62 THE KRAAIPAN FORMATION 



openings, hence the proportion of magnetic quartzite 

 and chert is apt to be overestimated. 



The thickness of this formation here, even at the very 

 lowest estimate, cannot be less than 10,000 feet, while 

 the highest beds visible are faulted against the granite. 



At Madibi the rocks are thinner bedded and consist 

 of alternations of magnetic quartzite and sericite-, chlo- 

 rite-, and calcareous-schist. 



At Pitsani and Mosita the proportion of volcanic 

 material increases, and the magnetic quartzites and 

 cherts form thick bands alternating with great thick- 

 nesses of diabasic lava and sometimes diabase breccias 

 and tuffs, quartz-porphyries, grits and slates. 



Where the Setlagoli Eiver cuts through the western 

 belt there are four great zones of diabase and the inter- 

 bedded sedimentaries prove to be representatives of 

 those seen in the central belt ; the lowest is composed 

 of magnetic quartzites, the second of chert and jasper, 

 and the third is a series of cherts and quartzites. A 

 thick zone of diabase accompanied by some quartz- 

 porphyry intervenes between the lowest magnetic quart- 

 zite and the granite ; this is w T ell seen both at Pitsani 

 and Mosita. 



At the last-named locality the junction of the diabase 

 and granite is clearly exposed and there is no evidence 

 of the latter rock being intrusive. The thickness of the 

 formation just north of Mosita cannot be less than 10,000 

 feet, of which fully two-thirds must be of volcanic origin. 



The strata appear to have been subjected to more in- 

 tense metamorphism towards the south-east, and the 

 chloritic and hornblendic schists in that area are evi- 



