346 R. A. DALY THE OKANAGAN COMPOSITE BATHOLITH 



worked their way through the rock in its mechanical readjustments.* 

 Escape for the mineral-laden fluids was most ready in the zones of maxi- 

 mum shear. Thither the fluids were drawn, and there some of the dis- 

 solved material recrystallized so as to develop the darker colored bands of 

 biotite-epidote gneiss, biotite schist, and hornblende gneiss. 



Where the granulation was least the granodiorite retains nearly its 

 original composition, though epidote may be formed; the specific gravity 

 averages 2.746. Where the granulation was more pronounced, as in the 

 first metamorphic type described, much of the hornblende, titanite, mag- 

 netite, and apatite have been leached out and abundant metamorphic bio- 

 tite and epidote have formed; the result is a biotite-hornblende-epidote 

 gneiss with a density less than that of the original granodiorite because 

 of the loss in heavy constituents (specific gravity, 2.692). A further 

 stage of granulation and energetic shearing led to the formation of per- 

 fect schistosity in rock made up of the quartz-feldspar ruins of the orig- 

 inal rock, cemented by very abundant biotite and epidote — the biotite- 

 epidote gneiss (specific gravity, 2.783). The fissures and fluid-filled 

 cavities developed in the zones of maximum shear are now occupied by 

 the strongly schistose hornblende gneiss (specific gravity, 2.939) and sim- 

 ilar products of complete solution, migration, and subsequent complete 

 recrystallization. 



The granodiorite has thus become not only mechanically crushed, but 

 to a large extent rendered heterogeneous. It is now not only gneissic, but 

 banded in zones of new rock markedly varied in composition. The schis- 

 tosity and banding everywhere agree in attitude; the strike varies from 

 north 10 degrees west to north 75 degrees west, but over large areas, as 

 indeed over the whole batholith east and west of Osoyoos lake, averages 

 north 45 degrees west almost exactly. Neglecting minor crumplings, the 

 dip varied from 70 degrees northeast to 90 degrees, averaging about 82 

 degrees northeast. This average attitude is close to that observed in the 

 schists cut by the granodiorite, but represents an exceptional strike among 

 the main structural axes of the Cordillera. It may be noted that shear- 



*This conclusion has in this instance heen deduced from the study of thin-sections. 

 In general it accords with the results of experiment. M filler has found that in carbon- 

 ated water hornblende and apatite are much more soluble than either orthoclase or olig- 

 oclase. Magnetite is less soluble than any of those minerals, but the relatively minute 

 size of its crystals in granodiorite would allow of its complete solution and migration 

 before the essential minerals had lost more than a fraction of their substance. It is 

 also possible that magnetite would suffer especially rapid corrosive attack from fluid in 

 which the chlorine-bearing apatite has gone into solution. Cf. R. Muller in Tschermak's 

 Miner, und Petrog. Mittheilungen, 1877, p. 25. 



