ECONOMIC GEOLOGY OF THE ARCHEAN. 347 



does not reach to the probable southern extension of the great fault in 

 the western part of Steep Hock lake. These quartz porphyries become 

 distinctly finer grained in the vicinity of the Steep Rock series to the 

 northwest anoVwest and less certainly so as the massive altered traps to 

 the south are approached. They are extremely massive and coarse- 

 grained in the intermediate portions. The altered traps to the south, 

 the writer thinks, belong to the Keewatin, being succeeded in descending 

 order by chloritic, hornblendic and micaceous schists and Laurentian 

 granites. The quartz porphyries appear to be a unit mass erupted, since 

 the deposition of the Steep Rock series, along a probable fault plane or 

 line of contact between the underlying Laurentian and Keewatin rocks, 

 presumably the line of weakness. They extend several miles to the east, 

 north of and rudely parallel to the general direction of the Atic Oban 

 river, and send out long apophyses northeast into the Seine granite area. 

 Their contact with the " greenst* me " to the south seems to be less irregular. 



The introduction into the already confused Archean nomenclature of 

 the unnecessary term "Atic Oban series " is to be deprecated, as it can 

 only include this unit mass of eruptive rock, the correlation of which 

 with other similar masses must always be uncertain. 



Whether the eruption of these quartz porphyries preceded or suc- 

 ceeded the great oratechnic movement which buckled the Steep Rock 

 series must remain as yet an open question. Their massive character 

 on Margaret lake favors tin; view that they are of later date than this 

 movement. On the other hand, they are here found in their broadest 

 development, and their mass and perhaps a superior hardness may 

 have enabled them to resist this pressure. In the terminations of the 

 apophyses which they send into the Seine area of granites the rocks are 

 found to be intensely crushed ; and if the isolated bands of crushed and 

 sheared quartz porphyries which are found in the Seine area northeast 

 of Steep Rock lake are of the same age, they must have antedated this 

 lateral pressure. 



Economic Geology of the Arciiean. 



Present Knowledge superficial. — Our knowledge of the economic geology 

 of the Archean rocks is purely superficial, as no real mining has been 

 done and no facilities are thus afforded for an exhaustive study of the 

 ores and their intimate relations. The writer cannot refrain from ex- 

 pressing his opinion here that the laws of Ontario are primarily to blame 

 for this stagnation in mining. As they encourage every evil tendency of 

 mining speculation and discourage every attempt at scientific exploita- 

 tion and healthy development, the mineral wealth of this undeveloped 

 country remains unimproved and unremunerative. 



