90 



MR. C. E. TILLET ON THE GRANITE- GNEISSES [vol. Ixxvii, 



coarse hornblendic va^iet3^ The amphibole occurs here in ciystals 

 exceeding in size those found elsewhere in the Flinders Series. 

 Quite commonl}^, crystals 3 inches long are present, and in one 

 case a single crj'stal, 8 inches long and 1| inches in diameter, 

 was noted. The relations of these pegmatites to the basic 

 amphibolite inclusions are similar to those already described for 

 the Lincoln area. 



Pegmatites carrying large crj^stals of pink garnet are also not 

 micommon, the felspathic constituents being both microcline and 

 acid plagioclase, the former predominating. These often show a 

 distinct gneissic banding, and with a finer granulation the}^ pass 

 into aplite-gneisses. 



Fig. 5. — Sanded gneiss, Hed Banlcs, 



[wa=aplitic gneiss ; gn=gTey gneiss ; rp=red pegmatite.] 



The granites which form sill-like masses in the metamorphosed 

 sediments of Sleaford Bay are hornblendic types, and do not carry 

 garnet. Their felspars are again microcline and plagioclase, the 

 latter being usually more acid in composition than the plagioclase 

 of the main granite-gneisses of this region. The comjDosition of 

 their plagioclase is, however, never more acid than that cha- 

 racteristic of an oligoclase-albite. 



The foliation of the Sleaford gneisses presents the same features 

 as those expressed in the gneisses of the Lincoln area, bnt they 

 are here developed on a more extended scale, Avith additional 

 peculiarities. This foliation has a general southward direction, 

 with the planes steeply inclined. The additional feature to be 

 remarked is the frequent presence of a marked banding. The 



