506 C. B. Eorwood 8f A. Wade— The Old Granites of Africa. 



Mashonaland and Matabeleland, show that the bulk of the country 

 consists of granite, and the remainder chiefly of nietamoiiihic rocks, 

 chiefly chlorite- and hornblende-schists, epidiorites, actinolite rocks, 

 diabases, dolerites, and other igneous rocks. It is their opinion that 

 the schists are, at all events for the most part, derived from basic 

 igneous rocks which have invaded the granite, and do not represent 

 ancient sediments deposited on a granite floor. They consider the 

 granite and schists constitute a portion of that ancient floor of 

 granite and metamorphic rocks that elsewhere underlie the subsequent 

 sedimentaiy or igneous accumulations. 



As illustrating the widespread distribution of Old Granites and 

 Gneiss in Southern Africa, Mr, J. Kuntz,' speaking of Little 

 jS^amaqualand, says: "Like everywhere else in South Africa, the 

 base of all stratified rocks is formed by granite and gneiss with its 

 varieties and developments into the old crystalline schists." 



"With reference to the southern part of Great IS'amaqualand he 

 states that towards the north the Archaean rocks become more covered 

 by younger strata, and the zone of granite-gneiss is confined to 

 a narrower strip along the coast ; and also that in the northern 

 part of Great Naraaqualand almost the whole country consists of old 

 schists, varying from the gneiss to mica-schists, amphibolite-schists, 

 quartzites, and chlorite-schists. He says that in the granite zone of 

 the Swakop River, situated to the north and north-west of the 

 schistose zone of the Kuisib Valley, the granite is intrusive in 

 the old schists, but only near the basal granite- gneiss, in which the 

 granite is also intrusive. He remarks that it appears as if formerly, 

 when the crust of the earth was very thin, the folding movement, 

 such as that which tilted up the old schists, caused outbreaks of the 

 underlying granitic magma. 



Dr. r. "W. Voit,^ in describing the geology of German South- West 

 Africa, divides the whole country into a gneiss and schist zone and 

 a gneiss-granite zone, pointing out that there are intrusive masses of 

 granite, especially frequent in the western half of the country, 

 containing large fragments of gneiss and schist, which undoubtedly 

 belong to the gneiss and schist zone. In the gneiss-granite area 

 there is a strong predominance of granite. He points out that certain 

 coarse-veined gneiss is merely a structural variety of the granite, 

 and also that a special feature of the district is the occurrence of 

 crystalline limestones, some of which are interbedded in the schists, 

 and which he regards as true members of the schist formation. 



"With regard to the gneiss-schist area, he remarks that the gneisses 

 and mica-schists appear to be connected with each other by almost 

 imperceptible gradations, and that, moreover, a certain sequence is 

 apparent, which he illustrates by an ideal cross-section from Jakalswater 

 to Gansberg, a distance of about 85 miles, in which from below 

 upwards we have — 



1 " Copper Ore in South-West Africa," by J. Kuntz : Trans. Geol. Soc. S.A., 

 1904, vol. vii, pt. ii, p. 70. 



^ " A Contribution to the Geology of German South-West Africa," by Dr. F. AV. 

 Voit: Trans. Geol. Soc. S.A., 1904, vol. vii, pt. ii, pp. 77-94. 



