176 W. N. BENSON. 



PRELIMINARY NOTE on the NEPHELINE-BEARING 



ROOKS OF the LIVERPOOL and MOUNT ROYAL 



RANGES. 



By W. N. Benson, b.'so. 



With Plates VI, VII. 



[Bead before the Royal Society of N. 8. Wales, August 2, 1911, .] 



About two years ago, when first in the Nundle district, 

 the writer noticed the great abundance, in the gravels of 

 the Peel River, of pebbles of a remarkable coarse-grained 

 basic rock with large dark purple-brown phenocrysts of 

 augite. An examination of slices of these under the micro- 

 scope showed that the augites were strongly zoned, some- 

 times having the hour-glass structure, and were highly 

 titaniferous, while there were a number of large apatite 

 prisms. The general facies strongly recalled the famous 

 nepheline dolerite of the Lobauer Berg in Saxony. Never- 

 theless no nepheline was detected, the salic mineral being 

 labradorite. Similar rocks were found later at Crawney, 

 probably in situ, some fourteen miles further up the river 

 than Nundle. Want of time prevented the investigation of 

 their field relationships. While on a brief visit to Goonoo 

 Goonoo, a small pipe of the rock was found forming a slight 

 elevation (Ourrajong Hill) about a mile south-east of the 

 station. A further large extension of these rocks was 

 suggested by the following observation made by Mr. E. O. 

 Andrews: — "At the Hunter and Manning River headwaters 

 two distinct basaltic types occur, one a noncrystalline 

 rock with large augite crystals so abundantly scattered 

 throughout its mass as to obtain for it locally the name of 

 4 plum pudding stone.' Other types found here are dense 

 fine-grained vesicular olivine basalts.' ' 



1 Tertiary History of New England, Eec. Geol. Surv. N.S.W., Vol. 

 vn, pt. 3, p. 63, 1903. 



