GEOLOGY 37 



a heterogeneous magma. Various interbedded amphibolites 

 are believed to represent earlier consolidated basic igneous 

 rocks which have become involved in the later granite-gneisses. 

 It is shown that this South Australian Pre-Cambrian tract has 

 a striking resemblance to the Laurentian region of North 

 America, particularly to the Haliburton-Bancroft area of 

 Ontario. 



A further paper deals with the dolomites and calc-magnesian- 

 silicate rocks of the Hutchison Series, the oldest sedimentary- 

 rocks of the Eyre Peninsula {Geol. Mag., 1920, 67, 449-62 ; 

 492-500). These rocks have been invaded by the above- 

 mentioned granite-gneisses. In the dolomites residuary 

 crystallisation alone can account for the development of the 

 metamorphic minerals ; but for certain diopside-bearing rocks 

 it is considered that there has been an additive metamorphism 

 superposed on to the normal residuary crystallisation, due to 

 the influx of silica-bearing solutions from the invading granites. 

 The graphitic schists and gneisses which also occur in the 

 Hutchison Series are described in another memoir (Econ. Geol., 

 1 92 1, 16, 184-98). They are associated with the dolomites 

 described above, and w4th para-garnet-gneisses. The graphite 

 is ascribed to a sedimentary origin, the original rocks being 

 regarded as bituminous shales, arkoses, and sandstones, in 

 which carbonisation of the bituminous matter and recrystallisa- 

 tion of the carbon to graphite have accompanied strong meta- 

 morphism. The development of graphite along joints in some 

 cases is possibly due to reduction of oxides of carbon by hydrogen 

 — the carbon being supplied from carbon dioxide released 

 during the silication of the accompanying limestones. 



The metamorphic rocks of the basement series of South 

 Victoria land are described in two recent memoirs (" The Meta- 

 morphic Rocks of South Victoria Land," 5a, W. C. Smith and 

 F. Debenham ; "The Metamorphic Rocks of the McMurdo 

 Sound Region," 53, W. C. Smith and R. E. Priestley, " The 

 Metamorphic Rocks of the Terra Nova Bay Region," British 

 Antarctic (** Terra Nova ") Expedition, 19 10, Geology, vol. i, 

 No. 5, 1 92 1, 131-66). In the McMurdo Sound region they 

 comprise a considerable thickness of schists and crystalline 

 limestones probabty with pyroxene-granulites, and represent 

 metamorphosed argillaceous, calcareous, and dolomitic sedi- 

 ments. There is also an intrusion of biotite-hornblende- 

 gneiss, and some hornblende-schists representing altered d3'ke 

 rocks. The assemblage is remarkably similar in all characters 

 to that described by Mr. Tille}" from the Eyre Peninsula of 

 South Australia (see above). 



The Terra Nova Bay region is generally similar. A porph}- 

 ritic biotite-gneiss of igneous origin occurs in situ. The moraines 



