78 
oblique angle. The red zone thins out towards the west-south- 
west and disappears a little to the west of the place where it 
cuts across the brook at a height of about 230 meters. Fol- 
lowing it from here upwards the zone gradually becomes 
broader; at a height of 420 meters it is almost 100 meters 
broad, but further to the E. N.E. the alteration is less intense 
and there is a gradual transition to the unaltered rock. It is 
evident from the mode of occurrence that the transformation 
has proceeded from a vertical fissure; through this there was 
first an emanation of gases containing fluorine and iron, 
which saturated the rock with fluorite and hematite; later, 
with decreasing temperature, water vapour and hot water have 
IWS 
Fig. 13. North Siorarsuit, seen from the west. 
S, gravel plain of N. Siorarsuit; N, Nunarsuatsiak; f, sodalite-foyaite; n, naujaite and 
lujavrite; xx, zone of red-coloured naujaite and lujavrite; d, diabase. 
found a way through the fissure and led to the formation of 
zeolites. 
The mountain slopes west of N. Siorarsuit. — At the foot 
of the mountain west of the gravel-plain the naujaite is ex- 
posed. At an altitude of about 140 meters this is overlain by 
the sodalite-foyaite, in quite the same manner as south of the 
fjord (р. 68). The sodalite-foyaite is cut by a considerable 
number of tinguaitic dykes, which are dark-green or bluish 
green and of a dense structure, but have only a slight breadth. 
The largest tinguaite dyke observed here was 70 centimeters 
broad. Between the naujaite and the sodalite-foyaite there is a 
gradual transition. The transitional zone is not quite hori- 
zontal, but rises from N. Siorarsuit both towards the north and 
