258 H. IS. Siirmnera: 



Northward from Healesville in the Cerberean Range, and in the 

 northern portion of the Strathbogie Range, a rather coarser rock 

 is the prevailing type. Taking the occuri-ence at the road-metal 

 (^uarry at Violet Town as a type of the Strathbogie rocks, the fol- 

 lowing brief description may be given here. 



This rock consists of phenocrysts of plagioclase (acid labradorite). 

 abundant biotite, sparing hypersthene with a moderal)le auifiunt of 

 ■quartz in a granulitic groundniass similar in evciv respect to that 

 describetL above as uccui-ring in the dacite, except tliat it is some- 

 Avhat coarser in grain. The phenocrysts aie distinctly larger than 

 those found in the dacite, and there is a largei- amount of free 

 quartz present. Garnets are ncjt unconunon throughout this area. 

 An analysis of the material from the Violet Town (juai'iy ^vas made 

 ■a few years ago for me by Mr. G. Ampt, Init has so fai- not been 

 published. This analysis, which is given later, compares faii'ly 

 •closely with those of the dacites, but as was expected from the micro- 

 scopical examination, it shows a decidedly higher percentage of 

 silica. 



The chemical and mineralogical characters of this rock are suffi- 

 ciently closely allied to those of the Macedon dacites to cause us to 

 regard them as genetically related to one another. 



The southern portion of the Str.athbogie Ranges consists of a 

 granitic rock which provisionally may be lefei'i-ed to as adamellite. 

 Frequently there is no hard and fast line of demarkation between 

 the (juartz-poiphyrite of the northern poition and the adamellite 

 of tho southei-n. To the soiitliwai'd the quartz porpliyrite liecomes 

 much coarser in grain, and might well be desci'ibed as adamellite 

 po)-phyry, and in places passes imperceptibly into adamellite. Xoar 

 Euroa tlio junction is more marked, as a fairly broad area of eveii' 

 grained aplitu is found separating the adamellite porphyry from 

 the adamellite. An examination of the junction of this aplitii' 

 i-ock with the porphyry shows that the aplite is intrusive into the 

 lattei-, as veins from the former can easily be traced running out 

 fi-om tho main mass into the adjoining ])ori)liyry. The relations 

 of the a))lite to the adamellite are not so clear, but apparently the 

 ajilite is also inti'usivo into the adaiiu'lliti'. The inference I make 

 from a study of this held is that the iiuartz porpliyrite and adamel- 

 lite porphyry are the oldei' I'ocks, and that as in the case of the 

 Macedon and other dacite areas, the granitic rock was subsequently 

 intruded. The difference noted l)etween tlie contact in the dacite 

 areas and in this area may be due to the fact that the dacite was 

 largely effusive, whereas the field evidence and microscopical 



