FIELD OBSERVATIONS IN NORTHERN NORWAY 707 
The distinct gap between the main mass of massive norites and 
the dike-formed acid differentiation products of aplitic granite 
reminds us very much of corres- 
a ponding features of the “red rock” 
Sora in the Duluth gabbro.t 
YY The deposits of nickeliferous 
V// pyrrhotite—which will not be 
treated here—are in their occur- 
rence confined to the olivine- 
bearing rocks and to the marginal 
normal norite, and no traces of 
them are found in the quartz- 
norite or the younger dikes. In 
the olivine rocks the sulphides 
occur only as impregnations, but 
are relatively very rich in nickel. 
While the percentage of sulphur 
generally is between 1 and 2 per 
cent, the nickel content neverthe- 
less reaches 0.7 per cent, of which 
not more than o.1 per cent seems 
to be in the form of silicate in the 
olivine mineral. In the norite, the 
sulphides occur partly as impreg- 
nations, partly as segregated richer 
masses, but the nickel content in 
the pure sulphide is lower, gener- 
ally between 1.5 and 4 per cent. 
The mineralogical composition of 
the rocks is as follows: 
The olivine-bearing rocks consist 
/ of olivine, rhombic and monoclinic 
3 Vj pyroxene, and plagioclase, but gen- 
3 —} erally no primary biotite. Acces- 
sory constituents are picotite, green spinel, magnetite, and pyr- 
rhotite. The rhombic pyroxene is an enstatite with less than 
500 
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Raaneggen 
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Fic. 2.—Section through the Raana field. Vertical and horizontal scale, 1:100,000 
SS 
S 
S 
t Frank F. Grout, “A Type of Igneous Differentiation,” Jour. Geol., Vol. XXVI, 
pp. 626 ff. 
