JOUIiNAL OF THE COLLEGE OF SCIENCK, TOKYO IMPERIAL UNIVERSITY. 



VOL. XXXII., ARTICLE 8. 



The Metallogeny of the Japanese Islands. 



By 

 C. Iwasaki, niqahushi. 



With 1 Map. 



1. Magmalic Emanations and their Petrification. 



Since SvanteArrhenius^^ made public the results of his studies 

 on the chemical properties of water in high temperatures, the 

 world's geologists have been more or less influenced by him, their 

 views on metallogeny changing gradually from the hydrothermal 

 to the magmatic theory, Heavj" metals were formerly supposed 

 to have been brought up by hot springs in the form of mineral 

 solution. But at present ore-deposits are believed to have been 

 deposited by gas, or by a mixture of gas and liquid, or by liquid 

 only, emitted from magma while cooling. This is asserted by 

 J. H. L. VoGT,'^ who calls this ''eruptive after-action." This view 

 naturally leads us to believe that where ore-deposits exist, there 

 must be found igneous rocks, near or distant, from which the 

 materials of the ore-deposits were emitted. Prof. Koto,^^ in 

 his recent paper entitled " Geology anà Ore-deposits of the Holgol 

 Mine,'' 1910, calls these rocks '' ore-bringers." 



It had already been recognized by Matteucci, Lacroix,*^ 

 Gautier,^ and others that a great many elements always exist in 

 emanations. When the latter cool, these elements form different 

 kinds of minerals. It is in this way that petrification of emanations 

 takes place. 



1) Svante Arrhenius : " Zur Physik des Vulkanisms," Stockliolm, 1900. 



2) The Genesis of Ore Deposits," p. 642. 



3) B. Koto : Jour. Coll. Sei. Imp. Univ. Tokyo, Vol. XXVII., Art. 12, 1910. 



4) Matteucci and Lacroix: The Digest in Economic Geolor.u, Vol Tl., No. 3, p. 25S, 1907. 



5) Gautier : Economic Geolomj, Vol. I., p. 690, 1906. 



