10 
MUSEUM BULLETIN NO. 30. 
gabbro in small, rounded lumps, 6 inches to a foot in diameter, 
which grade rapidly into the gabbro, The impression gained from 
field observation was that these feldspathic patches were 
apophysal in their nature, produced by the action of aplitic 
solutions on the normal gabbro. However, under the microscope 
it is clearly seen that the feldspar is highly calcic, instead of 
sodic as might be expected under the latter hypothesis, and the 
component minerals show no sign of being other than primary 
crystallizations, so the conclusion is inevitable that these bodies 
are really small segregations of anorthosite which were in process 
of separation from the molten magma when solidification took 
place. 
Granite. 
Granite is relatively very small in amount, and, as men- 
tioned, is found only on Possession point, at the southwest cor- 
ner of the peninsula. The main mass lies almost horizontal, with 
a low dip to the north, and is some 30 feet in thickness. It is 
very clearly intrusive into the complex of gabbro and Metchosin 
basalt that occurs here, which is penetrated and brecciated by 
long strings of granite. 
The granite is a light, greenish-white rock, weathering to a 
brownish-white, with an average grain of less than 1 mm. It is 
composed of approximately 20 per cent quartz, 70 per cent oligo- 
clase feldspar, Ab 85 An 1B , 6 per cent hornblende, and accessory 
amounts of magnetite and titanite. Many of the feldspars show 
zonal banding. 
Dykes . 
As already mentioned, the dykes are of two main types, 
gabbroid and granitic, although there are many sub-types, due 
to minor variations of composition and texture. The dykes 
usually have wide chilled edges, indicating that the gabbros into 
which they were intruded had become fairly cold. 
The gabbroid dykes may. be subdivided into the porphyritic 
and non-porphyritic types. The latter are of a basaltic compo- 
sition, equigranular, and basaltic to gabbroid in texture accord- 
