46 



BASIC AND ULTRABASIC IGNEOUS ROCKS— BENSON. 



[Memoibs National 

 I Vol. XIX, 



detailed study shows that it cuts successively across the different members of the Pretoria 

 series, breaking some up into detached fragments and following others for some distance. In 

 places it even comes into contact with the old granite (Kynaston '08, Humphrey '10). The 

 contact-metamorphism produced by this intrusion is very great and indicative of high pressure, 

 which is more marked in the east than in the western region, where the laccolite was compara- 

 tively shallow (Hall '09, Humphrey '10). There is also a marked schistosity in the norite, 

 and more basic rocks throughout the whole marginal zone of the complex, which is of the nature 



Fig. 14.— The Bushveld complex. (After MolengraaS and others.) 



1. Pre-Cape complex. 



2. Black Reef series. 



3. Great Dolomite. 



4. Pretoria series. 



5. Pyroxenite and norite. 



6. Red granite. 



7. Waterberg series. 



8. Nepheline syenite. 



9. Karroo sediments. 

 10. Amygdaloidal lava. 



of primary gneissic structure, for no sign of crushing appears in the rock itself. The differences 

 in composition of the successive bands so produced are such as to cause occasionally a regular 

 cuesta- topography, the dip of the bands being precisely parallel with that of the adjacent Pre- 

 toria series (Hall '09). The norite is closely associated with pyroxenite, the one passing into 

 the other without sharp separation, and sharing the same general foliation, while also bands 

 of peridotite may appear (Humphrey '11, Kynaston '11). On the other hand the norite may 



