BY H. I. JENSEN, D.SC. 187 



To the Carboniferous belong the Tasmanian ore 

 deposits ; the Victorian goldfields ; the Yalwal, Braidwood, 

 and other southern goldfields of N.S.W.; the Moruya, 

 Ettrema and Colerado mineral fields of the south coast 

 of N.S.W.; the Grafton Copper Mine (?), Cloncurry, Chil- 

 lagoe, the Etheridge, Hodgkinson, Palmer and " Towers " 

 fields. 



To the early Mesozoic period belong the ore deposits 

 of Gympie, Q., and most of the New England deposits. 



The deep leads of Eastern Australia show us that 

 it was not until the early Tertiary uplifts that the con- 

 tinent was sufficiently dissected for the reefs to shed their 

 gold on the surface. 



In Western Australia, the igneous injections giving 

 rise to ore bodies were of very early Palseozoic age. Con- 

 sequently there are sedimentary rocks as old as Cambrian 

 in W.A. with alluvial gold. The silver lead deposits of 

 Broken Hill also belong to an earlier era than those of 

 Eastern Australia. 



Certain facts in connection with ore deposits in 

 Australia are of interest without being quite apropos in 

 this paper, such as : 



1. The association of complex ore (lead, zinc, copper, 

 silver, arsenic) with limestone as at Mungana, Q., Ettrema, 

 &c., N.S.W., and with garnet rock (metamorphosed 

 limestone), at Broken Hill. 



2. The possibility that Gympie gold is due to chemical 

 precipitation of gold in magmatic water, by the carbon- 

 aceous Phoenix slates and graphite beds ; that Chillagoe 

 is a contact deposit ; that the Towers gold is probably 

 due to physical changes undergone by magmatic waters, &c. 



Brief Review of the Tertiary. 



E. C. Andrews in his '' Tertiary History of New Eng- 

 land," and in the '' Geographical Unity of Eastern Australia," 

 has given a very detailed and complete history of the 

 Tertiary, and full description of the processes whereby 

 land and sea forms were shaped. No complete description 

 will, therefore, be essayed here. 



It is sufficient to say that most Australian geologists 

 are converging to the belief that there are definitely two 

 Tertiary peneplains represented in our scenery. 



