FE NE Sk 2 a 1 NOEN LEN GER SN SNES 
SN 
34 Pentti Eskola. (LÄTT 
mass: the number and quantity of the melanocratic dikes 
is quite trifling as compared with the aplites. No less difficult = 
to explain is also the frequent recurrence of the lampro- 
phyric and -aplitic intrusions observed in so many places. 
The composition of the lamprophyres appears to be variable = 
and not conformable to the typical dike-rock families. = 
The dike-rocks on Sviatoy Noss thus offer many inet 
teresting features, but the observation does not give any — 
positive evidence, as to the mode of origin of the diaschistie - 
rocks. Further discussion therefore seems unnecessary, until 
more knowledge about the physico-chemical Progesren At 
such differentiation. is arrived at. SS 
The pegmatite. 
Common pegmatite and its contact- 
products. 
Common pegmatites are called all such pegmatites 
which have microcline-perthite, quartz and mica as their 
main constituents. Such pegmatites are found in every part 
of Sviatoy Noss and penetrating all the other kinds of rocks. 
In the fine-grained aplite-like granite forming a zone 
around the great granite mass the pegmatites often EN å 
a zonal structure, elongated crystals of feldspar protruding - 
from the salbands in a parallel Hg towards the : a 
central parts. är 
Pegmatitic Scertod td or NV veins s similar to those 
and larger masses of aplitic granites invading the schistone oc 
rock and also in such masses which are themselves dike- 
formed. The pegmatites intruded in the coarse-grained = 
granitic rocks are more independent in their occurrence than Ey 
those in the aplitic granites and generally have sharp boun- = 
daries. The central zone of the dikes often is made up of 
quartz. 'Orthite in the form of minute crystals of the typical 
shape is fairly common, though never : Tönne in any Targa 5 
quantities. i | 
"Ry RER 
; SÅ 
