The Fujigatani Mine is one of the important scheelite-ore deposits of contact metasomatic origin, and is located in the Kuga district, Yamaguchi Prefecture.
The Palaeozoic formation consists of slate, chert, sandstone and lenticular limestone, and is intruded by dikes of aplite, liparite and lamprophyre. In the southern region of the district, biotite granite crops out and argillaceous sediments are converted to spotted slate or biotite hornfels as a result of this batholitic intrusion.
The ore deposits can be classified into the following two types:
1) Contact-metasomatic massive ore deposits
2) Scheelite-quartz vein ore deposits
The main ore deposit consists of four groups, and many ore bodies in each group are arranged parallel to the fold axis. As the form of the ore bodies is clearly controlled by geologic structure, the slip plane (S) and lineation (L) of the country rocks or limestone bodies, the direction of the ore shoots and variation in thickness of the ore bodies can be determined geologically.
The writer analyzed them by the "L-S Fabric Analysis" method presented by R. Sugiyama to analyze the fabric inwoven by lineation and the schistosity plane of the rocks. The chief constituents of the contact-metasomatic ore are scheelite, associated with chalcopyrite, pyrrhotite and other sulphide minerals. The skarn minerals are garnet, diopside, hedenbergite and quartz.
Scheelite-quartz veins are observed in joints or minor slip planes, and are younger than the contact-metasomatic deposits.
The tungsten content is especially high where these scheelite-quartz veins cut the skarn mass. Joints or minor slip planes are considered to be tension cracks normal to the fold axis of the area.