The writer surveys the Doshinkubo ore deposits of the Chichibu mine, which belongs to the magnetite deposits of the pyrometasomatic type consisting of pyrite, pyrrhotite, chalcopyrite, and some silicate skarn minerals. At the contact between the quartz-diorite and limestone, the following zones of mineral association were recognized by megascopic and microscopic observations.
Zone 1: quartz-diorite, which is composed of quartz, plagioclase (An₄₅ Ab₅₅_??_An₅₅ Ab₄₅), brown hornblende, biotite and blue actinolite.
Zone 2: mixed rock zone (width; 20_??_30cm.), which is composed of quartz, plagioclase, brown hornblende, diopside, garnet, chlorite, and calcite.
Zone 3: vesuvianite-xanthophyllite zone (width; about 2m), which is composed of vesuvianite, diopside, wollastonite, garnet, and xanthophyllite.
Zone 4: garnet-chlorite-epidote zone (width; about 10m.), which is composed of andradite, pistacite, and chlorite.
Zone 5: magnetite ore body (width; about 30m.).
Zone 6: hedenbergite-ilvite zone (width; about lm.).
Zone 7: limestome.
The occurrence of the Zones 2 and 3 are closely related, with an intrusive body of the quartz diorite, and those of the Zones 4, 5, and 6 controlled by the formation of the ore body. From the observation mentioned above, the writer suggests that the Zones 2 and 3 were formed by the magmatic “reaction” between the quartz-diorite magma and limestone, but the Zones 4, 5, and 6 may be the products of the mineralization at the later stage.