On the Formation of Pegmatite. 33 



On the Formation of Pegmatite Veins. 



By Prof. W. C. Brogger, of Stockholm, Sweden. 



(Translated from ** Die Mineralien der Syenitpegmatitgange der 

 siidnorwegischen Augit und Nephelinsyenite," by JSevil 

 Norton Evans, M. A. Sc.) l 



As reviews of the older opinions with regard to the ori- 

 gin of pegmatite veins have already been presented by 

 several authors, 2 it seems to me unnecessary to refer to these 

 in detail, and I shall, therefore, leave unnoticed those which 

 have no probability and which are held by no one at the 

 present time, 3 and consider only the principal and more 

 rational views concerning them. 



Many of the older authorities considered pegmatite veins 

 to be simply eruptive injections ; to them, acid granitic 

 pegmatite veins were almost the only ones known, and 

 therefore their statements refer almost entirely to such acid 

 veins. Charpentier, in 1823, (in his " Essai sur la constit. 

 geogn. d. PyreneV') expressed the perfectly correct view, 

 according to my opinion, that the granite pegmatites are 

 fissure-veins " which were formed immediately or very soon 

 after the solidification of the granite enclosing them" 

 (quoted from Naumann, 1. c, p. 232) ; they were, therefore, 

 " injections of granitic material, which, originating in the 

 still fluid granite deep down, were pressed into the cracks 

 of the already solidified granite above — after-births, as it 

 were, of the same granite formation in the district of which 

 they occur." (Naumann, 1. c.) 



1 One of the most important contributions which has been made in recent years 

 to our knowledge of the igneous rocks, is the summary by Prof. Brogger, of the 

 results of his admirable and long continued studies in the Christiania district, 

 which appears in the first part of this book. As the question of the true origin of 

 pegmatite veins is one of great importance to the right understanding of many 

 facts in connection with our Archean geology, it has been thought well to present 

 a translation of the chapter which deals with the general conclusions reached by 

 Prof. Brogger concerning these veins, referring the reader to the monograph itself 

 for a detailed statement of the evidence on which these views were based. 



2 e. g. C. F. Naumann, " Lehrbuch d. Geognosie," 1862, 2, 231-233 ; F. Klock- 

 mann, " Beitrag z. Kenntn. d. granit. Gesteine d. Riesengebirges," Zeitschr. d. d 

 geol. Ges. 1882, 34, 405-406, etc. 



3 With regard to the views of Alluaud, Ramond, Came, etc., see Naumann, 1. c, 

 p. 232; with regard to Garrigous's views, see Bull. d. 1. soc. ge"o). d. France, Ser. 

 III. 8,11 



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