284 



B. KOÏO. 



IX. Summary. 



The Dfeneral results I have arrived at by mv atudv of tlie 

 archgean formation of the Aljukuma plateau may be summarized 

 as follows : — 



This archeean plateau constitutes a portion of the ecto- peripheral 

 zone of the ISTorth Japan garland,^ jmd is separated from the ])aekbone 

 of the island by the longitudinal valleys of the Abukuma-gawa and 

 Kuji-gawa, while on the east it is bordered by the Pacific sea-board. 

 The south end of this arcluean zone has been the subject of one ' of 

 my former papers. The present one is the result of study made in 

 the northern prolongation of the same belt, i.e., the Abukuma plateau. 



The archcTean rocks of this region are ]jrimarily separable into a 

 lower division, the Laurentian, and an u})per division which again 

 may be subdivided into two well-recognizable, leading groups, the 

 Gozaisho and the Takaniiki series. 



The Lawoition is mainly composed of rocks of the grariitic, 

 syenitic, and dioritic types of mineral ogical composition, and panidio- 

 morphic-hypidi(jmorphic granular structure. These granitic-granular 

 rocks show in places different degrees of schistosity, depending u])on 

 the circumstances under which they have been formed. Accordingly 

 we have a number of foliated granites which may be conveniently 

 brouo-ht tofj-ether under the followinn: head;?, viz., 1) imiierfectly schis- 

 tose amphibole -granite, 2) schistose amphibole-granite, and, lastly, 3) 

 schistose epidote-granite. The young biotite-granite, though less ex- 

 tensively developed than the other, has also equi^•alent modifications. 



1 The late Melchior Neiimayr, when speaking of volcanic islands, said: Vom Feuerland an 

 zieht nich eine Riesenkette gewaltiger Vulkane nach Norden, his Alaska, wo dann jene eigentümliche 

 Bildung geschtcun gener Vulkanreihen, meist auf Inseln gelegen, beginnt, welche (Festoninseln) man mit 

 herabhängenden Blnmengewinden verglichen hat. Erdgeschichte, I Band. 



2 See p. 198. 



