The Kuroko and related volcanogenic massive sulfide deposits

摘要: This paper consists of three parts. The first is an overview the geologic history Green Tuff region where all Kuroko deposits occur. second part presents a description stratigraphy and interpretation structural igneous Hokuroku district, most important mining district. third analysis role submarine calderas in genesis. The sequence causes major events that have occurred Japan its vicinity since Cretaceous are interpreted as follows: (1) active but shallow-dipping north-northwestward subduction Pacific plate under Asian continent during period from approximately 130 to 65 m.y. ago resulted ilmenite series magmatism outer zone Japan, then still mainland Asia; (2) about 40 ago, direction subducted changed westward angle steepened, initiating back-arc spreading basin province migration away until 30 ago; (3) basaltic crust created was eastward Yamato Ridge province, resulting calc-alkaline magnetite activity inner Japan; (4) 25 sea (proto-Japan Sea) formed result eustatic rise following cessation there (5) between 5 cansing bimodal volcanism subsidence flanking Inner Honshu provinces [the (i.e., Kuroko-bearing basin), Niigata oil field basin, Akita were fault-bounded, deep (>2,500 m) marine basins by rapid crustal blocks within few million years around 17 although mineralization accumulation organic matter not synchronous]; (6) dip returned shallow causing initiation uplift provinces. is, therefore, synonymous with tectonic accompanied formation Sea Japanese islands ~65 present.