The Contact Between the Gkanitic Ro(.ks and the Cardup Series 
AT Armadale. 49 
of sericitic mica. This dark coloured material, xenolithic in the vein quartz, 
was analysed and the analysis is shown in table VI., and it will be seen 
Table VT. 
1. 
2. 
3. 
4. 
SiO,... 
... 47-54 
43-37 
65-22 
65-22 
... 29-01 
33-19 
19-22 
16-71 
Fe.iO-j 
... 3-59 
1-95 
2-38 
1 -93 
Feb 
1-33 
1-00 
0-88 
3-23 
MgO 
1-53 
1-36 
1-01 
2-87 
CaO ... 
... Nil 
Nil 
Nil 
0-05 
Na.>0 
... 0-09 
1-03 
0-06 
0-76 
KoO... 
... 10-25 
10-17 
6-79 
5-98 
H.,0+ 
... 4-42 
"Loss on 
2-93 
2-12 
H.O~ 
... 0-06 
f ^ 
ignition. 
004 
0-16 
Cbo ... 
... 0-03 
• » • 
0-02 
0-05 
Tib.2 
... 0-85 
0-33 
0-56 
0-35 
Poo; 
... Nil' 
• • . 
Nil 
0-08 
MnO 
... 0-12 
• • • 
0-07 
0-03 
BaO 
... 1-01 
. . . 
0-67 
0-11 
Cr,0, 
... 0*02 
0-02 
0-01 
VoO, 
... 0-13 
« • « 
0-08 
0-03 
SO, 
... 0-07 
005 
O-ll 
0-05 (Graphite) 
100-05 
100 14 
100-00 
99-85 
Analyst 
H. P. Rowledge. 
C’. R. Le IMesurier. 
1. Sericite schist (19481), (dark patches xenolithic in quartz vein, from which 
all vein quartz has been removed), near Bedfordale Road, Armadale, 
Anal. IT. P, Rowledge. 
2. Muscovite, Bamle, Norway. {Amer. Jour. 8c., vol. 24^ p. 259, 1959). 
3. Analysis 1 with 8iO^ made up to 65.22% and the remaining oxides recalculated 
to sum to 100. 
4. White shale, Armadale, Western Australia (quoted from Table II.). 
that it is very siinilai* to the analysis of muscovite. A noticeable feature of 
the analysis is the high baryta content, and the presence of very little SO 3 
indicates that it is not in the foian of barite but must l>e in the mica.. No 
barite was visible in the thin sections examined. Floaters of this sericitic 
material can be traced for some distance in a northerly direction and this 
appears to be a shear zon(‘ in the granitic rocks along which I'eplacement 
quartz veins have been formed. The other possibility is that (his band of 
sericitic material is an infolded portion of the Cardu]i slatt^s along which 
quartz has been introduced. Comparing the analysis of the sericitic material 
with that of the white slate (table VI, col. 4) the main diftereiice is seen 
in the amount of SiO.. Jf silica is added to the sericite schist to bring it to 
65.22% and the remaining oxides recalculated to sum to 100 (col. 3) there 
is seen to be a close agreement, the mai?i differences being in llu' higher FeO 
and MgO in the slate (due to chlorite), the different pi'oportions of the 
alkalies and the higher BaO content of the sericite schist (this seems to be 
a significant feature as the BaO in the sericite schist must he in the mica— 
in this connection it is interesting to note the comparatively high BaO 
content of the hybridised gneiss in tabh* I.). It must be noted that the 
products of sericitisation of alkali felspar are similar to those accumulating in 
certain fine grained argillaceous sediments (especially illitic clays) so that 
a comparison of these analyses, wdiich are both of highly sericitic rocks, 
does not convey any real information regarding the origin of the sericite 
