Vol.50.] BASIC EEUPTIVE ROCKS OF GRAtf. 1 '.) 



In the northernmost locality, Brandberget, the prevailing rock is 

 a very basic olivine-gabbro-diabascs, so poor in felspar that it passes 

 into pyroxenite. Jointly with this predominant rock there occur 

 also, to a great extent, typical pyroxenites, often of very coat-' 

 grain, besides coarsely radiated hornblendite (with the hornblende- 

 prisms measuring as much as 10 centimetres or 4 inches in length), 

 the latter rather subordinate, and also subordinated hornblende- 

 bearing gabbro-proterobases and other rocks with brown basaltic 

 hornblende. These basic rocks (the pyroxenite, the hornblendite, 

 and the gabbro-proterobase) are traversed by innumerable segrega- 

 tion-veins of a fine-grained augite-diorite or augite-syenitc (akerite), 

 which will be further referred to a little later on. 



Moreover, in the small exposures of Augedal, Solberg, and Bilden, 

 very basic varieties — pyroxenites combined with camptonites — 

 prevail. 



On the top of Solvsberget a more acid olivine-gabbro-diabase is 

 already the prevalent rock ; pyroxenites and other basic rocks are 

 there only observed as rather subordinate contact-facies. 



We find the same conditions in the Yiksfjeldene, where also more 

 acid segregation-veins of augite-diorite, etc., are widely spread. 



The most acid rock is represented in the occurrence at Dignaes ; 

 the ultrabasic types are entirely wanting here, the predominant 

 rock being an olivine-gabbro-diabase rich in felspar. 



The following analyses (Table I.) serve to illustrate the successive 

 changes in the chemical composition of the prevalent kinds of rock 

 from north to south : — 



Table I. 



I. II. III. 



Si0 2 4365 4700 4925 



TiO; 400 230 141 



Al o 3 11-48 15-20 1697 



Fe"0" 632 569 



FeO." 800 6-59/ 



MnO Trace 026 Trace 



MgO 7-92 8-76 abt. 300 



CaO 1400 12-60 7-17 



Na.,0 2-28 1-45 491 



K,6 1-51 "M 201 



H" 2 100 0-30 abt. 030 



P.fO, Trace Trace 0'76 



CaC0 3 Trace Trace 



100- 16 10081 abt. 100-99 



I. Olivine-gabbro-diabase of Brandberget; analysis by L. Schmelck. 

 II. Do. of Solvsberget; analysis by Sarnstrom, the alkalies determined by 

 L. Schmelck. 

 III. Do. of Dignses ; analysis by A. Damm, the alkalies determine 1 by 

 L. Schmelck. 



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