The ratios of Cu/Zn-Pb of pyrometasomatic deposits in Japan and their genetical implications

Abstract

The regional characteristics of mineralization in Japanese pyrometasomatic deposits were assessed from amounts of metals, especially Cu, Zn, and Pb, dug out from mines during the past 31 years. For the 49 major mines, the ratios Cu/Zn-Pb and the chemical compositions and textures of genetically related igneous rocks, were determined.Relatively Cu-rich pyrometasomatic deposits tend to be associated with plutonic igneous activity, while Zn-Pb-rich ones are associated with hypabyssal to effusive activity. The relation is clearly demonstrated in the Inner Zone of southwestern Japan. The Cu- and Zn-Pb-rich belts are recognized in the region, and this pattern could be interpreted as the result of a tilted erosion level through an acidic igneous activity of late Cretaceous to early Paleogene.The concept of Cu- and Zn-Pb-rich belts seems to be applicable also to vein-type deposits in the Inner Zone of southwestern Japan. This suggests that the precipitation of base metals in both pyrometasomatic and vein-type deposits may be controlled by the same factor(s), and these factors are not independent of the depth of formation.