50 
Kex T. Pridek. 
seJiist. The prosciu-e of similar tjuartz-scririlo rocks associated with the 
north-west system of (juartz veins, whi('h in view of their disposition in the 
field, cannot be regarded as infolded poi'tions of the Cardup slates, would 
ai)pear to indicate that botli gr()iu)s ol veins arc* of similar origin, i.e., 
replacements along shear zones. This is supt)orted by the absence in the- 
vicinity of the <]uartz blow at the south end of the aiea of other remnants of 
tlie (hirdLi]> seric's, for if the slates were infolded then a considerable ])ortion 
of the more ar-fmaceous sediments underlying them must also hav(' been 
infolded— no (race of these remains and the evidence is oxa'rwhelmingly 
against the possibility that this band represents nxi infohh'd portion of the 
(hirdiip slates. 
A similar (juartz vein in the granitic gneiss near the contact with the 
sediments of tlie (lardup S('ries has been noted near Kelms(mtt. This occur- 
rence is exposiul in a small road cutting on a ron<l leading east from the 
lownsite. The exact position of tin* sediment-granite contact cannot be 
located as exposures are vei'y weathered and poor. The slaty Cardup rocks 
are ('x|)os('d in sevau'al small ])its and, as at Armadale, dip steejily to the 
west. The granite contact lies ap])roximately 200 feet east of tlies(^ pits 
and about 200 fe(*t east of tin* contact there is a (piartz vein which stiikes 
200^ and di]is stet^ply to the east. It is bordered by sheared material which 
at lirst sight appt'ai’s to be slate but when closely examined is seen to have 
a ^densy'’ structure and not the well ])edded character of the slate. Although 
the mat('rial was too weathered for microscopic examination it appears to 
be a sheaix'd granitic rock rather than the Cardup slate and the occurrence 
is remarkably similar to that at Armadale. The shear zone in the Kelmscott 
occurrence is ai)])voximately 10 yards wide. 
Returning to a eonsideration of the large ((uartz blow^ — -in places it 
has a handed a])pearauce where the quartz has been injected along the 
schistosity planes of the serieite schist (plate 2, fig 2A). Bdow the surface,. 
th(* vein is represented by a quartz musco\'ite rock not unlike a fine grained 
greisen, the muscovite here having been recrysiallised. Tlie massive quartz 
of the vdn has ail been strained (filate 2, fig. 2B) and is, in this respect, 
similar to that of the north-w('st grou]). This straining may have been 
etfected during the movements which tilted the Cardup Series. 
All the (‘vidence avaihilile, both chemical and petrological, suggests 
that the north-wi'st and north groups of quartz veins in the gneissie rocks 
are similar in diaraeter and Avere formed during the same period along 
shear zom^s which are developed in a regular pattern and that these veins 
were* sul)j(‘cled to post-crystallisation stress. 
Tuiaiing now to a consideration of the quartz veins in the Cardup 
slates — no actual vein in situ was seen in this area, although the presence 
of heaps of (puirtz fragments in the slate quarry indicates its presence. 
Cam])bel! (1910, p. 29) describes these quartz masses as “bunches of quartz 
veins up to 18 inches diameter.” They are probably similar to a larger occur- 
rence of vein quartz in the slates at Cardup, some miles to the south (Clarke, 
1930, map on p. Ififi). The (puirtz from the Armadale slate (piarry is fine, 
even grained, wdiite, and under the microscope is seen to be an eiiuigranular 
aggregate of allotriomorphic grains (Plate 2, fig. 2(;') which have not suf- 
fered any post-crystallisation stress. This vein material therefore appears to 
have been formed at a later period than the quartz veins in the granitic 
rocks (which all show stress effects). The veins in the slates appear to be 
