33 
“ Contact 13 Metamorphic Rocks. 
“ Contact 93 Metamokpiiic Rocks. 
The “ contact” metamorphic rocks occupy zones fringing nearly 
all the granitic and trappean rock-masses where the Pakeozoic 
sedimentary rocks come in contact with them, and sometimes, 
though by no means invariably, form the walls of dykes or other 
smaller igneous intrusions. 
They very much resemble the “ regional ” metamorphic rocks 
in variety of lithological character, and exhibit the same grada- 
tions of metamorphism, though generally in a less degree, and 
with the exception that distinct boundary lines can be traced 
between them and the granite, when the latter is invasive or 
intrusive, as distinguished from the “regional” metamorphic 
granite. 
The alteration often does not consist in more than induration, or 
the addition of a spotted or slightly nodular character to the 
ordinary slates, &c. For instance, hand specimens from the 
junction of the granite and the Silurian rocks at Maldon can be 
obtained, showing granite on one side and indurated siliceous 
sandstone on the other. Near the contact of the trappean rocks 
of Mount Camel, north of Heathcote, the Upper Silurian rocks 
have been metamorphosed for a short distance to the conditions 
of jasper, chert, quartzites, and siliceous breccias. 
Breccias, made up of angular fragments of altered sandstone 
cemented by siliceous matter, occur in places near the granite 
boundary at Beech worth. At the junction of the trappean 
and Upper Silurian rocks near Lillydale, the latter are much 
indurated and in some places metamorphosed into schistose 
quartzites. 
At the head of the Buchan is a metamorphic calcareous schist 
acutely corrugated, and on the Limestone River occurs a band of 
nearly white marble. Tho “ contact ” metamorphism rarely ex- 
tends more than half-a-mile, sometimes only a few yards, from the 
granite or trappean boundaries, and in some cases has evidently 
been effected at a date subsequent to that of the “ regional” 
metamorphism, as shown in Mr. A. W. Howitt’s work, already 
referred to, on tho geology of Swift’s Creek. It may, therefore, 
be justifiably assumed that there were two phases of metamorphic 
action operating at different epochs. 
In the oarliest of these, the action was long-continued and far- 
penetrating in its effects, and the blending or transmutation of the 
sedimentary rocks with or into the plastic igneous masses which 
subsequently cooled in the form of granito took place by slow 
gradations of change. It is doubtful, too, whether the heat was 
evolved from those igneous masses or was locally engendered by 
the movements of the rocks themselves. 
In the second, or later, era of metamorphism, the transmutation 
of portions of the stratified rocks into granite was more complete, 
