162 ENOGGERA GRANITE AND ALLIED INTRUSIVEt?. 



to those observed in a quartz-porphry which outcrops 

 in the bed of Ithaca creek, and which in most other respects 

 resembles the rhj^olitc rocks. It thus seems to form a 

 connecting Unk between these two very different types of 

 rock. 



A series of intrusions which are very similar to the 

 porphyries have already been described as intruding the 

 granite itself. The porphyries seem then to be younger 

 than the granites, and as they also break through an impor- 

 tant chain of rhyolitic dykes on the southern boundary 

 of Mt. Oootha Reserve, the}^ are younger too than this 

 group of intrusions. 



There are tAvo principal outcrops of the porphj^ry. 

 One is roughly parallel to Taylor Range, and outciops 

 near the top of the ridge which it occasionally crosses, 

 thus probably forming the backbone which has preserved 

 this p;.rt of the range as a residual. The general direction 

 taken l.y this intrusion is thus north-west — south-east. 

 The only other really extensive intrusion of this rock occurs 

 as a series of outcrops about one mile to the west of the 

 Green Hill granite. Here the individual outcrops and the 

 intrusion as a whole seem to strike almost due north, again 

 svniiiathisino: with the long axis of the granites. 



I would like here to exj ress my giatitude to Mr. Rich- 

 ards a]id Mr. Walkom of the Department of Geology in the 

 Uiuversity of Queensland, for the help and advice which 

 they were ever ready to offer me in connection with the 

 preparation of this paper, and their kindly encouragement 

 throughout the whole of the work. 



