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A N:o 1) Igneous Rocks of Sviatoy Noss in Transbaikalia. 
been preserved. It is therefore very difficult to state anything 
with certainty regarding their origin. Probably they are 
various in this respect, just as the gneisses. On the south- 
eastern shore were observed many examples of amphibolite 
as dikes intersecting gneisses etc. Such varieties are almost 
certainly of intrusive origin. The same is probably the case 
with many larger occurrences whose form is not obvious. 
Thesé varieties have the composition of gabbros or diorites. 
Fig. 3. Adergneiss with cross-cutting dikes of aplite. SE-shore 
of Sviatoy Noss. Photo P. Eskola. 
Greater part of the amphibolites, however, is in all probability 
sedimentogenous, or, at least, tuffogeneous. This supposition 
is suggested by the bedded structure and interstratification 
with limmnestones, and by the occurrence of pyroxene-bearing 
layers which may be interpreted as metamorphic derivatives 
of marl or argillaceous limestones, and further by the very 
inconstant composition in their neighbouring layers, part of 
which may consist exclusively of plagioclase and hornblende, 
while others are pyroxene- or quartz-bearing and still others 
also contain almandite. 
