BY W. N. BENSON. 585 



had tlie same g'eneral range. [The evidence for this statement has 

 been recently summarised by Grabau(21)], 

 Serpentines, etc. 



As in the areas described in former papers, the serpentine 

 follows the line of fault, which separates the highly disturbed 

 rocks of the Eastern Series, from the less crumpled rocks, 

 which lie to the west. The band of serpentine varies greatly in 

 width. At the southern end of the map, on Nemingha Creek, it is 

 not more than 50 yards across, and is even narrower a short dis- 

 tance to the north. It is much broader at the head of Spring- 

 Creek, being nearly 300 yards wide there, and then tapers gradu- 

 ally northwards, dying out completely in Portion 144 of Nemingha 

 Parish. The fault-line may, however, be traced into Portion 169, 

 where there is a small lenticular area, about ten yards long, com- 

 posed of ferruginous carbonate rock, such as represents the serpen- 

 tine in other jDortions of the Serpentine Belt, as in the Nundle and 

 Crow Mountain districts. 



The serpentine is mostly of the sheared, chrysotilic variety; 

 some massive bastite-serpentine is present, and a little antigoritic 

 rock. Other alteration-products are rare. A ehalcedonic replace- 

 ment of bastite-serpentine occurs in Portion 176, and opal, with 

 dendritic markings, in Portion 129. Near this was found a small 

 patch of olivine-gabbro, only a few yards in extent. The felspar 

 of this rock was converted partly to saussurite, and partly to clino- 

 zoisite. Small segregations of chromite occur in the serpentine. 

 With this, hyalite has been found by Mr. D. A. Porter(4^. 



In several places there are abundant intrusions of a porphyritic 

 or massive dolerite in the serpentine. This rock has exactly the 

 same characters as that occurring in a similar situation in the 

 neighbourhood of Bowling Alley Poir»t(l7,p.l56), The individual 

 masses are quite small, ten or twenty yards long, and about half as 

 wide. Some are rather sheared. None appear to cut the serpen- 

 tine transversely, but the individual masses may be fragments of 

 larger instrusions torn apart by movements in the body of the 

 serpentine. No dolerites of this character have been found outside 

 of the serpentine. 



12 



