586 GREAT SERPENTINE-BELT OF NKW SOUTH WALES, V., 



The tectonic features of the serpentine-intrusion differ from 

 those normal elsewhere in the Serpentine Belt, in the sudden bend- 

 ing of the serpentine into a north-north-easterly direction, where it 

 approaches the granite. That this is not due to the wedging out- 

 wards of the strata by the invasion of the granite, is shown by the 

 fact that the strike of the Devonian rocks continues almost un- 

 changed, and is cut obliquely by the serpentine. We may, perhaps, 

 see in this some evidence that the stresses, which determined the 

 Cockburn River axis of folding, had begun to make their influence 

 felt when the intrusion of the ultrabasic rock occurred. 



Moonhi Granite. 

 About fourteen square miles of the area covered by the 

 present map are occupied by granite. This is the southern 

 extremity of a batholith which extends from Bendemeer to the 

 north, in the direction of Attunga, to the north-west. Accord- 

 ing to Mr. E. C. Andrews(12), it is invaded by the more acid 

 granite of Bendemeer, which forms resistant masses that stand 

 out in relief above the more basic Moonbi granite. On the east, the 

 granite is bounded by the jasperoid rocks of the Eastern Series, 

 which, also have a high relief, and form the prominent peak of 

 Bullimballa( Black Jack), about six miles to the N.N.E. of Moonbi. 

 Both these prominences are, however, outside the limits of the area 

 under discussion. 



The granite is of coarse or medium grainsize, even-grained, or 

 slightly porphyritic. It is fairly potassic, containing a consider- 

 able amount of orthoclase and biotite. Hornblende is the dominant 

 coloured constituent, and sphene is generally present in notable 

 amount. Mr. Andrews lias compared this granite with the sphene- 

 granite-porphyries of northern New England, to which he attri- 

 butes an early Mesozoic age(12). 



The granite is invaded by a variety of vein-rocks; aplites, with 

 druses containing crystals of quartz with a mica like zinnwaldite, 

 occur associated with veins of quartz bearing small amounts of 

 molybdenite, in the high ridge between the Cockburn River and 

 Moore Creek. Various types of pegmatite, either graphic quartzose 

 pegmatite, or more richly felspathic rocks, often containing a little 



