540 N. L. BOWEN 



escape from the conclusion that it will nonnally be saturated. The 

 normal effect of granite upon more basic inclusions should therefore 

 be such as has been outlined above. Thus we find that Fanner, in 

 describing the action of granitic magma on basic bands in an injec- 

 tion gneiss, says, "In other places the dark minerals appear to have 

 been taken up or digested by the magma and to have crystallized 

 out again in large blades. Even in the latter case it is not always 

 certain that perfect solution has been effected at any one time. The 

 process may have been rather in the nature of a chemical reaction 

 with the original minerals or the solution and redeposition of a por- 

 tion of the material at a time,' leaving the general relations undis- 

 turbed. This possibiHty is suggested by the fact that frequently 

 even the coarser micaceous blades or aggregates of dark minerals 

 show evidence of parallelism and this would be difficult to account 

 for under the supposition that solution was so perfect that the 

 original structure was completely wiped out."^ Here, apparently, we 

 have a good example of the transformation, by reaction rather than 

 solution, of the dark bands into mica-rich material, mica being the 

 dark mineral with which the magma is saturated. The change of 

 serpentine into biotite as observed by Gordon at the borders of 

 granitic pegmatites is precisely the action to be expected.^ 



V. M. Goldschmidt describes the strewing about of the minerals 

 of a basic hornfels in magmas of the Christiania region. He says, 

 '' This strewing about hardly has its origin in a solution of the miner- 

 als and their later separation. Had solution occurred the grains 

 would not have retained their original forms and they would have 

 differed in composition from the minerals of the hornfels." Near 

 the border of an apophysis of the nordmarkite, grains ofdiopside 

 from the hornfels are surrounded by a rim of aegirite. In the center 

 of the apophysis the aegirite has no core of diopside.^ 



^ Note discussion on p. 532. 



2 C. N. Fenner, "The Mode of Formation of Certain Gneisses in the HigUands 

 of New Jersey," Jour. Geol., Vol. XXII (1914), PP- 602-3. 



3 "Desilicated Granite Pegmatites," Froc. Acad. Nat. Sci. Phila., Part I (1921), 

 p. 169. 



tV. M. Goldschmidt, "Die Kontaktmetamorphose im Kristianiagebiet," Vid. 

 Selsk. Skr. I. Mat. Naturv. Klasse (191 1), No. r, pp. 107-8. 



