HYDRON SILICATES IN ROCKS OF CONCEPTION BAY 151 



haps indirectly through mingling with already aluminous solutions. 

 Such solutions, if present, would be those which had accomplished 

 the silicirlcation of the volcanics with their attendant solution of 

 alumina under static conditions and hence before the period of 

 orogenic movement, which folded the volcanics and witnessed the 

 intrusion of the plutonic batholith and stock. The evidence bear- 

 ing on the exact dates of the periods of faulting and folding, however, 

 is not conclusive. 



COMPARISONS WITH OTHER DEPOSITS 



Comparisons with other deposits show that, according to the 

 descriptions, the pyrophyllite deposits of the Pambula goldfield, 

 New South Wales, and of Chatham and Moore counties, North 

 Carolina, are essentially similar to those in Newfoundland, and it 

 is here suggested that possibly they have had a similar origin. 



Clapp (1914) described quartz-pyrophyllite rocks from Kyuquot 

 Sound, Vancouver Island, which may be taken as a type of pyro- 

 phyllite deposits developed by solfataric agencies under conditions 

 of temperature and pressure existing near the surface; while those 

 of Newfoundland are a type originating under intermediate con- 

 ditions of temperature and pressure. 



In the first case the pyrophyllite rocks are associated with 

 alunite and in the latter case with pinite. In the Kyuquot deposits 

 the original quartz of the replaced dacite has not suffered any loss 

 except in one doubtful case, while the distinctive feature of the 

 Newfoundland rocks has been the replacement of quartz in rhyolites 

 by pyrophyllite. 



The two deposits are similar in that, in both cases, the rocks are 

 associated with intrusive batholiths, the one with a feldspathic 

 quartz diorite and the other with granite. Both are metasomatic 

 replacements of acid volcanics, while in the zone of alteration there 

 seems to have been some transfer of material, and soda, lime, 

 magnesia, and iron oxides have been lost in each case. 



CONCLUSION 



From the foregoing evidence the conclusion may be drawn that : 

 the pyrophyllite, pinite, and quartz-pyrophyllite schists of the 



