2 FRANK D, ADAMS 
almost every exposure inclusions which represent the last scattered 
remnants of the invaded rock. 
In addition to these intrusions of Laurentian granite-gneiss, there 
occur in the area, also cutting the Grenville series, great intrusions of 
gabbro and great bodies of nepheline syenite.t_ These massive intru- 
sions of gabbro are frequently intimately associated with and partly 
inclosed by bodies of amphibolite which are classed as belonging 
to the Grenville series. ‘The whole forms a very complicated and, at 
the same time, a very interesting stratigraphical complex, as will be 
seen by consulting the Bancroft or Haliburton geological map sheets 
recently issued by the Geological Survey of Canada. The former 
sheet is also to be found accompanying the paper on this region which 
has recently appeared in the Quarterly Journal oj the Geological 
Society of London.? 
The inability to determine the origin and, therefore, the signifi- 
cance of the bodies of amphibolite which occur abundantly not only in 
this district, but everywhere throughout the Laurentian, has always 
proved to be one of the chief difficulties in the way of a correct 
interpretation of the geology of this system. The same difficulty 
has been met with in the case of these and allied rocks occurring 
elsewhere, as, for instance, the trap granulites of the Saxon Granulit 
Gebirge, or the amphibolites of the crystalline complex of certain 
portions of the Alps, the origin of which remained in doubt while 
the rocks with which they are associated had been definitely deter- 
mined. 
It is the purpose of the present paper to present briefly the results 
of a study of the genetic relations of the amphibolites of this particular 
area in the Canadian Protaxis. 
The amphibolites in the area in question present a considerable 
variety in character and appearance but have as common character- 
istics a dark-gray to black color and a basic composition. Hornblende 
and feldspar, the latter chiefly plagioclase, are the chief constituents 
of the rock. Quartz, which is one of the commonest constituents 
t See Adams and Barlow, “‘The Nepheline and Associated Alkali Syenites of 
Eastern Ontario,”’? Transactions Royal Soc. Can., 1908. 
2F. D. Adams, “‘The Laurentian System in Eastern Canada,” Q. J. G. S., 1908, 
DeayL2ie ‘ 
