足尾鉱山の累帯構造

抄録

The Ashio Mine is composed mainly of the rhyolitic comlex and the Palaeozoic formation. The ore deposits occur both in them as vein and "Kajika" deposits.
Four hypogene mineral zones, a central Sn-W-Bi-Cu zone, an intermediate Cu-As-Zn zone, a marginal Zn-Pb-Cu-As zone and a barren zone are quite distinguished in the rhyolitic complex as Takeshi NAKAMURA (1961) clarified them.
Hypogene mineralization in the Palaeozoic formation and in the southern part of the rhyolitic complex adjacent to the Palaeozoic formation is very similar to that in the rhyolitic complex, but large amounts of ealier pyrrhotite and marmatite occur in the Palaeozoic formation. In general, three mineral zones, a Fe-Zn-As zone, a Cu zone and a silicified and barren zone are distinguished remarkably from the foot-wall side to the hanging-wall side of the "Kajika" deposits in the Palaeozoics.
The mineralizations both in the rhyolitic complex and the Palaeozoics are considered to be taken place at the same time after the rhyolitic complex extruded.
The features of the high-temperature tin and tungsten minerals are associated with the low-temperature copper, lead, zinc and other minerals show the telescoped character of the Ashio deposits. The ore deposits at the Ashio Mine classified as the epithermal deposit are considered to be formed under the subvolcanic environment caused by the vocanism of the Ashio rhyolitic complex.