190 president's address- — SECTION c. 



-veins have been found cutting the gneissic series. While the junction 

 with the gTanodiorite is everywhere sharp, no such junction with the 

 normal dacite has been seen, but there appears to be a gradual tran- 

 sition from a gneiss through less and less gneissic dacites to the 

 normal rock. This I regard as strong evidence that the dacite is the 

 older rock, and that the subsequent intrusion of the granodiorite into 

 •the already consolidated dacite has altered the latter rock near the 

 • contact to a gneiss, while in the final stages of consolidation of the 

 granodiorite, pegmatite and quartz veins penetrated the gneissic 

 rock. 



The Warhurton District. — A somewhat similar belt of gneissic 

 rocks was found by me in 1906 to separate the granodiorites which 

 lie to the South from the normal dacites lying to the North of War- 

 burton. These are best seen in Pheasant Creek, about a mile to the 

 east of the township. A sharp junction with the granitic rock occurs, 

 but apparently they merge into the unaltered dacites to the north. 



At " Nyora," between Healesville and Launching Place, and about 

 2 miles north of the latter, the granodiorite and dacite also junction. 

 In this locality no gneissic band intei^venes, but acid veins can be seen 

 running into the dacite from near the junction with the granodiorite. 



The Black's S-pur and Narhethong areas. — On the Geological Sur- 

 vey Map of Victoria (1902), on the scale of 8 miles to the inch, a 

 junction between the two series is shown, close to the Hermitage, 

 iDetween the Black's Spur and Narbethong. Prof. Gregory states that 

 here the dacites rest on the granodiorite. I spent three days in the 

 locality looking for this junction, but it does not occur where it is 

 shown on the survey map. The map indicates a great mass of 

 granitic rocks extending from near Narbethong through Marysville, 

 north-east to Mount Torbrech, whereas over most of this area the rock 

 is certainly dacite. 



The Marysville District. — Dacite is widely spread near Marys- 

 ville. The rock is mineralised in places. Gold has been worked in a 

 creek running only over dacite, near the Wood's Point road, about 7 

 miles to the east of Marysville. 



Six or seven miles to the S. of Marysville and on the south of 

 the divide wolfram and scheelite have been worked. On a visit to the 

 wolfram workings, which I made in 1908, I found that they occurred 

 near the junction of the dacite with a granite-porphyry. Tlie actual 

 junction was not seen, but there is little doubt that the granite- 

 porphyry is intrusive into the dacite, since acid veins and quartz 

 veins carrying wolfram and scheelite penetrate the dacite near the 

 contact, and some of these have been worked for these minerals. 



The Gerherean Eange, north of Marj^sville, also consists of dacite. 

 The Macedon Area. — Prof. Gregoiy, as mentioned above, regards 

 the dacites as younger volcanic rocks, with minor intiaisions, poured 

 out over the denuded surface of sedimentary rocks and granodiorite. 

 Mr. Summers and myself have mapped the whole district, and find 

 that, although no gneissic rocks occur near the junction, minor 

 structural and mineralogical changes occur in the dacite at the con- 

 tact. We also find tourmaline and acid granitic rocks developed at 

 the contact, and small acid pegmatitic veins in the dacite near the 

 granodiorite, and for these reasons regard the dacite as the older 

 rock, and the granodiorite as intrusive into it. 



