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been called the Wark and Saanich periods. During the 

 first period, the Wark and Colquitz gneisses were irrupted, 

 but independently, thus dividing the Wark period into 

 two sub-periods, the second sub-period being characterized 

 by the irruption of a more salic magma than that irrupted 

 during the first. The close relationship of the Wark to 

 the Colquitz gneiss shows, however, that they are closely 

 related in origin, and are doubtless differentiates of the 

 same parent magma. A similar subdivision characterizes 

 the Saanich irruptive period, but the first sub-period, 

 during which the femic Beale diorite was irrupted, is not 

 well represented near Victoria. Also the rocks irrupted 

 during the Wark and Saanich periods are closely related 

 structurally, and, except that those of the Wark period are 

 gneissic, are similar lithologically. It is probable, there- 

 fore, that the Wark and Saanich magmas were themselves 

 differentiates of the same parent magma, the Wark magma 

 being more basic then the Saanich magma. Since the 

 principal rock types have been separately, and more or 

 less independently, intruded in large masses, the differ- 

 entiation producing the various types must have been 

 deep seated. Since the parent magma was apparently 

 subdivided into the Wark and Saanich magmas, each of 

 which independently underwent further differentiation 

 under deep seated conditions, it seems probable that this 

 differentiation did not take place in the same magma 

 chamber. It looks as if the Wark and Saanich magmas 

 after differentiation from the parent magma were irrupted 

 from the primary magma chamber into separate chambers, 

 where each underwent its further differentiation, producing 

 the sub-types which were themselves irrupted independ- 

 ently into their present position. It also appears as if the 

 three principal types were still further differentiated, 

 apparently "in place", giving rise to the minor variations 

 of the principal rock types. 



Metchosin volcanics. — Confined to the western part 

 of the region and separated from the other crystalline rocks 

 by the thick deposit of sand and gravel of the Colwood 

 delta, are the Metchosin volcanics. They are all basic, 

 chiefly basalts and diabases, the latter occurring as dykes 

 in the basalts. The basalts vary from coarsely porphy- 

 ritic and ophitic varieties to amygdaloids, and frequently 

 exhibit pillow and columnar structures. They are inter- 

 bedded with fragmental varieties, ranging from fine tuffs 



