190 PROCEEDINGS OF SECTION C. 



amphibolites and less altered uralitised dolerites and basalts. The 

 latter were observed to be amygdaloidal at an outcrop on the 

 Arkaroola Creek, near the quartzite to which reference has been 

 made. About one mile south-west of Mt. Painter there is an 

 extensive outcrop of very coarse amphibohte in which huge crystals 

 of clove brown sphene are abundantly scattered ; individual 

 crystals have been got several pounds in weight. 



Undoubtedly the neighbourhood of Mt. Painter has, in pre- 

 Cambrian times, been the scene of great igneous activity, both 

 acid and basic effusive and plutonic types of that age are there 

 represented. There has been, also, post-volcanic activity to a 

 marked degree. This is evidenced, firstly, by pneumatolite 

 metamorphism producing the micaceous corundum and spinel- 

 bearing belts above noted ; secondly, by ore and quartz reefs such 

 as result from geyser action ; these latter occur on a truly magni- 

 ficent scale. The most notable of these extends through Mt. 

 Painter itself, its great hardness determining the relief. This reef 

 is specially notable on account of the uranium ores which it 

 contains. 



Flanking these pre-Cambrian highlands are undulating plains 

 and hills composed of Cambrian sediments. On the north-west 

 side the basal beds are well exposed between the Daly mine and 

 Freeling Heights. Coarse boulder conglomerates are here con- 

 spicuous. Amongst the boulders are fragments of the quartz 

 porphyry occurring massive in the adjacent pre-Cambrian series. 

 As usual elsewhere, also, ilmenite and magnetite grains are abund- 

 ant amongst the finer material. Above are grits, slatey, and cal- 

 careous beds. An immense thickness of these is exposed in the 

 Flinders Range, to the west, as already shown by Mr. W. Hcwchin.i 

 The Cambrian glacial till horizon outcrops at intervals to the 

 west, for instance, at " The Red Hill," near the Wheal Turner 

 Mine, at Muller's Hill, and in the vicinity of the Mt. Rose Copper 

 Mine. At Muller's Hill I picked up seven distinctly glaciated 

 pebbles in a few minutes. 



Ml. W. Howchin^ has already drawn attention to intrusions 

 of a basic magma in the Cambrian strata of the Flinders Range, 

 Large intrusions of this nature are met with at Yudnamutana and 

 at the Daly and Stanley Mines. These are genetically connected 

 with workable copper deposits. 



Intrusions of normal granite into the Cambrian sediments 

 have not been observed, though a great dyke-like tongue of an 

 acid character, situated two miles south of Umberatina, extends 

 east and west for several miles. This has resulted from the 

 crystallisation of a magma highly charged with gaseous products. 

 This deduction is evidenced partly by the porosity of the rock. 



1 Proc. A.A.A.S., Adelaide, 1907. 



2 Loc. cit. 



