Some Problems Concerning the Hitachi Pyritic Deposits

Abstract

The geology of the Hitachi mining area is highly complicated by the original difference of rock facies, combined with various degrees of dynamic, contact and hydrothermal metamorphism. The deposits are developed along some sheared zones, especially located at some blind spots of stress. The ore might have been transported to such places by solutions, derived at much deeper zones of an orogenic belt, not. necessarily by magmatic intrusion, but perhaps by selective extraction of rock materials by superheated vapour there originated by dissociation of hydrous minerals. This supposed process is called “abyssal secretion”. Extraction of materials from strongly stressed country rocks and their deposition at local non-stressed points may be also possible-to some degrees. The term “lateral secretion” may be used also in sucha sense. Some deposits in this area, characteristic off high, temperature origin, may be those farther metamorphosed by later intrusion of granodiorite.