracture in a definite direction results in the deposition of vein ores. When the arrangement of the aforsaid structure cross one another, network deposits are developed. In cases where cap rocks occur in the latter mentioned kind of structure, replacement deposits develop. Field observations reveal that the ore deposits are not selective as to their mother rock or stratigraphic horizons within the Yoshino structural zone.
