66 ALASKA GEOLOGY 



about eight feet thick and parallel to the structure of the 

 schist. The aplite has an indistinct schistosity parallel to 

 its walls, and shows many films of sericite, doubtless 

 formed during the shearing to which it has been subjected. 

 The quartz and feldspar of which it is composed, partly 

 in indistinct phenocrysts, show strain effects but little al- 

 teration in the thin section (NO. 27). 



This series of greenstone schists, some of which at 

 least are clearly derived from igneous rocks, is additional 

 evidence of the correctness of Dawson's correlation of 

 the black slate or argillite of Juneau with his Triassic 

 Vancouver Series, which in the type locality also contains 

 large bodies of metamorphic eruptives. 



