PYROXEXITES OF THE GRENVILLE SERIES 323 



sections of small offshoots from the main mass which have thrust 

 themselves in between the beds of quartzite and were subsequently 

 exposed by the planing down of the surface. Ells cites a number 

 of cases where the pyroxenite cuts the stratified gneiss. At Little 

 Rapids mine on Lievre River the pyroxene dike is said to cut the 

 banded gneiss at an angle of 30° or more. At North Star mine the 



S^ \ ^ \ N N V N S 



s^'^'^NNX^ \N 



J l^-^y-^-^l P y t* o X e VL li- e. . 



Fig. 5. — Bowlder of country rock imbedded in pyroxenite, High Rock mine, 

 Ottawa county, Canada. (After Penrose.) 



gneiss has been heaved up and bent around a portion of the dike, 

 the contact of the two being sharply defined. A similar occurrence 

 has been figured by Professor Penrose.^ 



That the pyroxenite should so often occur in sheets alternating 

 with the quartzite is not strange, considering the extent of disturbance 

 which these appear to have sufi'ered and the more favorable con- 

 ditions afforded by the bedding planes for the passage of the lava. 



Further, and it would appear conclusive, evidence of the erup- 



^ R. A. F. Penrose, "Nature and Origin of Deposits of Phosphate of Lime," 

 U. S. Geological Survey, Bulletin No. 46, p. 25. 



