Geology and Ore Deposits of the Shakanai Mina(3).On the Mode of Occurrence and Texture of Yellow Ore in the No.4 and No.8 Ore Deposits.

Abstract

The major part of the No.4 and No.8 ore deposits is a stratiform yellow ore body with an overlying layer of black ore and an underlying gypsiferous bed. The yellow ore body in many places can be divided in four unit zones, zone I, IIA, IIB and IIC in ascending order, according to the structure and texture of ores. Thin layers of argillized tuff occur in between and within different yellow ore zones as intercalations.
The major sulphide mineral of the yellow ore zone I is pyrite with very small amount of other sulphides, and the ore shows subangular to subrounded fragmental structure in a argillized and pyritized tuff. In the yellow ore zone II A and II B, chalcopyrite increases successively and fills interstices and matrix of pyrite grains. Ore minerals of the zone II C are a large amount of chalcopyrite and a less amount of pyrite, sometimes with fragments of black ore.
Graded bedding of lithic and ore fragments is observed clearly in zone I but also noticeable in zones II A and II B, while structures of slumping and imbrication of ore blocks are especially observed in the zone II C. Thus, the yellow ore zones indicate also such sedimentological features as those often observed in the black ore zone. So far as the ore deposits under consideration are concerned, they may have been formed on the sea floor under the influence of turbidity currents.