COMMISSION GEOLOGIOUE - Arkisto.gsf.fi

66 Bulletin de la Commission geologique de Finlande N: 0 212.
0.. t
~ Q
Atso Vormo 1963
Rapakivi granites
Porphyritic gronodiorite
Granodiorite
Potash granite
Gabbro. diorite. infracrustol amphibolite
Suprocrustal rocks
Fig. 8. Location of sampIes investigated within map sheet 3134 (Fig. 1, area II).
SOUTHEAST FINLAND
Granodiorite with its porphyroblastic varieties forms many small massifs
in the area of map sheet 3134 (Fig. 8). Mostly the gray ground mass of the
rock is slightly foliated and medium-grained. Potash feldspar insets vary
from 0.5 cm to 5 cm (or even to 7 cm) in diameter. In places they are very
far apart, in places side by side. Between these two types there occur all
the varieties in between. The most common is the variety where insets of
2-5 cm in diameter are at distances of 2-4 cm from each other (Fig. 9).
The insets are usually angular, in more basic varieties often also ovoidal
in shape.
The gabbros and diorites of the area are regularly older than the granodiorites:
occasionally, however, a gradual transition between diorites and
granodiorites is seen. The transition from even-grained to porphyroblastic