METAMORPHIC ROCKS OF THE OMEO DISTRICT, GIPPSLAND. 217 



The Frenchman's Hill is one of those more recent irruptions of 

 wliich I have said that they now stand out of the areas of 

 intrusive plutonic rocks in various parts of the district. The 

 main rock-masses which surround this hill are granites which 

 terminate on its north-east side at the fault, beyond which are 

 situated the mica-schists and other less altered sediments. The 

 granitic rocks have invaded the schist formations both horizontally 

 from the fault, and from below upwards, appearing as appophyses 

 and isolated patches, as well as in dykes. 



To the westward of the Livingstone Creek, which floMs at the 

 base of the Idll, the granites seem to pass into diorites, by tlie 

 replacement of orthoclase by plagioclastic felspars. 



Younger than the granites and intrusive into them, are masses 

 of holocrystalline rock composed essentially of orthoclase with 

 subordinate triclinic felspars, quartz, and a little muscovite mica. 

 To this class of rock in this district I have applied the term aplite. 

 These rocks not only occur as intrusive masses of some extent, 

 but also are to be found in the mica- schist both as masses and 

 dykes, and even small veins lying between the schist beds or 

 crossing them. In places these aplite veins are so coarse in 

 texture, as through a further accession of muscovite to become 

 muscovite granite or pegmatite. 



Younger than the aplites, and again intrusive as regards them 

 and the granites, are masses of rock composed essentially of 

 orthoclase. In one variety the orthoclase is in more or less perfect 

 crystals, and the interspaces between them are filled by a grano- 

 phyric mixture of felspar and quartz, with the interspaces between 

 them finally filled by limonite, which shows traces that the original 

 mineral was haematite. 



Another variety of this class of rock consists of orthoclase 

 felspar, with imperfect bounding planes in a ground mass of the 

 same, in much smaller individuals, and a little quartz. A third 

 variety is formed by a network of lath-shaped crystals, with rarely 

 lai'ger porphyritic ones. Finally there is a variety which consists 

 wholly of minute felspars, with little more than a trace of free 

 quartz. This latter form occurs as dykes, sometimes of considerable 

 width and great length, as well in the immediate neighbourhood 

 as at a distance from the mount. 



It must be noted that in some samples I have found a small 

 percentage of biotite, which in one variety amounted to an 

 essential part.* 



These rocks, which are all younger than the aplites, belong, 

 as a whole, to the group called orthophyr, or orthoclase por- 

 phyries. 



The samples which contain a considerable percentage of biotite, 

 approach the mica-syenites, but in somewhat aberrant variations. 



* III all the analyses which I have made of these rocks I have found a percentage of Na„ q 

 larger than the microscopic examination would have led me to expect. 



