1914—15] Fjeld bygningen mellem Sørfjorden og Samnanger: jorden. 235 



The easternmost of the three gneiss-zones consists chietiy of 

 fine-grained grey gneisses. Through inicroscopical investigations it 

 appears that one of the chief types consists chiefly of zirkon, light- 

 brown biotite, felspar, quartz and some calcite. Through an isola- 

 tion of the minerals of the rock the specific gravity of the light- 

 est portion proved to be 2. 61G. It is, however, possible that 

 some grains were not wholly homogeneous, and tims consisted of 

 both orthoclase and plagioclase. The percentage of orthoclase must, 

 however, have been very small, as a chemical analysis only showed 

 very little of K 2 0. The individuals of biotite are strikingly large 

 in proportion to those of quartz and felspar, and have curved lines 

 of limitation, which together with the aspect for the rest, give the 

 impression of a contact melting (Kontacteinschmelzung,GRUBENMANN). 

 The chemical analysis and calculation of it will be seen on pages 

 118 and 120; the structure in fig. 52. 



Edson S. Bastin has found that when in crystalline schists 

 the alloy of Mg is greater than that af Ca 0, and moreover the 

 alloy of K 2 is greater than that of Na 2 0, there is a great prob- 

 ability that the schist is of sedimentary origin. This probability 

 increases still more if the rock contains more Al 2 Oa than can be 

 bound by the alkalis and lime present. 



The very contrary is the case with the analysed gneiss from 

 Aldal, which, therefore, is likely to have been of eruptive origin. 

 It has then been either a volcanic rock or an injection-mass, which 

 has been pressed in a direction nearly parallel to the stratification. 



The possibility of its being an eruptive rock older than the 

 phyllites, which has been pressed in between them during the great 

 folding of the mountain-chain, is not great. 



Similar gneiss-rocks occur in the eastern part of the Samn- 

 anger-area, which, as may be seen in the photograph, fig. 54, from 

 the west side of the road between Tveit and Fiske, distinctly 

 overlie the phyllites, which have a dip of 45° towards east. 



The Gneiss-Rock of the Peninsula of Haukenes. 



(Pages 121—128.) 



The peninsula in the inner part of Aadlandsfjorden, and 

 whereon is situated the farm of Haukenes, consists of gneissose 

 rocks, the continuation of which Ave tind on the south side of 



