Photogeology in the Kamaishi Mining Area, Iwate Prefecture, Northeastern Japan

Abstract

Photogeology in Japan has been considered to be very difficult, because, bf small geological units, complicated geological structures, thick surface soil, and artificial forests in the fields. Overcoming these difficulties, however, photogeology has been utilized in the various fields, particularly in the oil fields and limestone areas.
The writers attempted to establish a photogeological standard in the Kamaishi Fe-Cu mining area where Paleozoic sedimentary rocks and Cretaceous igneous rocks (plutonic and hypabyssal) are distributed. They expected to apply it to the exploration of metal mining to get some geological data which was not clear in the previous conventional survey.
From observation of mosaic and stereography of air photographs, using such elements for interpretation as drainage patterns, drainage anomalies, sink holes, mountain ridges, phototonalities, grain textures and fracture patterns, the writers identified igneous rocks and sedimentary rocks, and classified each rock facies as follows:
1) Most of dendritic drainage patterns develop in the area of sedimentary rocks, while parallel or sub-parallel drainages are found in the area of igneous rocks.
2) Drainage anomalies showing anticlines and synclines exist in the areas of sedimentary rocks.
3) Limestones and slates can be identified by the presence of grain texture, phototonality and sink holes.
4) Ganidake granodiorite and porphyrite can be identified by the features of grain texture, photo-tonality and difference of fracture pattern.
5) Tono granodiorite shows typical granitic topography and can be distinguished from other rock facies.
6) In the areas influenced by mineralization, drainage pattern is dendritic, but fracture pattern shows the characteristic of igneous rocks.
7) Anomaly of stream and various kinds of fault topographies were very effective in finding out or in pursuing faults.