Iwaaaki 



4. Metallogenetic Provinces. 



In Japan, there are several kinds of ore-briiigers, such as granite^ 

 diorite-porphyrite, liparite, and andésite ; serpentine is also suppos- 

 ed sometimes to have a genetic relation to ore-deposits. All these 

 rocks occupy their own areas, which we call here metallogenetic- 

 provinces, after A. M. Finlaysox,^^ who made similar divisions of 

 the British Isles. Granite is very extensivel}' exposed in Japan, 

 but it is not always associated with ore-deposits. As an ore-bringer 

 it is most frequent in Korea, and also in many places in northern 

 Kyûsliû as well as in western Honshu (the Main Island). Quartz- 

 porphyry associated with ore -deposits in central Japan is also 

 asserted to be the marginal facies of this particular province includ- 

 ing Korea and other regions. Tliese localities therefore may be- 

 called the Korean Province. 



Diorite is not scanty in Japan, and a noteworthy fact is that 

 diorite-porphyrite is rather better suited to be an ore-bringer tlian 

 diorite proper. The ore-deposits formed by emanations from 

 diorite-porphyrite are chiefly found in the Paleozoic formation in 

 the outer zone of North Japan, with their center in the Kitahami 

 Mountain-land, which, possessing most numerous deposits of this 

 sort, may give the name to this Province. Liparite lava is not 

 very often met with in this country, but the rock doing the function 

 of an ore-bringer is found more frequently in the form of dykes or 

 necks, nearly always in the inner zones of North and South Japan, 

 which are put together under the name of the Kosaha Province, 

 the Kosaka Mine being its exponent. Besides liparite, propylite- 

 is somiCtimes found doing the work of an ore-bringer in this 

 province. Andésite is the volcanic rock of widest occurrence in 

 Japan, but it is not always associated with ore-deposits. The rock 

 which serves as an ore-bringer is rather the older rock of this kind, 

 recent andésite lava being always barren of the useful heavy 

 metals. The greater part of the andésite that acts as an ore- 

 bringer is supposed to have erupted in the later period of the 

 Tertiary and the earlier portion of the Diluvial, and intrudes 

 Tertiary sediments, forming dykes, necks, or denuded volcanoes. 



1) Finlayson : Quart. Jour. Geol. Soc. London, p. 281, 1910. 



