626 



dr. j. a. thomson on the [dec. i9i3, 



Proposed Classifications op 



Classification adopted in this paper. 



Original state of rocks. Present state of rocks. 



Laecombe, 1911. 



Sediments. 



Kurrawang Series (sheared 

 conglomerates, grits, etc.). 



Older sediments. 



Lavas and tuffs (F). 



(a) Fine-grained 

 lites. 



amphibo- 



(b) Fine-grained greenstones 

 and greenstone-scliists. 



(c) ' Calc-schists.' 



Metamorphic tuff. 



Intrusive rocks. 

 A. Peridotites. 



Serpentines, talc-magnesite- j Serpentine, 

 schists, magnesite - rocks, \ 

 fuchsite-magnesite rocks. 



B. Pyroxenites. 



Hornblende-rocks. 



C. Hornblende - 

 dolerites. 



Lustre-mottled amphibolites. 



D. Gabbros or 

 dolerites. 



Epidiorites. 



E. Quartz-gabbros or 

 quartz-dolerites. 



(a) Epidiorites with micro- 

 pegmatite. 



(b) Chloritic rocks with ~") 

 micropegmatite (albitized j I 

 greenstones) and schistose j | 

 representatives. ! C Quartz-andesite. 



— — ' (. Aphanite. 



(c) Bleached greenstones with 

 micropegmatite and quartz- 

 sericite-carbonate-schists. 



F. Porphyrites. 



Porphyrites. 



; Porphyrites (?). 



G. Albite-porphyries. 



Albite-porphjTies. 



-porphyries. 



Mr. H. B. Corbin 1 was the first to doubt the sedimentary origin 

 of the graphitic schists. He showed that certain supposed fossils 

 were only pyritous nodules, arid explained the slaty rocks as due 

 to the contact-alteration of a porphyry by a ' diorite '-dyke. His 

 explanation, however, did not gain acceptance, and for twelve 

 years the views put forward by Prof. Kemp held the field. 



In 1902 the Geological Survey of Western Australia published a 

 map of Kalgoorlie by Mr. A. Gibb Maitland & Mr. W. D. Campbell, 



1 'Notes on the Graphitic Slates & Associated Rocks in the Kalgoorlie 

 District ' [& Discussion thereon] Trans. Roy. Soc. S. Austral, vol. sxii 

 pp. 72-75. 



