FIELD OBSERVATIONS IN NORTHERN NORWAY 705 
proved not to be the case. The norite body forms a lens in its 
normal position between the schists, with a mean dip of about 
30°, and the basic border zone is quite as well developed in the 
upper as in the lower part of the lens. 
Between the quartz-norite and the normal norite there is no 
eruptive contact, but a gradual though rapid transition. 
As a third group we may unite all the olivine-bearing rocks: 
lherzolites, troctolites, and olivine-norites, generally very rich in 
olivine and sometimes nearly of dunitic composition. ‘They occur 
as very numerous, greater or smaller bosses and bands in the normal 
olivine-free norite of the marginal zone, but never in the central 
quartz-norite. 
In the marginal zone they occur irregularly distributed all 
through it from the outer contact with the schists toward the inner 
border against the quartz-norite and all around it, quite as nu- 
merous in the upper as in the lower part of the eruptive. They 
strike one as being swimming bodies in the norite magma. It is 
easily proved that they are neither younger intrusions nor older 
inclusions, but are very nearly of the same age as the environing 
norite. 
While the above-named groups of rocks are all very nearly 
related and form a stepwise but nearly continuous series without 
definite eruptive contacts, there is chemically and tectonically a 
gap between these and a last group of eruptive rocks. The latter 
form well-defined dikes, cutting all the former rocks and consisting 
of an aplitic soda-rich granite. ‘That they belong to the same 
eruptive series, with their source in the central part of the lens, is 
proved by the fact that they are confined to the norite field and 
occur in greatest quantity in the central field of quartz-norite. 
Here they form a network of narrow dikes, occupying about 7 per 
cent of the total area. The dikes are well defined, but with slightly 
blurred contacts. The same dikes occur also in the marginal 
norite, here only occupying about 3 per cent of the area, but more 
regularly and with razor-sharp contacts. 
The very last products of volcanic action are some irregular 
veins of pegmatitic potash-granite and of snow-white, pure quariz, 
both carrying black tourmaline. 
