322 C. H. GORDON 



of heat and pressure of the same general sort as that by which the 

 rocks themselves have been affected. 



On the other hand, the eruptive origin of these rocks has been 

 upheld by various writers. In 1884, in his report on the apatite 

 deposits, Torrence^ guardedly states that these rocks may be due 

 to contemporaneous intrusion. The apatite is regarded as due 

 entirely to segregation from the pyroxene rock and never of a bedded 

 character. In 1884 Coste^ contends strongly for the eruptive origin 

 of the pyroxenite, while the apatite is looked upon as possibly due 

 to emanations accompanying or immediately following the intrusion 

 of the igneous mass. 



Dr. Selwyn subsequently supported this view,, and said: "They 

 are clearly connected for the most part with the basic eruptions of 

 Archean date." 



R. W. Ells^ holds that, contrary to the observations of earlier 

 writers, the pyroxene rock is not interstratified with the gneisses 

 and quartzites, but occurs in dike-like masses and bands, which 

 sometimes cut across the regular stratification of the associated 

 rocks, and at other times traverse these along the bedding planes for 

 some distance, and then abruptly change their course after the manner 

 of other intrusives. In places, a gneissic structure is observed, but 

 this, as in the case of the syenite, is doubtless due to great pressure. 

 The author concludes that the apatite may be due to vapors charged 

 with phosphoric and fluoric acids ascending along the sides of the 

 dike. 



The igneous origin of these pyroxenic rocks seems to be abund- 

 antly confirmed by their mode of occurrence at High Rock, as herein 

 shown, and at numerous other places within the apatite district. 

 While in general the pyroxenites extend along the bedding plane of 

 the quartzites, they sometimes cut across the strike of these rocks 

 after the manner of intrusions, as stated by Dr. Ells. In some 

 places isolated lenticular masses of these rocks or a similar horn- 

 blende rock appear along the bedding plane of the quartzite, which 

 are inexplicable except on the theory that they represent cross- 



^ Geological Survey of Canada, Report of Progress, 1882-83-84, Report J. 



=> Ibid., 1887-88, Report S, p. 64. 



3 Canadian Record of Science, January, 1895. 



