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VOLCANIC ROCKS 01' MOZAMBIQUE. 



261 



Museum), and it is clear that in no essential respect do they differ 

 from the Mozambique examples ; even the arnygdale minerals and 

 the order of their deposition are the same. 



South of the Zambesi, basalts, largely -amygdaloidal, are found 

 associated with late Karoo sediments, flanking the plateau of 

 crystalline rocks for hundreds of miles. In tbe north they have 

 been mapped by Dr. E. 0. Teale & Mr. R. C. Wilson. 1 Between 

 the Pungwe and the Sabi (Save) rivers they were traced by 

 Col. A. Freire d'Andrade. 3 Some 50 miles west of the mouth of 

 the Busi, he collected melaphyres in which chlorite-lined amygdales 

 containing zeolites and chalcedony" and quartz are abundant. 

 Similar flows of melaphyre occur in Lourenco Marques. I have 

 examined specimens from the Komati River that appeared to be 

 identical with the basalt of the Sokoto sill. The Lebombo 

 amygdaloids of Swaziland and Zululand are associated with 

 andesites and rlryolites, and some of these have been analysed. 3 



Occurring farther from the coast, the Drakensbergen lavas, 4 

 the Bushveldt amygdaloid of the Transvaal, 5 the Tuli lavas of 

 Southern Rhodesia, 6 the Batoka basalts of the Zambesi, 7 the 

 basalts of the Forest Vale between Bulawayo and the Zambesi, 8 

 and the Ngami amygdaloids of tbe Kalahari, 9 all show a marked 

 likeness one to the other and to the Mozambique lavas. Towards 

 the south the resemblances become less marked, though the differ- 

 ences are limited to the incoming of olivine (generally serpen - 

 tinized) among the pyrogenetic constituents, and of calcite among 

 the arnygdale minerals. 10 Throughout this vast region, west and 

 south-west of Mozambique, no alkali series of rocks is known to 

 occur in association with the late Karoo amygdaloids (except 

 doubtfully those of the Bushveldt complex, where the age of the 

 intrusions that preceded the amygdaloids is still uncertain). It 

 seems, however, worthy of remark that the igneous rocks that 

 followed the Upper Karoo amygdaloids and the later dolerites of 

 South Africa are generally melilite-basalt, alnoite, or kimberlite. 

 These rocks occur in the Cape Province, the Orange Free State, the 

 Transvaal, Southern Rhodesia, Northern Rhodesia, and Katanga. 



1 Geogr. Journ. vol. xlv (1915) p. 29. 



2 P. Choffat, ' Contributions a la Connaissance Geologique des Colonies 

 Portugaises d'Afrique ' Comm. Geol. Portugal, ii (1905) p. 33. 



3 J. McC. Henderson, Trans. Geol. Soc. S. Africa, vol. xii (1910) p. 24. 



4 A. W. Rogers & A. L. Du Toit, ' The Geology of Cape Colony ' 1909, 

 p. 225. 



b E. T. Mellor, Ann. Rep. Geol. Surv. Transvaal, 1901, p. 31. 

 G A. J. C. Molyneux, Q. J. G. S. vol. lix (1903) p. 266. 



7 G. W. Lamplugh, ibid. vol. lxiii (1907) p. 162. 



8 P. P. Mennell, ibid. vol. lxvi (1910) p. 369 ; and Spec. Pep. % Rhodesia 

 Museum, 1904, p. 15. 



3 S. Passarg-e, Zeitschr. Gesellsch. fur Erdkunde, Berlin (1904) no. 3, 

 p. 179. 



10 A. W. Rogers & A. L. Du Toit, ' The Geology of Cape Colony ' 1909, 

 p. 226 ; see also P. A. Wagner, ' The Diamond-Fields of South Africa ' 1914, 

 p. 99. 



Q. J. G. S. No. 287. u 



