384 



The Western Foothills of Freeling Heights. 



Freeling Heights, a splendid example of an elevated peneplane, stands out 

 to the north-east from Yudanamutana. On the low country near its south- 

 western extremity is the Daley Mine and other copper mines also associated wath 

 areas of basic rock intrusive into the upper sedimentary series. Again there is 

 associated with the sulphides a great deal of micaceous iron. The intruded 

 rocks include a remarkable develpoment of actinolite rock and spotted slates 

 in which tremolite is seen to be forming at scattered centres, crystallizing in 

 radial-fibrous forms. Some of the intrusive rock is slightly vesicular. 



These intrusions at the Daley Mine are into slaty and calcareous beds, 

 which by their relations to a tillite formation further to the north-east are 

 evidently the Flinders Range equivalent of some part of the Adelaide Series. 



At a lower horizon, in the Waterfall Gorge, an extensive and very massive 

 quartzite series is located. This appears to be a continuation of the gorge 

 quartzite of Yudanamutana. Its dip varies a little and it appears to stand 

 conformably upon metamorphosed calcareous sediments passing downwards into 

 more slaty beds, and finally into conglomerate at the base. 



This conglomerate, where examined, was found to be dipping steeply to 

 the S.S.W. The boulders in it, which are rolled out and rendered schistose 

 by pressure, are cemented by a matrix rich in grains of ilmenite and magnetite 

 of original sedimentary origin. Occasionally entire bands of such fine ilmenitic 

 sands traverse the conglomerate. Included blocks of quartz-porphyry are 

 abundant in this conglomerate. A notable feature of this porphyry is that the 

 quartz phenocrysts exhibit a characteristic blue tint. Many of the quartz grains 

 in the matrix of the conglomerate are also of this kind. 



Below the conglomerate are further beds of a slaty and sandy nature, and 

 gravel rock rich in ilmenitic sands and blue quartz particles. 



As a continuation of these beds, at a point somewhat further to the north 

 again, on the flanks of Freeling Heights, is a massive sedimentary formation 

 consisting of quartzites carrying bluish-tinted quartzes and large boulders of 

 quartzite and of quartz-porphyry in which the quartzes show the blue tint. 



An area of massive blue-quartz quartz-porphyry, much schistified, was met 

 with near Willigan Hill. This is evidently a portion of the basement rock upon 

 which the great sedimentary series was laid down. 



All the beds thereabouts are in an advanced stage of dynamometamorphism 

 and, in addition, thermal-metamorphism is evidenced to a considerable degree, 

 often making it very difficult to delineate their original characters. It is, never- 

 theless, quite clear that in the neighbourhood of Freeling Heights there is a great 

 basal series of conglomeratic and quartzitic rocks rich in ilmenite and capping 

 unconformably an older terrain remarkable for the presence of extensive quartz- 

 felspar-porphyry in which the quartzes have a characteristic blue tint. In this 

 latter feature there is a resemblance to the quartzes of the Encounter Bay 

 granite, though the intensity of blue colouration is often greater in the Mount 

 Painter rocks. 



Two different types of igneous rock were noted intruding this great basal 

 sedimentary series near Freeling Heights — one a large basic intrusion, the other 

 a dyke of reddish-brown coloured acid porphyry, macroscopically resembling a 

 type that has been met with in the Flinders Range Tillite at Mueller's Hill. 



A specimen of quarts-felspar-porphyry from the creek one mile north of 

 the Willigan Hill Mine shows rounded, porphyritic bluish quartzes and the 

 outlines of porphyritic felspars embedded in an aphanitic grey base. The micro- 

 scope slide reveals that the quartzes are corroded and show pressure cracks and 

 undulatory strain extinctions. The relics of porphyritic felspars appear in 

 3-gg^egates of secondary minerals. Relic structures in some of the felspars suggest 



