GEOLOGY OF NUXDLE DISTRICT. 103 



olivine basalts, doleritic types, and rarely scoriaceous basalt. 

 Associated with these is a nepheline basanite, typically developed on 

 Square Top, near Nundle. The relation of these to the normal 

 basalt has not yet been determined. It may be mentioned, how- 

 ever, that there is a series of nepheline rocks extending from Nundle 

 southwards to the Mount Royal Range, and these appear to be 

 intimately associated with the normal tertiary basalt. The writer 

 has in preparation a note descriptive of these. 



Following on the basaltic eruption there have been periods of 

 uphft and dissection producing the present physiography, which 

 has been briefly described by Mr. E. C. Andrews. Want of space 

 forbids a discussion of many interesting points in this connection. 



During the grading of the Peel River at least two sets of gravels 

 have been produced, sometimes giving rise to terracing on a small 

 scale. 



Economic Notes. — Gold was first found in this district in 1852, 

 and since then about £750,000 worth has been obtained. It occurs 

 in many ways : — (a) In quartz veins near the boundaries of the 

 diabases ; (6) in quartz veins in slate away from the diabases ; 

 (c) as impregnations in slate in wide low-grade channels with rich 

 quartz stringers ; {d) as impregnations in carbonated serpentine ; 

 (e) in tertiary drift, mined by hydraulic sluicing ; (/) in high-level 

 river gravels ; (g) in the present river gravels, won by dredging, 



Scheelite occurs in small quantities in most of the modes of 

 occurrence noted for gold, but of these the first two only seem to 

 have yielded payable amounts. In the slate it forms lenticular 

 bunches. Stibnite occurs near Nundle seemingly in a brecciated 

 fissure vein in slate, parallel to the strike. Chromite forms large 

 segregations in the serpentine, but for the most part is of low grade. 

 The white marble does not form deposits large enough to work for 

 statutory marble, and is difficult of access, the red marble is in 

 greater quantity, is easy of access, and takes a good polish. Zircons 

 and sapphires have been found in the interbasaltic layers, but not 

 of large size. 



The map (Plate II.) has been drafted from a plane-table survey 

 by the writer. The smallness of the scale has prevented the 

 showing of much detail that might well have been added. The 

 many intrusions of porphyry are shown to occur chiefly in the 

 Woolomin Series, but the largest of them is at B on the section line, 

 in the Nundle Series. The hmestones of the Bowhng Alley Series 

 are shown as solid black patches. The intrusions or flows of 

 andesite in the sedimentary series have not been indicated, nor have 

 the layers of andesitic tuff. The epochs of intrusion stated for the 

 plutonic must be taken chiefly as indicating the relative order of 

 their intrusion ; the serpentine may be early carboniferous, and 

 the gabbro diabase consequently rather more recent than indicated. 

 The occurrence of serpentines as erratics in the glacial permo- 

 carboniferous age proves that these cannot post date the carboni- 

 ferous. Particularly with regard to the age of the granodiorites 

 there is much uncertainty. That they are not remarkably acid 



