10 Proceedings of the Royal Society of Victoria. 



cooling mass after the original severe lateral pressure had been 

 relieved, but this is a less likely explanation on several grounds. 

 The planes of fracture would, in whatever way in which they 

 were formed, become convenient courses at a later date for water 

 currents in the earth to take, these would bring with them the 

 minerals subequently deposited. The deposit has evidently not 

 been completed at one period of time, for although there does 

 not appear to have been the phenomenal surface enrichment of 

 the lode seen on many of the Victorian fields, yet there is the 

 enrichment of the lode in copper to be accounted for at the 

 places adjacent to the main east and west fault plane. 



At Mount Elmo the plane of weakness was evidently given by 

 the still distinct bedding planes between the quartzites and schists 

 whilst the two impervious beds of quartzite kept the subsequent 

 water current to a definite course and with it the deposit. In 

 the case of Lightning Creek, metamorphosis had not proceeded to 

 so great an extent, and in the absence of dykes or fault planes 

 the deep seated aqueous currents were not so confined — so that 

 even though rich deposits of gold could and did occur they were 

 individually smaller and generally more diffuse. Although in all 

 probability belonging to the same period of time it presents the 

 extreme opposite case to the concentration of mineral seen at 

 Bethjinga, owing to the different degree of permeability to 

 aqueous currents that it possessed. 



EXPLANATION OF PLATE I. 



Fig. 1. — A typical section of the gneiss. There is hornblende {h) 

 — pleochroism very pale yellow to pale brown, Silli- 

 manite, (S) — occasionally as single inclusion in quartz, 

 but more often occupying areas amongst the horn- 

 blende. Biotite Mica {b) Cordierite {c) generally as 

 simple prismatic crystals grouped and single and lying 

 amongst biotite or in quartz {q) this latter showing 

 much strain figure in polarized light. The felspar 

 (/) are both of twinned and simple areas. 



Fig. 2. — Is an actual section taken from one of the felspathic 

 aggregations in the gneiss in the lower part of mine. 

 There are garnets [g) each more or less completely 



