28 Carl Fred. Kolderup. [Nr. lft 



kollen is about 40 km. The dyke that is cutting" the E.— W. 

 striking metamorphosed silurian stratas near the little lake Strynvand,, 

 was found by Hiortdahl and Irgens 1863. Seeing that the 

 rock was very similar to the rocks from Sogneskollen, I studied it 

 in connexion with these. The result of the chemical analysis can 

 be seen page 10. The mineralogical composition is about 55 2 /3 % 

 plagioclase, 12 % orthoclase and microcline, 23 % quartz, 9 % 

 muscovite and epidote and l U % zircon, apatite and titanite. 

 Also in this rock the plagioclase is the predominating mineral; it 

 belongs to the albite and the oligoclase-albite series. The structure 

 is a protoclase structure. 



The Granodiorite („ White Granite") of Bremangerland. 



Bremangerland is a large island situated at the mouth of Nord- 

 fjord in Western Norway, about 35 km. north of the above mentioned 

 island of Svanø. The granodiorite occurs on the southern coast and on 

 the adjacent smaller islands as seen on the map (Fig. 4). The area has 

 earlier been studied by the Norwegian geologists Hiortdahl and 

 Irgens (Om de geologiske forhold paa kyststrækningen af Nordre 

 Bergenhus amt. Kristiania 1864) and Reusch (Konglomerat og 

 sand stensf elterne i Nordfjord, Søndfjord og Sogn. Nyt Mag. f. 

 Natv. B. 26). Tn order to know the chemical composition of the 

 rock I had the chemist Landmark at Bergen to make an analysis 

 of one of the most typical varieties, the result of which is published 

 page 13. The white granodiorite contains the following minerals: pla- 

 gioclase, mikroperthite, perhaps also in some varieties small quantities 

 of orthoclase, quartz, biotite, epidote and zoisite, muscovite and 

 sericite, garnet (only fe w crystals in one type from the neighbour^ 

 hood of the border), magnetite, zircon, apatite and titanite. The com- 

 position of the analysed type is about 62 % feldspar, 27 3 /4 % quartz, 

 9 % biotite, 2 /s % magnetite and Vs % pyrite. The microscopical 

 investigation and the isolations show that there is no orthoclase or 

 microcline in the rock; the plagioclases must therefore contain some 

 K 2 0. They are andesine, oligoclase and albite. The structure is 

 generally granular, but very often also a parallel texture is well 

 developed. By microscopical investigations we find a cataclastic 

 texture especially in the neighbourhood of the border. At the. 

 borders the granite often becomes fine-grained and the adjacent 

 schists show some metamorphism, and in several places dykes of 



