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Reviews—Eruptive Rocks of the Kristiania Region. 5538 
undulose extinction. Fenite also occurs as independent dykes, 
derived by direct meiting (cr solution) of granite in melteigite- 
ijolite magma. These penetrate the melteigite group, and have a 
typical pulaskitic structure. At the border between the fenite and 
melteigite group are quite locally developed the juvites and 
malignites. These are possibly derived from a mixture of fenite 
and ijolite magmas. Their high content of potash is perhaps to be 
explained as a direct transfer of potash solutions from the fenitized 
granite, a process complementary to fenjtization itself. 
Only in the small sack-shaped area in the vicinity of Melteig are 
the rocks of the melteigite-ijolite group completely fresh. Else- 
where they are completely or partially changed to muscovite-hiotite 
(chlorite)-calcite-fels. It is probable that the potash absorbed in 
muscovitization of the already crystallized melteigites is also in 
part derived from the Precambrian granite. 
Whilst the rauhaugite dykes which penetrate the fenite near 
Ringsevja must be regarded as primary, Brégger is of opinion that 
the great eastern mass of rauhaugite is metasomatically derived from 
sovite. The source of the magnesia and iron, if this be so, must be 
the rocks of the melteigite group, from the destruction of pyroxene 
in their conversion to muscovite-chlorite-calcite-fels. Furthermore, 
this metasomatism must have occurred before the intrusion of the 
damkjernites, for these contain in places xenoliths of the typical 
rauhaugite. 
Against this view of Brdeger must be placed the fact that the 
normal rauhaugite does not contain either manganophyllite or 
microlite, The absence of the latter highly insoluble mineral is 
significant, and may point to the rauhaugite as an independent 
intrusion, or, if secondarily changed, a derivative of the magma 
which gave rise to the primary rauhaugite dykes. 
At the conclusion of the fenite formation, and possibly its dyke 
intrusions, the carbonate magma in part retained its fluidity in 
depth, and was then erupted, partly as dykes of sévite, and less 
numerous dykes of rauhaugite, and partly as mixed magmas, as 
ringite, ringite-pegmatite, hollaite-pegmatite, etc. These latter 
pegmatites often show characteristic intergrowths of their con- 
stituent minerals, e.g. calcite and pyroxene. 
Significantly younger than the above rocks and representing the 
last stages in the intrusive sequence are the damkjernite intrusions 
which appear as dykes in the granite, in the fenite, in the melteigite 
group, and in the central carbonatite. Some of the damkjernites 
contain inclusions of these rocks as well as fragments of older 
granite and amphibolite. The damkjernites, as well as the sannaite, 
are late differentiation products of the melteigite group, and show 
a clear relationship with the earliest intrusive vibetoites. Their 
resemblance to the African and Brazilian kimberlites has led to a 
careful search for diamond, but without success. 
As to the epoch of intrusion of the Fen rock series, Brégger was 
