PRELIMINARY NOTES ON SOME IGNEOUS ROCKS OF 



JAPAN. IIP 



S. KOZU 

 Imperial Geological Survey of Japan 



III. ALKALI-FELDSPAR-BEARING BASALTIC ROCK (fUKAE-GAN) AND 

 ALKALI-FELDSPAR-BEARING BASALT 



Localities. — Alkali-feldspar-bearing basaltic rocks were collected 

 from Fukae-shima in the Goto Islands; alkali-feldspar-bearing 

 basalts from Madara-shima, an islet northwest of the Yobuko 

 port, prov. Hizen; from O-shima, near the Island of Iki; from 

 Uramino-taki, near Omura city, prov. Hizen. These localities are 

 in the northern part of Kyushu or its outlying islands. 



Occurrence. — The rock type, associated with olivine-basalt on 

 the one hand and with soda-trachyte 2 on the other, appears to 

 have an extended distribution over the northern part of Kyushu. 

 At Fukae-shima, this rock group forms the plateau and some 

 striking dome-shaped hills standing on it, as seen in the photo- 

 graphs (Figs, i and 2). There are well preserved or strongly 

 breached craters in the summit of each dome. The hills, in great 

 part, consist of ashes, lapilli, and slaggy lava, in which finely 

 shaped bombs may be found abundantly. The plateau is of hard 

 lava. 



Age.— Near the close of Tertiary to Diluvium. 



The specimens for the following descriptions were collected by 

 the writer from Fukae-shima; by Y. Otsuki from Madara-shima 

 and O-shima; and by D. Sato from Uramino-taki. They may be 

 classified in two groups by the mineralogical and chemical char- 

 acters. 



I. Alkali-feldspar-bearing basaltic rock (Fukae-gan in Japanese) . — 



The rocks of this group collected from Fukae-shima are transi- 



1 Published by permission of the Director of the Imperial Geological Survey of 

 Japan. 



2 Jour. Geol., XIX (191 1). 



566 



