300 



Wark gabbro-diorite gneiss. One half mile south of Mt. 

 Tolmie, Victoria district. M. F. Connor, analyst. 



Fine grained phases of the Wark gneiss occur as segre- 

 gations or inclusions in the normal rock, especially near 

 the contacts with the intrusive Colquitz gneiss and Saanich 

 granodiorite. In places they form bands parallel to the 

 foliation, but more commonly they form irregularly shaped 

 masses sometimes several yards in width, which fre- 

 quently are elongated in a direction transverse to the 

 foliation. The normal gabbro-diorite is not only gneissic 

 but considerably altered and more or less metamorphosed, 

 especially near the contacts with younger granitic rocks, 

 where there have been developed certain metamorphic 

 varieties with large and frequently poikilitic hornblendes 

 or varieties in which recrystallized hornblende greatly 

 predominates. 



The Colquitz gneiss is a gray, medium grained rock of 

 gneissic to schistose texture, consisting essentially of al- 

 tered plagioclase (andesine), quartz, hornblende, and 

 biotite, and is classed as a quartz diorite although it 

 contains much more quartz than the average quartz 

 diorite. At one locality the gneiss is a biotite granite. 

 The Colquitz gneiss has also certain salic and femic fades. 

 The salic facies is light coloured, consisting essentially 

 of quartz and feldspar, while the femic facies is dark, 

 consisting almost entirely of hornblende, thus forming 

 hornblendites. The facies commonly occur interbanded, the 

 separate bands or masses varying from a fraction of an 

 inch up to several feet in width, thus producing a con- 

 spicuously banded gneiss. The larger femic bands are 

 virtually always coarsely crystalline. 



The following analyses are of the Colquitz gneiss: — 



Si 2 64-04 75-02 



AI2O0 15-83 13-90 



Fe 2 3 2- 16 0-45 



Fe 2-40 0-40 



Mg 2-72 o- 10 



Ca O 3-6o 



Na 2 3-52 



K 2 1-43 



H 2 + 1 -6o 0-95 



Ti 2 0-30 0-04 



•16 

 ■06 



•37 



38 



12 



6 



8 



13 

 11 

 1 

 o 

 2 

 1 



80 

 50 



57 

 20 

 10 

 42 

 60 

 81 



85 

 60 



