June 5th, 1914. 
Canada 
Geological Survey 
Museum Bulletin No. 2. 
GEOLOGICAL SERIES, No. 13. 
/. — The Origin of Granite ( Micropegmatite ) in the Purcell Sills. 
By S. J. Schofield. 
INTRODUCTION. 
Of late years, the assimilation-differentiation hypothesis, in 
connexion with the larger problems of petrogenesis, has received 
some measure of support from the study of the gabbro and assoc- 
iated granites occurring as sills in various parts of the world. 
The purpose of this paper is the examination and discussion 
of this hypothesis with reference to the origin of the so-called 
“secondary” granite in sills; especially in those of East Kootenay, 
B.C. This is all the more desirable since the East Kootenay 
sills shov r a general type of phenomena common throughout the 
world, and since they present such exceptional opportunities for 
study. 
The problem was suggested by Professor R. A. Daly of Har- 
vard University and was studied in connexion with the geolog- 
ical mapping of East Kootenay, B.C., during the field seasons 
of 1909, 1910, 1911, and 1912. 
Previously Daly studied occurrences of similar phenomena and 
published several interesting papers. 1 Daly's main conclusions 
are as follows: — 
(1) “The Moyie intrusive is an enormously thick sill composed 
in greatest part of a peculiar hornblende gabbro slightly acidified 
at the lower contact. An equally abnormal biotite granite 
1 DaIy, R. A., Geol. Surv. Can., Ann. Rep., 1904, p. 91A. 
Daly, R. A., Amer. Jour. Sci., vol. 20, 1905, p. 185. 
Daly, R. A., Festschrift zum siebzigsten Geburtstage von H. Rosenbusch, 
1906, p. 203. 
56815—1 
