T92I. No. 8. 



ox THK ECLOGITES OF NORWAY 



mylonitic gneisses. Such augengneisses showing marked granitoid structure 

 ha\e, in Norwegian literature, been called gneiss-granite. 



We shall at first gi\-e a few examples of the petrographical characters 

 of the gneisses. 



Gneis s-g r a n i t e f r o m the island Silden, S e 1 j e. A porphyritic 

 granite whose phenocrysts, two or three centimeters long, are somewhat 

 drawn out into lenticular eves. Thev consist of crosshatched microcline 



60 W. of Christiania 5O 4O 3O 



Fig. 2. Map of parts of Xordfjord and More. White = gneiss; black = olivinc-rock; dotted 

 = eclogite; shaded = labradorite-rock ; crosses = limestone. 



containing much oligoclase as perthitic threads. The ground-mass, fine 

 in grain and with serrated boundaries between the constituents, is composed 

 of microcline, oligoclase, quartz, bi otite, epidote and z o is i te, 

 and chlorite. The oligoclase, in sections J_ M, shows extinction almost 

 parallel to the trace of M. The biotite, dark brown in colour, occurs as 

 groups of parallel fine scales among which also occur grains of zoisite 

 with border zones of epidote. The refractive indices of the components 

 of this homoaxial intergrowth show the following relation: y epidote ^> y 

 zoisite and a epidote <C y- zoisite. 



Augengneiss from Vederhus, S el je. This rock is megascop- 

 ically a gneiss-granite, but its phenocrysts have in part been granulated 

 into a very fine mass of microcline. The ground-mass also is fine, 



