THE ARCH^AN FORMATION OF THE ABUKUMA PLATEAU. 21^ 



piedmontite/ which is of very wide distribution elsewhere in Japan, 

 especially in the island of Shikokii. The chlorite schists are followed 

 by another bind of platy epidote-amphibole slate (a), which is tilted up 

 in vertical position like the overlying- rocks, and is partly corrucrated 

 at its junction with the biotite-granite (1) (1), indicating that the latter 

 has broken through the former, and brought it to its present form. 



Beyond the small ridge of Komori-zuka" (574 m.), the horn- 

 blende-granite makes its appearance, often interrupted by a later 

 eruption of the bifjtite-granite, and nlso by the formation of aplitic 

 dykes (d). Between Jùmoji and Kodaira, we meet with a detached 

 mass of the titanite-amphibolite (U T A) of tolerably large dimen- 

 sions. This soon gives way to the hornblende-granite, which is more 

 or less gneissose (G H 11), with the plane of schistosity inclining towards 

 the east, having just the same dip as the last-mentioned patches of 

 amphibole schist. At Xakagura the granite has acquired a peculiar 

 hal^itus (Xakagura type), owing to the predominance of somewhat 

 large grains of quartz, which gives to the rock a blotchy appeaî'ance. 

 Farther to the west the line of contact of the granite with schists is 

 observed, in which the irruptive nature of the former through schists 

 is clearly marked. Not far from the line of contact, a dyke (L P) of 

 about 2 m. thickness is found in a vertical cleft. The material of the 

 dyke is of a dark-greyish colour with brown spots. Microscopic 

 analysis, the details of which are given in a separate section, proves it 

 to be an augite-dioritic lamprophyre. 



From Xakagura to »Söri, through Otsuka and Nakata, the rocks 

 exposed are multifarious alternations of thin bands of titanite-amphi- 

 bole schists, and gneiss-mica schists (U T A). Of the amphibole 



1 This journal, Some Occurroia'^: of Piedmontite in Jdpan, Vol. I. p. 303; also On the so-call- 

 ed Crystalline Schists in Chichibu, Vol. II. p. 93. 



2 See the line of section E-F, PI. XXV. 



