Geological Structure of the Ehime Mining District, Ehime Prefecture

The Ehime mine is situated about 5., 5km to the south of Niihama., Crystalline schists of the Sambagawa Group outcrop in the district., The crystalline schists of the district are composed of black-schists, originated from argillaceous rocks, sandstone-schists, derived from arenaceous rocks, siliceous schists from quartzose rocks, and green-schists, accompanied by serpentinite., The schistosity planes generally coincide with the original planes of stratification, and they dip mainly to the north., The crystalline schists can be divided litbologically into four formations, as tabulated below in the seemingly descending order., Formation Component rocks S Sandstone-schist and black-schist, interbedded with thin beds of green-schist and siliceous schist., R Black-schist, sandstone-schist, and five beds of conspicuous green-schist with siliceous schist., Q Mainly composed of black-schist., P Thick beds of green-schist, intercalated with thin beds of black-schist and siliceous schist., Structurally, areas may be divided into several blocks, among which the block composed of formation P, and the block formed by formations R and S, are discontinuous., The former belongs to the northern wing of the Sasagamine-Kampuzan anticline, while the latter is the block thrust over the former from the north., Formation Q should be interpreted as the shear zone between these two blocks., The Ehime ore body is deposited in the lowest part of the overthrust mass and is conformable to the foliation planes of the siliceous schist, which extends E-W., Albite porphyroblasts or spots are generally developed in formations R and S, but the spots are not uniform in size throughout the block., The heterogeneous development of spots might have been related to the heterogeneity of the original rock and differences in the amount of deformation., The albitization related to the formation of albite spots was controlled by the modes of deformation and by tectonic transport of the different parts of the deforming block at some stage in the process of the metamorphism of the crystalline schists., Albite spots were enriched in the parts of least componental differential movement., Metasomatizing agents moved through the passage which was formed in the parts of strong componental differential movement.,