Geology of (he l>iariioad Creek Area. 333 



to be extensively developed near the Templestowe anticline, and the 

 joints are seen to be mainly strike joints, and are probably con- 

 nected with the folding of the sediments. 



(d) Fault} in/. 



Two main periods of faulting have been noted : — 



1. Pre-mineralisation. 



2. Post-mineralisation. 



As examples of faulting previous to the formation of the quartz 

 reefs, we have the brecciated zone, now occupied by the Diamond 

 Creek dyke, and probably the slips parallel to the bedding plaries 

 belong to this period. Movement later than the formation of the 

 reefs is well illustrated by tlie numerous strike faults occurring in 

 the Union and Diamond Creek mines. This type of faulting has 

 not been recognised elsewhere in the area, although it is possible, 

 but not probable, that such fatdting has been missed, due to the 

 fault planes coinciding with the dip of the beds. 



As regards igneous intrusions, the basalts and acid dykes have 

 already been described under stratigraphy. Only two basic dykes^ 

 from the area are known to the writer. One was found by Howitt^ 

 at the Caledonia mine, Warrandyte, and was determined by Pro- 

 fessor Skeats as a monchic[uite, and the other was found by the 

 writer in section 16, and is described later. 



6.— Petrology. 



(a) Sandstones and their origin. 



Several sections of the sandstones from various parts of the area 

 have been examined by the writer. Section A18 from the Watts 

 River aqueduct near the AVarrandyte anticline is a typical example. 



In hand specimen it is seen to l»e a dark-coloured, dense, micaceous 

 rock . 



Microscopically the foUoAN ing minerals arc recognisable : — Quartz, 

 muscovite. chlorite, tlint. t<>ur-malinc. zircon, rutile, apatite, mag- 

 netite, leucoxene. biotite, plagioclase, iron oxides and patches of 

 carbonaceous material. Quartz occui's in all sections examined in 

 well over 90 per cent, of the rock. Tlie grains are either angular 

 er subangulai', and are very rarely rounded. Numerous micro- 



1 Tlie writer has since seen in the National Mdsenni, Melhourne, a specimen of j/iira lanprn- 

 pkyre from the liiioii Mine, Diamond Creek. 



2 A. M. Howitt. Notes on a Sketch Survey, of the Caleilonia Reefs at Warrandyte. Kept. CJeol. 

 Surv. Vict., vol. 3, Pt. I, 1900, p. 40. 



