part 1] THE PRE-CAMBRIAN ROCKS OF MOZAMBIQUE. 37 



II. Succession and Classification of the Rocks. 



(a) The Coastal Districts. 



The Archaean succession in Mozambique, so far as it is developed, 

 bears a close resemblance to that of other African localities, and 

 many of its features are similar to those of the Archaean areas of 

 India, Ceylon, Fennoscandia, and Canada. Representatives of the 

 oldest rocks of the territory are found underlying part of the 

 •coastal belt between Mitikiti and Ibrahimo. They consist of a 

 series of micaceous quartz-schists and paragneisses interfoliated 

 with granite-gneisses that appear to have been injected between 

 successive bands of an older sedimentary formation. No original 

 basement on which the schists could have been laid down as 

 sediments can be found. Granulitic granites and pegmatites, 

 predominantly grey or nearly white, traverse the schists and 

 gneisses ; and a later red granite, accompanied by coarse-grained 

 pegmatites free from any trace of granulitic structure, cuts through 

 all the members of the older complex. 



A similar succession is observed south of the Lurio, between 

 Nunua, 12 miles from the coast, and Fort Naparara. Here are 

 numerous bands of crystalline limestone interfoliated with the 

 gneisses, and accompanied by thin belts of haematite- schist. As 

 the crystalline limestones are approached, the normal biotite- 

 gneiss gradually changes to hornblende-gneiss and amphibolite, 

 and much plagioclase appears in place of the usual alkali-felspars. 

 Mica-schists have not been recorded from this district, nor indeed 

 from any part of Mozambique other than that mentioned above. 

 Graphite ores associated with quartz- veins are said to occur near 

 Nunua, but nothing is known of their mode of origin or position 

 in the sequence. At Niveta, and in the hills west of Naparara, 

 there are small intrusions of a grey granulitic granite which is 

 sometimes porphyritic. Red felspathic pegmatites .of later age 

 have been traced near Niveta, into quartz- veins which carry con- 

 siderable quantities of galena. 



West of Memba crystalline limestones and hornblende-schists 

 are interfoliated with the gneisses, which in many places are highly 

 garnetiferous. Thus it happens that deep-red garnets, often an 

 inch in diameter, are thickly sprinkled among the gravels of the 

 Mukuburi River. Due north of Memba a heavy dark-green 

 eclogite is interbanded with the garnet-gneisses of the Muendazi 

 Valley. Tourmaline-granites and pegmatites belonging to the 

 coarse-grained later type are strongly developed around Memba, 

 and in the town itself the post-otHce is built on an outcrop of 

 quartz-tourmaline rock. For allowing me to make use of his 

 notes on the Memba district, I am indebted to my former col- 

 league, Mr. D. Alexander Wray. 



