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( N:o 1) Igneous Rocks of Sviatoy Noss in Transbaikalia. 5) 
quartz containing drusy cavities with crystals of quartz 
and fluorite. 
Å RT NI SN IVENTI Le SS Je i ” 
Evident as it is that the peninsula of Sviatoy Noss is 
at all sides bounded by zones of displacement, it is no less 
apparent that the peninsula is a broken up part of the vast 
- Baikalian shield, without any geological independence. It is 
neither anticline nor syncline. Its southeastern portion is 
built up of a granite and granodiorite mass which is also 
exposed on the low islands in the Tshivirkouy Bay and con- 
tinues in the Tshivirkouy Mountains and further in the 
 Bargousin valley, having a very extensive occurrence. The 
main part of the peninsula consists of injected crystalline 
schists which are interbroken by displacement at the Tshi- 
-virkouy Bay, but on the eastern shore of the latter reappear. 
According to Kotoulskys map the same rocks continue far 
away towards the north along the shore of Lake Baikal. 
Turning to the geological structure of Sviatoy Noss we 
may at first discriminate those two great complexes: 1) the 
granite-granodiorite mass and 2) the complex of injected 
erystalline schists (see the sketch-map). 
The area of the first-named complex is, for the most 
part, underlain by coarse-grained porphyritic rocks whose 
composition varies between granite and granodiorite. It is 
occasionally intersected by dikes of lamprophyric rocks and 
"very frequently by such of pegmatite and aplite. Aplitic 
granite also forms larger masses within this complex. 
Going towards the boundary of the granite area, these 
-aplitic portions grow more and more frequent and nearest 
SA - 
3 portion of the migmatites, have been invaded by intrusive 
rocks before the intrusion of the granite. These older in- 
oto the boundary towards the migmatitic area there is an : 
almost uninterrupted zone of light grey aplitic granite of 
medium grain. Still farther west one finds more and more 
numerous fragments of crystalline schists enclosed in this 
— granite, and thus the rock grades, by increase of the enclosed 
— materials, into the migmatites in which the granite occurs 
ers 
as veins and dikes. 
The crystalline schists, forming the older and larger 
