Epithermal vein-type mineralization in a compressive stress field, southwest Hokkaido, Japan
published: Nov 27, 1995
ArtNo. ESP136000501004, Price: 19.00 €
Late Cenozoic epithermal deposits in southwest Hokkaido, Japan, consist largely of vein-type, stratabound and Kurokotypes. The vein-type deposits formed in compressive settings at 12-10 Ma and 6-0 Ma. The maximum principal stresses derived from conjugate sets of veins of the Pliocene and Quaternary trend N50°W at the Jokoku deposit, N75°W at the Toyoha, Chitose and Inakuraishi deposits and E-W at the Yakumo deposit. These trends, except for that at Yakumo, are compatible with the regional stress field deduced from dike trends in the area. The fracturing of the Yakumo deposit is attributed to E-W shortening movement during the Pliocene and Quaternary in the southern part of southwest Hokkaido. The dextral strike-slip and shortening movements in southwest Hokkaido are reflected by dextral strike-slip and conjugate vein patterns. These movements appear to have been activated and the majority of the vein-type deposits formed, over the period about 3.5-1.5 Ma. A rapid rotation of the maximum principal stress from N70°W to N30-40°W at about 1.25 Ma possibly changed the pathway and direction of the flow of ore-solution in the Toyoha deposit; this was also associated with a change in mineralization style, from Pb-Zn to polymetallic. Thus, the epithermal vein-type mineralization in southwest Hokkaido has been strongly influenced by the magnitude and orientation of the compressive stress field, related to subduction of the Pacific plate.