Abstract
The Hitachi ore deposit is generally known as a cupriferous pyrite bedded deposit, and consists of several layers of ore zones, the principal ores being the Hitachi main and the Irishiken ore zones. The former has a trend from NE to SW, while the latter lies paralell, about 1, 000 meters to the North-West of the former. These two ore zones used to be considered separate ones running parallel one with the other.
Since 1953, the writer has come to believe in the existence of a folded structure, after restudying past data. As the result of our recent geological surveys, these two ore zones can now be interpreted as forming a synclinal structure having its apex near the Sasame ore body on the eastern extremity of the main ore body where the folding is prominent.
The distribution of the country rocks and ore bodies are controlled by this synclinal structure, and the trend of the lineations of the rocks are not parallel on the two sides along the axial plane of this folding.
Although follow-up studies are being made, it appears that this structure has an important bearing upon the genesis of the Hitachi ore bodies.
