386 



A specimen of the more typical rock from the Giant's Head is even-granular 

 and of aplitic appearance. It is composed of much microline, some orthoclase, 

 and a smaller percentage of albitic plagioclase, together with a little muscovite. 

 Dark-coloured tourmaline is distributed sporadically. 



A second locality visited on the line of this intrusion was Tourmaline Hill, 

 which is half-way between Umberatana Head Station and the Wheel Ellen 

 Mine. Here the rock was seen to be closely related to that of the Giant's 

 Head, but particularly rich in tourmaline. Patches of black tourmaline in quartz 

 and tourmaline in a quartz-felspar rock were noted. In several places there 

 were crystals of a light-green transparent tourmaline. Also large red garnets 

 enclosing poecilitically much quartz and felspar. 



In microscope section the composition of a specimen from this locality is 

 seen to be microcline (probably a soda-microcline), a little orthoclase, notable 

 plagioclase (apparently albite), quartz, a little muscovite and tourmaline. An 

 interesting case was noted of a growth of microcline around a large plagioclase 

 (albite). 



The magma of this intrusion was evidently not at all a normal one, but 

 rather of a pneumatolitic or hydatogenous character. 



Summary. 



1. In the great sedimentary series west of Yudanamutana, glacial tillite*^^^^ of 

 a very definite character with ice-scratched boulders has been met with at Mount 

 Rose, Mueller's Hill, and Red Hill. This feature, taken together with the general 

 lithological character of the beds, fixes their age as Adelaidean, formerly 

 regarded as Lower Cambrian, but recently shown to be more probably Pro- 

 terozoic. Conglomerate and quartzite beds near the base of this series in the 

 Yudanamutana district have the ilmenitic facies distinctive of the basal beds of 

 the Adelaide Series. 



2. Still older rocks, largely igneous in origin and mainly acidic, 

 occupy a belt surrounding Mount Painter, and flanked on either side by the 

 Adelaidean formation. Included are highly metamorphic types which contain 

 elements recalling the Barossian Series of the Mount Lofty Ranges and the 

 Willyama Series of the Barrier Ranges and the Boolcoomatta Hills. In the 

 light of present knowledge, the Mount Painter Belt should therefore be classed 

 with these, and it is to be considered of early or middle Pre-Cambrian age. 

 Certain features noted at Bolla-Bollana Creek and near Willigan Hill suggest 

 that there may be represented two formations older than the Adelaidean beds. 



3. Igneous activity is indicated of either two or three ages. Firstly, an early 

 acid series, including the blue-quartz quart-porphyry shed as boulders in the 

 conglomeratic rock close to Freeling Heights. Secondly, an acid phase, including 

 the pink-coloured quartz-felspar-porphyry intruded into the boulder bed just 

 referred to in the Freeling Heights area ; also the aplitic and pegmatitic intrusion 

 at the Giant's Head. Thirdly, a great basic series intrusive into the Adelaidean 

 rocks in the Yudanamutana district and on the Paralana side of the ranges. It 

 is quite possible that this third series is contemporaneous with the second acid 

 phase. The association of some acid aplite and a quartz-ceratophyre with the 

 basic intrusives of the Mount Remarkable area*^^^^ is further support to this 

 contention. 



These basic intrusives are very similar to those already described "^^^^ by 



(12) First recorded in this area by Professor W. Howchin. 



(13) "Petrographical Notes on the Igneous Rocks of Mount Remarkable," by Dr. E. O. 

 Thiele, Proc. Roy. Soc. S. Austr., xl., 1916, p. 580. 



(14) Proc. Austr. Ass. Adv. Science, xi., 1907, p. 418 ; also Proc. Rov. Soc. S. Austr., 

 xl., 1916, p. 563. 



