248 
C. E. S. Davis. 
III. 
STRUCTURE AND DISTRIBUTIOX OF THE ROCKS. 
A. Xeiioliths. 
Small fairly equidimeiisional fragments of more basic rock have been 
found m the granite. Some of these .xenoliths are gneissie, but the orien- 
tation of^ their banding is very irregular. In sine they range from large 
masses 15 teet aeros.s to almost entirely assimilated wisps, so that some of 
Ihe specimens classed in the Held as “granites” may actually be hybridised. 
There is also a large doubtfully .xenolithie elongated body found near 
the edge <)f the granite, north of Ellis Brook, which is shown on the map as 
“Chloritic Schist.” Its borders have been weathered away, so that its rela- 
tion with the granite and basic dykes cannot directly be determined. The 
schist trends a little to the we.st of north, and contains several irregular quartz 
veinlets which in general strike north-south and dip east v(>ry steeply.^ 
(Quartz veins, about two feet wide, may be traced from the granite into tlie 
schist. They resemble other quartz veins from the area, whhdi, it will be 
shown, were formed at a late stage in the cooling of the granite. Thus, the 
schist existed before the granite had completely cooled, and it is probably 
a xenolitJi in sj)iu* of its dyke-like outcrop. 
Although large number of xenoliths was noted near Gosnells, they 
are actually imsigniticant in bulk compared with the host-rock, and, except 
£oi the chloritic schist, these small masses are not shown on the uiap. In- 
numerable xenoliths are found at Armadale (Prider, 1941, p. 29) and small 
xenolithie fragments occur in the granite as far north as Stathands (Clarke 
and Williams, 192(), p. 1()9). 
B. Granite. 
The granite of the area is nearly all massive, and even in the better 
exposures in the (piarries no flow structures were detected (although these 
may have been largely obscured on the stained joint-surfaces forming the 
walls of the quarries). Faint flow-layers (and, in two places, flow-lines) are 
found in isolated outcrops and boulders in the extreme south and in the 
north-east. The strike of the flow-layers is east of north, but very variable, 
and their dip is to the east at 40° to 70°. 
It is imiiossible yet to say whether the massive granite grades into or 
intrudes the more gneissie granite of the south of the area. Mapping and 
detailed ])etrological examination of the country immediately to the south 
may reveal whether the granites are the same or dilferent. 
C. Acid I^itrusives into Granite. 
Dykes of aplite and pegmatite cut the granite, but they are too short 
and thin (none was over two feet wide) to be noted on the map. 
(Quartz veins have also been found, and they intrude the pegmatites. 
They usually outcrop strongly, and many of them are large enough to be 
shown on the map. Near most (luartz veins, tin* granite is altered and has 
been weathered away. The edge of the quartz ‘‘blow” shown on the map is 
the edge of a zone of decomposed granite throughout which quartz veins 
occur. 
Thin quartz veins (from an inch to three feet wide) have a general 
north-south trend (of 22 directions measured, 14 lay between 340° and 40°). 
Such thin quartz veins, however, rarely persist for over a chain. A larger 
