SOME GEOLOGICAL FEATURES OF NORTHERN AUSTRALLV. 109 



Quartz is of two ages — an older blue quartz and a later 

 white quartz — -as McLaren has shown for West Australia, in his 

 work on " Gold," and the blue quartz which is sheared, is 

 generally the richer. This blue quartz usually occurs in basic 

 rocks and may be platiniferous. 



McLaren's magnetite-hematite-quartz rocks, considered by 

 him as derived from ferruginous sediments, occur abundantly 

 in the massif, both in Queensland and the Territory, and are 

 here regarded as shear zone formations. Without disputing 

 the possibility of a derivation from sediments, the writer 

 ventures to say that the re-arrangement and crystallisation of 

 the constituents has been aided by movement on the bedding 

 plane and by the introduction of mineralisers along the shear. 



II. THE SOUTH-EASTERN OR KOSCIUSKO MASSIF. 



Victoria, Tasmania and the Monaro district of New South 

 Wales form a geological unit which has been an area of plateau 

 uplift since the cessation of Pernio -Carboniferous folding and 

 mountain-building. Erosion to base level has taken place on 

 several occasions, followed by renewed uplift and more or less 

 faulting. 



Each reduction of the plateau to base level has been 

 followed by marine transgressions, of which the geological 

 record of the Tertiary submergence alone has been preserved 

 to a considerable extent. Thus in North-Eastem Tasmania, 

 Southern and Western Victoria, and in the Riverina district 

 of New South Wales, Kainozoic formations are frequent. 



The faulting accompanying the great Mesozoic uplift 

 was followed by the extension of the great diabasic sheets 

 of Tasmania ; and the Tertiary faulting, which produced 

 Bass Strait, was followed by the basaltic eruptions of Central 

 Victoria. 



The principal alkaline effusions diagnosed in the south- 

 eastern massif were those of Mount Macedon in Victoria, 

 Regatta Point in Tasmania, and the nepheline phonolite dykes 

 of Mount Kosciusko. 



An interesting feature of this massif is the fact that while 

 the general direction of the highlands is east and west, the fold 



