Notes on the Area of Intrusive Rocks at Bar go. 163 



(3.) The elevation of tlie crust of the earth to a land 

 surface during the early part of the Devonian age, and the 

 manifestation of plutonic action in volcanoes (Snowy River 

 district). 



(4.) The cessation of the plutonic and volcanic action and 

 the subsidence of the land in the Middle Devonian period. 



(5.) The intrusion of the quartz diorites of Dargo was 

 probably during the latter part of the time mentioned in (2). 



(6.) The formation of the auriferous contact and other 

 quartz reefs of the district referred to in these notes was 

 probably in some part of the time mentioned in (3), if not 

 in the earlier part of (4). 



These, then, are the general conclusions which I have 

 reached as to the origin and formation of the auriferous 

 reefs of North Gippsland, whether at the contacts or in the 

 Silurian formations. The tentative hypothesis which I have 

 briefly sketched pretends to no more than an attempt to throw 

 some light into the dark places of a most difiicult subject. 

 Whether I have in any measure approached a solution of 

 the question I must leave to competent authorities to decide, 

 merely adding that, from my point of view, the hypothesis 

 seems to harmonise with observed facts, and not to run 

 counter to the requirements of geological chemistry. 



My views, if resting on a foundation of truth, would have 

 an important bearing upon the question of the future con- 

 tinuance of our quartz reefs in depth. It would follow as a 

 corollary to them that the quartz reefs in any part of 

 Victoria might be expected to descend in a more or less 

 connected manner through the whole thickness of the Silurian 

 formations, and to end only as contact lodes at the sub- 

 terranean plutonic rocks. 



EXPLANATION OF THE PLATES. 



Plate I. 



Horizontal plan of middle adit at the Exhibition mine, 

 Orr's Creek, Dargo, looking west. The numbers 1, 2, 3, 4, 

 refer to the sections given in the plate across the adit. 



Fig. 1. (a) Quartz vein six to nine inches wide, with gold, 

 accompanied by galena and ordinary iron pyrites. (6 

 and h') Narrow quartz veins carrying gold, very finely 

 divided, and being in places merely thin partings, (c) 

 Hornfels rock. 



M 2 



