152 ENOGGERA GRANITE AND ALLIED INTRUSIVES. 



described 1)V Leo. A. Cotton.^ .Such an intrusive mass 

 is to be seen on the summit of Mt. Enoggera, which is the 

 highest }3oint in the area. This particular occurrence 

 appears to grade into a biscuit-coloured fine grained rock, 

 containing a noticeable amount of biotite. This phase is 

 interesting since in it the writer has discovered flakes of 

 molybdenite arranged along the joint planes. Other 

 rocks which should be mentioned here are the typical greisen, 

 which occurs near the Enoggera Reservoir, and in Portion 

 856, Parish of Enoggera 



Considered both as a whole and in detail, this aplitic 

 phase correspopds closely to the group of intrusives which 

 followed almost immediately the appearance of the "' Acid " 

 and " Stanthorpe '' granites of New England and 8tanthorpe 

 respectively.^ 



Contact Phenomena. — A study of the contact phenomena 

 associated with the intrusion of the granites brings to light 

 a number of interesting facts. The changes brought about 

 by such intrusion vary in an apparently arbitrary manner 

 from place to place, and are often quite local in character. 

 As the main mass of granite is ap; roached from the east, 

 the schists, which normally strike in a north-westerly 

 direction, are seen to gradually change in strike, until, when 

 near the intrusive mass, they lie roughly parallel to the 

 adjacent edge of the granite. A similar phenomenon is 

 observed when the Enoggera granite is approached from 

 the west, but in this case the dip itself is reversed, the 

 schists to the west and south-west of the granite dipping 

 to the west and south-west respectively. Numerous dips 

 have been observed, and in nearly every case the schist 

 is seen to lie parallel to the edge of the granite, and to dip 

 away from it. For the smaller Green Hill and Kedron Brook 

 areas this generalisation does not seem to hold, for in each 

 of these cases the strike of the schist seems to have been only 

 locally affected by the intrusion of the magma. Indeed, 

 in the case of the former area, quite a different type of 

 structural change is brought about. This involved the 



1 . The Tin Deposits of New England, N.S.W. I. Proc. Linn. .See. of 

 N.S.W., 1909, p. 745. 



2. Compare the works of Andrews, Came, Cotton, and Saint-Smith 

 already cited. 



