THE GOWGANDA LAKE DISTRICT, ONTARIO 



669 



(magnesia, iron, alumina, silicate) and analysis shows that the most 

 altered parts are also richer in potash. 



There is of course no check on original variation in the composi- 

 tion of the sediment, but the results accord so well with what would 

 be expected, if the granophyre was formed as here imagined, that 

 they are to be regarded as, in some degree, corroborative. 



The partial analyses, Nos. IV and V, Table III, of the altered 

 sediment (adinole) near the Lost Lake granophyre, together with its 

 microscopic examination, show it to be an albite-quartz rock approxi- 

 mating the granophyre in composition. The nearly pure albite 

 layer, No. Ill, Table III, between granophyre (recrystallized adinole) 

 and adinole probably separated from the fluid granophyre. Albite 

 is certainly in excess in the granophyre (note phenocrysts) and its 

 separation toward the adinole would be especially favored by the 

 composition of the latter. 



That the granophyre "solution," formed as here imagined, was 

 foreign to the diabase magma is indicated by the intense alteration 

 of the constituents of the diabase near the granophyric interstices.^ 



The aplitic veins^ (quartz and albite, often with calcite) which cut 

 both granophyre and diabase were formed from the more aqueous 

 residuum of the granophyre. They are especially numerous near a 

 mass of granophyre. The extreme purity of their albite (note analy- 

 sis No. V, Table II) points to their aqueous origin, as does also 

 their calcite content. This aqueous residuum probably deposited 

 also the valuable metallic content of the aplite veins and of the asso- 

 ciated calcite veins. The association of gold with the similar soda- 

 rich rocks of Alaska, California, and Ireland is worthy of note (see 

 p. 671, below). 



I See A. E. Barlow, Jour. Can. Min. Inst., XI (1908), 271. 

 » N. L. Bowen, Jour. Can.' Min. Inst., XII (1909), 95-106. 



