124 THE PENOKEE IRON-BEARING SERIES. 



or less urbitrar}'. In the field the massive [!;nuiite, gneissoid granite, grani- 

 toid gneiss, coarse gneiss, and fine grained ■ gneiss are sometimes found in 

 order in passing- from a granite into a scliist area. This change has not 

 been found in continuous exposure, l)ut in detached ones. More frequently 

 a different relation is found, the fine grained crystalline schists being cut l)y 

 massive granites in such a manner as to leave no doubt of the eruptive 

 nature of the latter. In passing from a schist to a granite area, there first 

 ai)pears cutting the schists rare small veins and stringers of granite; then 

 the o-ranite- is found in dike-like forms or in masses and bosses within the 

 schist. Next, the granite becomes predominant, and finally the schisls 

 altogether disappear as we get wholly within a granite or gneissoid granite 

 area.^ The old interpretation placed on such apparent transitions from 

 finely schistose to massive rocks has been that metamorphic agencies have 

 transfoi-med the crystalline schists into the massive granites. It has been 

 taken for granted that the strongly schistose, finely laminated phases nuist 

 be of sedimentarv origin. This being' the case, their gradation into massive 

 rocks was taken as proof of the derivation of the latter from the former by 

 metamorj)hosiug agencies; that is, moisture, heat, and pressure have re- 

 crystallized the rock, giving it a coarsely crystalline granitic structure in 

 place of the finely crystalline schistose one. This interpretation is based 

 upon the assuuijjtion that the strongly foliated schistose rocks are of sedi- 

 mentary origin. If this is unproval)le tlie conclusion is valueless. At the 

 present time this derivation of massive syenites and granites from schist(»se 

 rocks l)y metamorphosing agencies is greatly discredited. It is almost 

 universally believed that massive granites, syenites, and gabbros are of 

 eruptive origin. If this is assumed, there seems to be no escape from the 

 conclusion that a large proportion of the crystalline schists and gneisses of 

 the area were originally eruptives. 



' These relations are similar to tlioae <lescril)('<l by Dr. Audrt- \v C. Lawsciii, <>1" tbi- Cauadiau Oeo- 

 logical Survey, as occurring between thi- Kiiwatin .mil ('oiitchicliiiiu series, ami the assdcialed 1 au- 

 rentiaii <{raiiites and gneisses. Keport (lu tlie Gei)h)i;v of the Kaiiiy Lake Kefjion, .\ndre\v C. Lawsoii, 

 Animal Keport iif tlie (;e(ib)frieal and Na(nral lilslory .Survey of Canada lor 1SS7, Altred K. C. Selwyu, 

 direetor; part F, )>p. 1-182. In this paper Dr. Lawson maintains that the grauite whieh is assoi- 

 eiated with and cuts the schist has been produced by the fusiou of the schists, thus chanuim^ them 

 to truly igneous rocks. ' 



