17 ^ 
rLAKKK AND WiLLiAAiB . — (rrolofjy of D(U'U)>g Range. 
.■). 1 /I trr-i'cl<i I ioll.slii ps of (he has'ic rocks. — 'Flie weij^'lit of ovi- 
d(‘iu'e fa\ours tlio vii'W lluit tlioiH' is not more than one ag'O of 
(‘])i(liofito in tlu‘ tinnis (loscrnu'd. It is true that instances liave 
been seeii of one dylu* faultijig' and displacing another, that the 
surface of contact Ixdv.aan! granite and sonu' dykes is a ‘ Miead ’ ' 
along tvliich the two rocks separate rea.ilily, while in others the 
two rocks ar(‘ so chtsely adherent that th<‘y break more readily 
across than along tlu‘ jiiiicti(ni surface, and that tliere are a few 
dykes which possibly cross tlu‘ shear planes which truncate other 
dykes; but iiuh'ss moi-e comdusive evidence of marked differences 
of age amougsl the dykes is found it is best, in view of their 
p(‘trological identity, t(i regard them as all of substantially the 
same age. In the coinitry jtist east of ['’iesse Brook K. 
h'imicaiu' has found a number of instances of ej)idiorite invaded 
by small dykes and ^'einlets of e])id i(>rit(‘, and also of more acid 
rock. I''iirtlu'r work in tliis neighbourhood Avill quite likely cause 
at h'ast modification of our tentative conclusion as to the single 
age of the ('pidioritt'S, 
D. Quartz reefs in shear-zones. 
The occurr(nice of belts of shearing in the Barling Range 
has long Ikh’u known, but the relation l)etween these zones and 
C(u-tain qiiartzosc^ ro(d\s outcropjiing along the Barling Fault Scar]i 
has not aj)]taiently been recognised. 
The shear zones of the Barlington Area are of two typi'S : 
(I) Sh'ear-zoiies witliout secondaiy (jiuuTz, 
( II ) Shear-zoiu's with ]iartial re]dacemfuit of sheared rock l)y quartz. 
1. A tiii{‘ outcj-op of the fiist type can be seen from the 
)'oad b”) chains S.F. of T>arlington railway station. The ro<di 
luna' is a sericite schist derivi'd from the granite. 
-. A go{)d exposure of the second ty]>e (u-ciirs on the western 
edge of the Area So chains south of the Hehma River, w’hei'e a 
ludt of sluaared granite, associated with a (juartz reef, can be 
traced along tlu' strike for about bOO yards. 
B(‘tailed stmly of this outcrcq) in the field, and the examination 
of thin sin-tioHs, iiidicati' that tin* secondary ([uartz w'as formed 
in jiait liy the mc-tasomati<- rcqdacement of the* original sheared 
granite. 
