ON THE SO-CALLED CKYSTALLINE SCHISTS OF CH1CHII3U. Ill 



Granitic eruptions must have taken place through the Archtean 

 group before the Sambagawan was formed ; for, along the c<jast to the 

 north of the city of Imaharu, and especially in tlie upper course of 

 the Nobusigegawa, east of the city of j\Iatsuyama, both in Sikoku, 

 the granitic bosses have severally intruded on tliu mica-schist and 

 gneiss-strata; and have, in consequence thereof, produced a well- 

 marked contact metamorphism in the latter; the deep-brown pyrope 

 having been formed thereby in the hornfeh of the biotite-gneiss. 



Endomorphic metamorphism on the part of the intruding rock 

 is also clearly indicated by the formation of fine-grained, aplitic 

 granophyre-facies of granitite, this being indeed the typical biotite- 

 hornblende variety, of which alone are formed almost all the granitic 



of this Arcbœan belt, an extremely coarse-grained hornblende-granite makes its appearance 

 on the south, convex side, where the granite occupies the greater part of what is called the 

 Tsukude district. This rock shows many characters deviating from the common variety ; 

 first of all it is remarkable in containing a large, grayish-white plagioclase and the cross- 

 shaped twins of hornblende together with biotite and quartz ; the haljitus of the granite is 

 dioritic. In some places, as for instance, at the ascent batween Hosokawa and Suyama, this 

 Tsukude-granite becomes gneissoid in its aspect, due surely to:shearing during the mass- 

 movements. 



Further to the south-east, this eruptive mass is overlaid by the Sambagawan series, the 

 latter is therefore, no doubt, separated from the Archaean by a wide, geologic gap, and along 

 the geologic boundary between the granite and the Sambagawan terranes, the Toyokawa 

 finds its course. The Sambagawan series of this region appears younger in its whole 

 aspect, when compared with the Chichibu type. 



still further to the south-east, this series is overlaid ))y the galjbro-derivatives — tuff- 

 amphiholitc and tuff-pijroxenite with intrusive masses of (jnhhrog and gerpentines, i. e. the Mikabu 

 series of the present writer. Again, the tuff series is covered conformably by the ? pre- 

 Carboniferous complexes of quurtzitc, crystalline limestone, rusty-brown schalstein, grayicacke, 

 adinole, silicious slate and, lastly, a li)nestone presumably the Upper Carboniferous — these 

 together making up the boundary-ridge of Mikawa and Tùtômi. 



It is here out of place to give minute details ; only suffice it to saj' that the writer's view is 

 so far corroborated, that the so-called crystalline schists of Chichibu — the Sambagawan 

 series — are not the oldest geologic body in Japan, and they are also not the normal schists of 

 the accepted Archaean group. Therefore it Avould be a great mistake to make anyc onjecture 

 as to the general construction of the Japanese Islands from the structui-al and the chorie 

 condition of the so-called Archaean group as understood at present by our geologists, since all 

 the non-fossiliferous rocks of quite unlike origin, but having simply a crystalline, schistose 

 habitus are indiscriuiinately thi'own together under the category of crystalline schists in a 

 narrow sense, and taken as the genuine Archaean. (Xotc diirimj the printing j. 



