phalen] the rocks of nugsuaks peninsula 187 



dislocations have occurred in certain portions of the elevated mass 

 is evident from the foldings exhibited in the dark intercalated layers 

 in the granite. These horizontal dikes of diorite, for such they prove 

 to be, present many phases, as present in the Museum collection, 

 ranging from the finest grain in the lowest to a pegmatitic facies. 

 In every case the structure is decidedly schistose, traceable to the 

 shearing action consequent to earth movements. 

 An analysis of this granite follows : 



Analysis of Granite. (W. C. Phalen, Analyst.) 



SiO. .■ 76.03 



AI2O3 12.02 



Fe.Os 69 



FeO 68 



MgO 18 



CaO 1.61 



NasO 2.97 



K,0 %72 



H2O 20 



TiO^ 28 



100.38 



The granite needs no detailed description, agreeing so far as con- 

 stituents go with the granites previously described. Like these, it 

 contains the four feldspars, orthoclase, microcline, albite, and oligo- 

 clase. The albite frequently exhibits perthetic intergrowths with 

 both the potash feldspars. Granophyric groups were also noted. 



Diorite. — This rock (Cat. No. 75,481), constituting the lower 

 dark zone in the central elevated mass of the island, might on casual 

 inspection be called amphibole schist, for it has a decidedly laminated 

 structure, produced by a similar orientation of its two essential 

 components, amphibole and feldspar (for such the lighter mineral 

 proves to be). The amphibole occurs in elongated, lath-shaped 

 forms with glistening cleavage plates and is perfectly fresh. Asso- 

 ciated with it in a very few places occurs a greenish mineral, prob- 

 ably chlorite, though no such mineral was observed in the thin sec- 

 tions studied. 



In spots the crystallization of the amphibole is much coarser than 

 the average. Here it is associated with feldspar, also of coarser 

 grain, producing a pegmatitic facies. An occasional grain of pyrite 

 was observed on the fresh fracture, and an occasional garnet also 

 was noted. 



Under the microscope the amphibole proves to be the light green 

 variety, hornblende. It occurs in continuous masses, with splendid 



