ASSIMILATION OF THE SYENlTE-GRANlTE; MAGMA 261 



A few years ago Daly^^ worked out an elaborate magmatic stoping and 

 assimilation hypothesis according to which the intrusions of many great 

 acidic, batholithic magmas have been accompanied by extensive assimi- 

 lation of stoped blocks of invaded rock. 



Van Hise^^ admits that cases of local fusion or absorption of frag- 

 ments or borders of invaded rocks by intruding magmas are known, but 

 he does not believe any proved case of fusion on a large scale is known. 

 Eeferring to Lawson's^^ work in the Eainy Lake and Lake of the Woods 

 districts of Canada, Van Hise dissents from the view that extensive or 

 so-called '^'subcrusta?^ fusion of the invaded rocks has been proved for 

 those districts. 



Adams and Barlow,^^ in an elaborate report on the Haliburton and 

 Bancroft areas of Ontario, say: 



"The further question as to how far granite, having cauglit up inclusions of 

 the rock through which it breaks in the manner described, dissolves, digests, 

 or further acts on them, is one on which it is more difficult to get conclusive 

 evidence. That it does so in some cases is certain." 



They describe several examples where, rather locally, the granite 

 magma has been rendered basic by the solution of amphibolite in it ; but 

 they say that undisputed evidence of such solution on an extended scale 

 has not yet been obtained. The conclusions reached by these two geolo- 

 gists regarding this Canadian region are of particular interest as com- 

 pared with the writer's conclusions regarding the Adirondacks, since the 

 geological conditions are so similar in these two regions. 



Cross,^^ in a review of certain petrological papers, states : 



"That many magmas represented in rocks open to investigation came from 

 depths where the conditions of fusion and assimilation existed is seemingly 

 incontestable. . . . But the assumption that assimilation has taken place 

 generally in large intrusive bodies at contacts now visible is not plain to many 

 petrologists." 



Iddings,^^ in his book on Igneous Kocks, states that : 



"Evidences of absorption by the igneous magma of material from adjoining 

 rocks are very slight, even in cases where these rocks have been profoundly 



28 R. A. Daly : Amer. Jour. Scl., vol. xv, 1903, pp. 269-298 ; ibid., vol. xvi, 1903, pp. 

 107-126 ; ibid., vol. xxvi, 1908, pp. 17-50. 



29 c. R. Van Hise : U. S. Geological Survey Monograph XLVII, 1904, pp. 730-735. 



30 A. C. Lawson : Bull. Geol. Soc. Am., vol. 4, 1890, pp. 185-186. 



31 F. D, Adams and A. E. Barlow : Department of Mines, Canada, Memoir 6, 1910, pp. 

 116-117 and 122-123. 



82 -^7. Cross : Jour. Geol., vol. 20, 1912, p. 364. 

 33 J. p. iddings : Igneous rocks, 1909, p. 282. 



