1989 Volume 39 Issue 216 Pages 273-281
Survey on the relationship between the geologic structure and the ore vein patterns in Sapporp-Akaigawa district, southwestern Hokkaido, leads to the following conclusions.
(1) The Todoroki, Nakanosawa and Higashi-Kucchan vein systems were formed by the sinistral shear of E-W trend under the weak compressional stress field with maximum compressional stress axis of ENE-WSW direction at the latest Middle Miocene.
(2) The Toyohiro, Otoyo and Shin-Otoyo vein systems were formed under the tensional stress of ENE-WSW trend at the earliest Late Miocene.
(3) The Toyoha veins have been formed by the dextral shear with normal fault sense of E-W trend under the medium to weak tensional stress field of which maximum horizontal compressional stress axis has been WNW-ESE to NW-SE trend since the Late Miocene.
(4) The fracturing and the mineralization of the veins started simultaneously under control of the structural movement and the regional stress field for each of these deposits.
