﻿Vol. 66.] GEOLOGICAL STRUCTURE OF SOUTHERN RHODESIA. 355 



features of the greater part of the metamorphic areas. They can 

 only be called 'schists' by convention, as they rarely show any 

 signs of foliation ; and one is strongly tempted to abandon the 

 term ' dynamic ' as applied to the type of metamorphism which 

 they exhibit. ' Static ' would seem a more appropriate term, and 

 there is certainly no evidence of any intense differential movement 

 during the evolution of the processes which imparted to most of 

 the Rhodesian rocks their present characters. 



Among the hornblendic rocks under consideration, and certain 

 other types associated with them, there are probably two distinct 

 classes. It may be surmised that some of them are representatives 

 of the ' Basement Schists,' upon which the altered sediments, 

 presently to be described, were originally laid down. On the other 

 hand, many, indeed most of them, are probably among the youngest 

 members of the metamorphic series, evidently representing igneous 

 intrusions of various types, chiefly basic. Some retain very per- 

 fectly an original ophitic structure, despite uralitization, etc. (for 

 instance, Rifle Kopje, near Bulawayo ; Red Hills, Victoria district). 

 In other cases they occur as well-marked dykes among the altered 

 sediments, as, for example, in the Conglomerate Series in the bed 

 of the Hunyani River at Lomagundi. Where this is not the case 

 there is only analogy of structure to go upon. It is worth noting 

 that, as they are altered intrusions, and therefore came up from 

 below, they may simulate any age prior to their real one. They 

 do, in fact, often exhibit a relation to the other rocks which would 

 lead to their classification as older than those if their intrusive 

 character were not realized. Although of different ages, all these 

 rocks are clearly older than the great granite masses, by which, 

 indeed, the whole of the members of the metamorphic series are 

 alike invaded. 



(2) The < Banded Ironstones.' 



Perhaps the most striking and anomalous to the European eye 

 are the rocks locally known as * Banded Ironstones/ a term which 

 may lack precision, but is so well understood that it would be a 

 pity to eliminate it from scientific literature. These rocks are 

 well developed south-east of Bulawayo, where they verge upon the 

 town ; but their most conspicuous development is along the eastern 

 border of the province of Matabeleland, from Gwelo to the Umniati 

 River. Each separate exposure may be either only a few or 

 many hundred feet thick ; but in numerous cases the intercalated 

 beds must be regarded as also belonging to the same general series. 

 The southern equivalents or analogues of the Banded Ironstones 

 have been variously referred to as ' magnetic quartzites,' ' banded 

 jaspers,' ' haematite-schists/ 'striped cherts,' 'calico rock,' etc., 

 and these names will serve as an indication of their lithological 

 characters. Although by no means uniform, they must unques- 

 tionably represent a series consisting largely of fine mechanical 

 sediments. Their conspicuous banding may be attributed chiefly 



