SOUTH CHETICAMP, CAPE BRETON ISLAND. — GRANDIN. 355 



are of considerable but undetermined thickness. Tlie McLeod 

 rocks possess somewhat similar lithological characteristics to 

 those of Grandin brook and like the latter carry metallic 

 sulphides disseminated through most of their beds. There is, 

 however, as a rule, a marked difference in the nature of the 

 sulphides carried by the two groups. Arsenopyrite, which is 

 the dominant ore of the McLeod rocks, is conspicuous by its 

 absence in the " copper schists." The nature of the rocks 

 overlying the deposit has not yet been determined, as the hang- 

 ing wall has not been reached ; but the data so far collected 

 indicates they possess characteristics similar to the underlying 

 beds. The " copper schists " at their outcrop in the Grandin 

 brook sti'ike N. N. E. and S. S. W., with an average dip of 

 45"^ to the E. S. E. ; but owing to the axis of the fold pitchino- 

 S. S. W. at about an angle of 10, the deposit is tilted up 

 towards the north at its outcrop in the McLeod cliffs and then 

 it has been ground down by detritive agencies to a thickness 

 of about 40 or 50 feet. The characteristic cross-folds and 

 contortions of the L'Aibme schists are well illustrated at the 

 deposit. Fig. 1 gives some idea of the tumultuous nature of 

 the smaller contort ions. The same pressure which produced 

 the cross undulations, not only caused horizontal displacement 

 of the beds, but caused the layers to slide over each other, by 

 which movements cavities were developed. Many of these 

 cavities have no doubt been modified in shape by the corrosive 

 action of circulating fluids, but their original shape has generally 

 been fairly well preserved. Figs. 2 and 3 represent the man- 

 ner in which the lens-shapes were produced. Fig. 2 represents 

 the corrugated beds before, and Fig. 3 after the sliding move- 

 ments had taken place. This structure is characteristic of all 

 the L'Abime deposits ; but is not so well illustrated at Grandin 

 brook as at Iron Cap and Galena, as owing to the minuteness 

 and the great abundance of the contortions of the " copper 

 schists " the lenses are usually extremely small. Fig. 4 shows 

 another structure, common to all the deposits, which has been 



Proc. & Trans. N. S- Inst. Sci., Vol. XI. Trans. X. 



