Co] p r-Tin Yeirs of tbe Akénobé Districi. 51 



altered to dark green rocks. The gi'een slate is not confined to 

 the walls of the veins but covers a considerable area in this vein 

 district. It is particularly well developed in the Daisen area. 

 When the bedding-plane and slaty structure are indistinct, it is 

 easily mistaken for altered diorite which occurs in large dykes or 

 small bosses here and there in the terrane of the green slate 

 complex. 



Under the microscope, flakes and fibrous flecks of chlorite are 

 abundantly scattered through a clayey ground, sometimes being 

 arranged along the cleavage-plane, intricately mixed with dusty 

 carbonaceous matter. Frequently, the chloritized rock is represented 

 hy sericite-chlorite slate which is made up largely of sericite fibers, 

 minute flakes of chlorite and more or less infiltrated quartz grains 

 — a characteristic hydrothermally altered slate. 



The chloritized slate, as well as the chlorite-sericite slate, is 

 in places irregularly traversed by microscopic quartz veinlets which 

 pass gradually into highly silicified rock-portions (Pi. IL, Fig. 4). 

 It is thus suggested that the main chloritization of the country 

 rock took place prior to the main silicification.i) That the 

 chloritization of the slate is intimately related to the vein-formation 

 is indicated by the fact that the alteration is most intense in the 

 area rich in veins. 



(C) SiLICIFICATION OF THE SLATE. 



The slate adjacent to the veins is often intensely silicified, 

 resulting in a hard quartzose rock usually mottled with light 

 brownish and greenish colours. The silicified slate is commonly 

 cut by netted veinlets of a reddish brown colour. 



1) A s\ibordinate silicification had taken place prior to the main chloritization, the slate 

 being in places altered to an aggregate of fine cuartz grains, which are overlapped by later 

 infiltrated chlorite flakes. 



