24 i'KN'rn F,sKOi,A. N.-N. Kl. 



rock ty|)ii;il (>\ lli<- /gneiss area in Nordfjonl and More. It is a sill-formed 

 mass in iIk qiieiss strikinj^ N 75^ W, in \rrtical position, and was followed 

 about I kilometer alonj^ the strike with a l^readth of about 200 meters. 

 Gneiss bounds it on both sides, and flakes and schliers of gneiss may be 

 seen enclosed in the rock. (3n the northern side, eclogite crops out at 

 many points in contact with the labradorite-rock, and, towards the west, 

 the labradorite-rock strikes in the direction towards the largest mass ol" 

 fili\ine-rock in AlnikIo\dalen (cf. fig. 2). 



The rock is distinctly banded, chiefly owing to an unequal distribution 

 of its dark constituents. Along the strike are arranged many dikes of 

 1 a 1) r a d o r i te-pegm ati te, at times, however, intersecting the banding. 



This lai)i-adorite-rock is mainly composed of 1 a b r ad o r i t e, in sections 

 I PM showing extinction angles of 30 , corresponding to about Ab45 Apjä. 

 A faint zonal structure may be observed. Besides the plagioclase there 

 are small amounts of dark green hornblende, whose amount does not 

 exceed 5 pt ot" the rock mass, and quite trifling amounts of black iron- 

 ore, e p i d o t e and c h 1 o j- i t e. 



The average grain of the labradorite is about 0.6 mm, but there are 

 more fine-grained bands, along the strike. Zoisitization does not occur. 



The structure of the labradoi-ite-rock might be called a p 1 i t i c, all the 

 grains being equally xenomorphic. Protoclastic changes, on the other hand, 

 are apparent. The hornblende, as homogeneous individual prisms, is 

 idiomorphic on the prism zone. There is nothing to point to a secondary 

 origin or uralitic character, and we must conclude that, if pyroxene has 

 ever existed in this rock, it may have been resorbed already during the 

 consolidation and the hornblende crystallized out instead of it. 



Most of the other occurrences show characters strictly similar to the 

 above example, but there may be considerable variation even in a single 

 mass. Thus, of three specimens collected from the occurrence near the 

 Aim klov farm, one has a plagioclase varying from Ab-, to Ab-„^ with 

 at least one third of its mass consisting of intergrown potash leldspar 

 (orthoclase, showing parallel extinction in sections ^ M), and besides much 

 clinozoisite in large crystals bordered by zones of epidote, and biotite, but 

 no hornblende. Another specimen has plagioclase from Ab^^ to Abj^ with 

 much epidote, but no potash feldspar nor dark minerals, while a third, 

 taken from the contact against the gaeiss, has a plagioclase Ab^^ and a 

 pale green hornblende with biotite. 



In a specimen from Skyr fjeldet on San do the plagioclase is 

 anorthitic, varying from Ab32 to Ab^,. The grains have rather rectilinear 

 outlines and the structure is therefore pavement-like. 



In the following list are quoted the compositions of the plagioclase 

 from all the occurrences studied. All the determinations have been made 

 on sections | PM. 



