214 AUSTKALASIAN ANTARCTIC EXPEDITION. 



PLATE VIII. 



Fig. 1. Garnet amphibolite, No. 953, Stillwell Island. The large garnet is pene- 

 trated by an area of vermicular pyroxene and felspar. It appears as if a portion of the 

 garnet crystal has broken up into the pyroxene and felspar, but this is not the general 

 case. Mag. 35 diam. 



Fig. 2. Garnet amphibolite, No. 953, Stillwell Island. The pyroxene vermiculse 

 are set radially to an ilmenite nucleus and are partially enclosed by the garnet. The 

 crystals of ilmenite have been set in secondary pyroxene which has partly reacted with 

 the felspar to produce garnet while the residue now appears as vermiculse. Mag. 35 diam. 



Fig. 3. Garnet amphibolite, No. 953, Stillwell Island. The same phenomena as in 

 Fig. 2 appears enclosed within a garnet crystal, but it has the same origin. This example 

 only differs from Fig. 1 in the presence of the ilmenite, and hence it is not necessary 

 to assume the decomposition of the garnet in Fig. 1 . The large garnets are due to growth 

 at the expense of the smaller garnet crystals, and, like all crystals in recrystallised rocks, 

 may include all other constituents. The fact of inclusion has little significance. Mag. 

 35 diam. 



Fig. 4. Garnet plagioclase pyroxene gneiss, No. 935, Stillwell Island. The centre 

 of the field is occupied by a granulitic mass of secondary pyroxene, and this is surrounded 

 by a garnet rim, produced by the interaction between pyroxene and felspar. Mag. 35 

 diam. 



Fig. 5. Another field in the same slide as Fig. 4. The nucleus of granular pyroxene 

 is much smaller. Mag. 35 diam. 



Fig. 6. Almost the same field as in Fig. 5 in polarised light. The garnet is black 

 and the granulitic character of the pyroxene is noticeable. The manner of the change 

 in the composition of the felspar, concurrent with the formation of the garnet, is seen. 

 The outer rim of the felspar crystal, together with the " graphic " inclusions, have a 

 smaller angle of extinction than the bulk of the crystal. Mag. 45 diam. 



PLATE IX. 



Figs. 1, 2, and 3. These are different examples of the composite type of meta- 

 morphosed xenoliths composed of saussurite and hornblende, from Cape Denison. The 

 saussurite marks the junction with the enclosing amphibolite. Fig. 2 shows a remark- 

 ably angular xenolith. The crystal boundaries of the primary felspar in the primary 

 aggregate can be distinguished in Fig. 3. The specimens in Figs. 2 and 3 were not found 

 in situ though very close to the actual outcrop of the xenoliths. Similar specimens 

 were found in situ and are in the collection, but the pebbles make excellent diagrams. 



Fig. 4. This is also a diagrammatic specimen, obtained from the " lower moraine," 

 at Cape Denison, close to the in situ occurrence. It is an amphibolite dotted with pieces 

 of saussurite of varying sizes. 



