177 



GEOLOGICAL NOTES ON THE BARRIER RANGES 



SILVER EIELD, 



By C. W. Marsh, Urnberumberka. 



[Read before the Royal Society of N.8.W., November 5, 1890. .] 



The Barrier Ranges Silver-field is situated near the western 

 border of New South Wales, and immediately east of the South 

 Australian boundary, its distance from Sydney being about 600 

 miles, in a direction slightly north of west. The portion to which 

 the silver deposits are more particularly confined comprises an 

 area of about 800 square miles, having, from the Angus and 

 surrounding claims on the south, to Mount Robe, Black Prince, 

 War Dance, &c, on the north, a length of about 40 miles, and 

 from the Thackeringa, Urnberumberka, Day Dream, and other 

 mining properties on the west, to the Rockwell Paddock claims 

 on the east, a width of about 26 miles. This silver-bearing 

 portion of the ranges consists of low undulating hills with broad 

 valleys and flats, the hills being principally gneissic or hornblendic 

 rocks, while in the valleys and flats in most cases are found the 

 softer micaceous, talcose and chloritic schists. 



The more or less parallel strike and dip of these rocks, together 

 with their different powers of resistance to disintegrating agencies, 

 have resulted in an irregular lineal arrangement of hill and valley 

 in a north-easterly and south-westerly direction. The strata- 

 graphical structure of these ranges is synclinal, the rocks on the 

 western side dipping east, at or about 60 degrees, rising to the 

 horizon again on the eastern side at nearly the same angle ■ and, 

 though we may not be able to recognise on each side rocks of 

 precisely the same order and character, the differences are not 

 greater than we should expect, considering the changed conditions 

 under which these separated deposits may have taken place. 



Besides the main synclinal fold, whose limits are hidden beneath 

 the sediments of the eastern and western plains, there are numer- 

 ous small folds arising from the effects of local pressure, causing 

 many changes in the dip and strike of the surface rocks. While, 

 irrespective of the synclinal fold and other modifications, there 

 appears to be a general bodily dip of the country to the southward. 

 The more argentiferous rocks occupying the upper or inner 

 portion of this synclinal fold appear, so far as observed, to rest 

 upon a series of strata made up principally of highly granitic 

 gneisses with calcareous and argillaceous schists ; greenstones 



L— November 5, 1890. 



