163 



and in a few cases sillimanite was observed. The pre- 

 dominance of mica gives the rock a light silvery grey, 

 shining lustre. The coarse, crystalline varieties of anda- 

 lusite and staurolite schists are found mostly at the eastern 

 end of the field, while the coarse hornblende schists are con- 

 fined to the western end where they sometimes attain a 

 great development. 



In the metamorphosed zones surrounding the granite, 

 every gradation from unaltered slates and quartzites to 

 completely recrystallized schists and gneisses are noticeable 

 as the granite is approached. 



A slight amount of metamorphism, due to dynamic 

 action, is also developed locally along the axes of some 

 of the sharp folds where the rocks have suffered great 

 compression, and this is specially noticeable in the eastern 

 end of the field where the strata are more closely folded. 



Structural Relations. 



The importance of a knowledge of the structure of the 

 Goldbearing series will be generally conceded when it 

 is understood how intimately bound up with the geological 

 structure is the distribution of the ore deposits. The 

 unravelling of the structure is by no means easy. Only 

 one horizon, the boundary between the Golden ville and 

 Halifax formations, can be traced throughout the field, 

 but, while in the east this boundary is sharp and distinct, 

 in the west it is not nearly so distinct. The structure of 

 the Goldenville formation is generally more easily deciph- 

 ered than that of the Halifax in which the cleavage of 

 the slates is often so much developed as to obliterate 

 nearly all traces of stratification. Traverses made across 

 the series from north to south show a succession of alter- 

 nating zones of the Halifax and of the Goldenville forma- 

 tions varying in width from a fraction of a mile to several 

 miles. A close study of the structure of these zones shows 

 that the strata are closely folded in a series of long parallel 

 anticlines and synclines, the tops of which have been 

 extensively eroded. 



In the eastern part of the field the width of the quartzite 

 zones is generally much greater than that of the slate, 

 while in the western part, the two formations are more 

 nearly equal in width. In the eastern half these zones 

 extend in a general east and west direction, while in the 

 35063— 1 1 § 



