r^o Vol. XLIII., Art. 5.— T. Kato : 



economic point of view, the quartz veins of this stage are not 

 important. 



VII. The Alteration of the Clay Slate. 



As already stated, the slate complex, particularly of tho 

 Paleozoic formation, has been subjected to intense alteration. The 

 metamorphism of the complex by dynamic processes has been fully 

 treated under the heading of general geology. In this chapter the 

 alterations obher than dynamo- metamorphism are dealt with, whicli 

 are connected directly or indirectly with the formation of the 

 copper-tin veins of this district. 



(A) DiOPSIDIZATION OF THE SLATE. 



Along some contacts with the dioritic rocks tho slate is 

 metamorphosed into light green rocks, occasionally showing in- 

 tricately contorted, alternating bands consisting of light green 

 compact and deep green granular layers. The deep green gi-anular 

 layer represents an injection of diorito along the bedding-plane, 

 and is composed of crystals and grains of green hornblende with 

 more or less feldspar, while the light green band is composed of 

 silicified slate mingled with abundant patches and streaks consisting 

 of minute short prismatic crystals and grains of colourless diopside. 

 Minute grains of diopside are also scattered through the whole 

 silicified layer (PI. III., Fig. 2). This layer may properly be called 

 a diopside-hornfels, and is one of the typical products of contact- 

 metamorphism. Alteration of this kind is well observed along the 

 road side between Akénobé and the Fiidono pass. 



(B) Chloritization of the slate. 

 The slaty rocks adjacent to the copper-tin veins are usually 



