Discussion

Abstract

Dr J. V. H epworth said that the Kilonwa syenite occurred in a very interesting tectonic situation, in the boundary zone of the Mozambique Belt at the margin of the 'Tanganyika Shield'. It was an area of high complexity but it was interesting to speculate to which—if any—of the magmatic or metamorphic groups the syenite might bear a relationship. The possibilities were these: immediately to the west lay the Chenene granite batholith known to be over 2000m.y. old; to the north was a charnockitic suite more than 3000 m.y. old and this could be seen to have been intruded and granitized possibly by the Chenene granite; to the south and east was garnet-mica-kyanite-staurolite schist; the whole was overprinted by a more or less penetrative deformation known as the 'Bubu cataclasis' and this was probably associated with the main deformation in the Mozambique belt. Fozzard's map recorded a south-easterly plunging lineation on the Kilonwa syenite characteristic of this deformation which was, judging by the hand specimens and as Dr Kempe had said, strongly deformed. Could Dr Kempe in the first place make any suggestions as to whether the syenite was in any way related to the Chenene granite? Dr Kempe had described the K-feldspar as being a 'string or bleb perthite' with exsolved iron-rich material. This had been taken to be characteristic of leucocratic granulite facies rocks, e.g. Eskola (1952), Hepworth (1964), 1 or at any rate in leucocratic rocks closely associated with granulites, and he wondered if this might suggest