Tiik Contact Bktwekn the Granitic Koctcs ani» the Cardup Series 
AT ARilADAEE. ol 
closely related to a thin seam of siliceous concretions which are developed 
alon^ the east wall of the lower bench in the puarry (tig. 2)— these concre- 
tions occur as llattened ellipsoidal bulges averaging 9 inches diameter, 
projecting from the bedding surface. They have a coiu'entric structure, 
are cut by numerous intersecting joints and are com|K)s(‘d almost entirely 
of line grained (luartz. The texture is allotriomorphic granular, similar to 
that of the quartz veins but mucb liner in grain (average grain size of 
concretions O.Od mm. diameter while that of the veins averages 
9.15 mm.). Although exposures here do not p(‘rmit a definite 
pronouncement tliat the concretions and quartz \-('ins are gen(*fically related 
it appears probable that the V(un material re])resetits a more complete segre- 
gation and coarsei' crystallisation of the silica than tlu^ ('oncretions atul that 
both have be(m formed liy the same process. It is lutped that further light 
will be thrown upon the origin of these veins by woi’k now in progress by 
Mr. B. Thomson in the Cardup area. One jioint however is (dear — that the 
quartz veins in the slates are later than those in th(‘ granitic rocks and have 
not been straimal during the movermmts whi(di alTected the Cardup Series. 
Other rcHi.s: — In the east wall of th(‘ slate (luarry souu* very thin vein- 
lets of barite W(n*e noted in the highly weathered rock which appears to 
l>e one of the basic intriisives. This o('(nirrcnec is inteivsting sinc(‘ it throws 
some light on tli(‘ origin of th(‘ harite-tluor veins in the (hirdui> Series at 
Cardup (Clarke, 1930, map on i>age 199) — it indi('ates that the barite vOns 
are later than the basic intrusives and were ihend’or*' i)rohahIy derived from 
the greenstone magma rather than tiie granitt* magma. It is interesting to 
note here that Sweet (1930, p. 258) considers that the barite ami fluor 
bearing veins of the iiorlli of Bngland arc* genetically related to tin* (juariz 
dolerites of the Whin Sill. 
On the south si<le of the Bedfordah* Hoad (outside tin* area desca'ilx'd 
in this pjqier) ([uartz veins containing smail amounts of gah‘na and 
s])halerite have* been fonnd. Tlu*se occurrtmees have not b(*(‘n (dosely ex- 
amined hut they ajipear to he similar to the silver-lead d(‘])osits of Muudijong 
(Esson, 1927) whidi are (dosely associated witli a iiorphyi’it ic- albite (‘pi- 
diorite (albite i>orphyrite of Esson) which is similar to tlu' alhitc cpidiorilc 
from Armadale. The suggestion is put foiuvard Inwe that these silver-l(*ad 
veins and barite-lluor veins are genetically related to the liasic magma ratlu'r 
than to the granitic- magma. 
TV. CONCLUSIONS. 
(a) The age of the (lardup Series. 
The evidence* in'(*scnt(‘d by tlie (piartz veins (both in tlu'ir tield relations 
and petrology) indicat(*s that the* granitic* rocks are o]d(*r than the Cardup 
sediments. This conclusion is sup])orted hy a number of otlic'r facts — (i) 
that the Cardup Series is a normal erosion seciuenc'e and is constant in 
character along the strike; (ii) that nowhere have the* “.uratiil ising'^ solu- 
tions been seen to traverses the basal f)cds of tlie seri(*s nor have any 
aimphyscs (sncdi as p(*gmatites or (|uartz veins) heem seen to jiass into the 
sedimc'nts; (iii) that tliere are no remnants (x(*nolitlis) of the sc'dimentary 
series in the gneisses, the only rc^mnants being of oldc*r basic igneous rocks; 
(iv) that no variation in character of the gneiss across the strike, sueh as 
would be expected if a series of varying lithology were granitisc'd, has h(*(*n 
noted, and (v) the slight eontacd metamorphic cdleGs noted in the Cardup 
Series ai’c* due to the* basic- intrusions. Indeed, the only evidence that has 
