302 



Saanich granodiorite, south shore of Shoal harbour, 

 North Saanich district, M.F. Connor, analyst. 



The diorite porphyrites usually form fairly well defined 

 and regular dykes, from a few inches up to 50 feet (15 m.) 

 in width, largely confined to the vicinity of the contacts 

 of the Esquimalt stock. They are greyish green, porphy- 

 ritic rocks, with an aphanitic groundmass and phenocrysts 

 of feldspar, hornblende, and sometimes augite. 



All of the irruptive rocks have been more or less foliated, 

 the gneisses greatly. The strike of the foliation is predomi- 

 nantly northwest-southwest, generally near N. 6o° W, 

 but varies widely. The rocks are also greatly jointed and 

 fractured, and in places sheared. They are altered and, 

 especially near the shear zones, are mineralized and cut 

 by small and irregular quartz and quartz-epidote veins, 

 but contain no mineral deposits of commercial value. 



Although the Wark and Colquitz gneisses form virtually 

 a single batholith, the Colquitz gneiss is distinctly intrusive 

 into the Wark gneiss, the contacts being marked by wide 

 zones of shatter breccias and numerous aplitic and a few 

 pegmatitic apophyses of the Colquitz gneiss. Although 

 in places cross cutting, the apophyses are usually injected 

 parallel to the foliation, and are foliated themselves par- 

 allel to their walls. In some instances the apophyses, 

 parallel to the foliation, are so numerous as to convert the 

 gabbro-diorite gneiss into a banded gneiss resembling the 

 banded Colquitz gneiss. Also the Wark gneiss is cut by 

 large masses of the Colquitz gneiss, usually the salic facies, 

 some of which are several hundred feet in width. The 

 contact zones are sometimes sheared and foliated and the 

 angular xenoliths of the gabbro-diorite gneiss in the quartz 

 diorite gneiss have been pulled out into dark femic bands 

 These strongly resemble the femic bands of the Colquitz 

 gneiss, but in part perhaps differ from them by being occa- 

 sionally broken or cut across the foliation by the quartz 

 diorite. The relatively few dykes of pegmatite are unfol- 

 iated, and, while usually parallel to the foliation, are 

 sometimes cross cutting. 



The banded Colquitz gneiss, in particular that type 

 with the wide, coarse grained, femic bands or masses, is 

 more or less restricted in its occurence to the contacts 

 with the intruded Wark gneiss. As described, its salic 

 and femic bands vary in didth from a fraction of an inch 

 to 4 or 5 feet (1-2 or 1-5 m.), and possibly to several feet. 



