280 University of California Publications in Geology [Vol. 13 



deepest veins different in composition from the upper portions of the 

 outcropping veins, there being no evidence that either silver or the 

 other metals ever existed in that region in any other condition than 

 that in which they are found just below the outcrops. Furthermore, 

 no veins at any time in the camp's history have shown consistent 

 oxidation to a depth of more than a few inches or feet, except in two 

 or three anomalous cases due to peculiar local conditions ; and no con- 

 sistent nor even certain enrichment has been found below these insig- 

 nificant zones of oxidation. Generally where arsenides outcrop they 

 are fresh and unoxidized, or only crusted with a thin layer of erythrite 

 or anabergite. Many veins which have proven rich in their lower 

 portions grade upward into barren arsenides and then into unmixed 

 calcite. In addition to these facts it is important to recognize that 

 the water table throughout the northern portion of the Province is 

 virtually at the surface ; and it is highly improbable that it has ever 

 been lower. 



Ascending solutions. — After many years of mining it has become 

 strikingly apparent that the ore bodies are distributed marginally 

 with reference to the sheet of Nipissing diabase. Probably the depo- 

 sitions of ore were equally distributed with reference to both margins ; 

 so far as available evidence goes, that is true ; but on account of erosion 

 the chief production of the district has come from beneath the dia- 

 base. If the source of the ore were the visible diabase mass, it would 

 be difficult to understand how this condition could have been brought 

 about by ascending waters. If another igneous soiirce is assumed it 

 must have reached the level of the present surface, or have betrayed 

 itself in some other manner; or else it must lie far below the present 

 surface ; but no such intrusive synchronous with or subsequent to the 

 diabase has been found. If such a deep source is postulated, then the 

 means by which its emanations reached the present horizon must 

 receive scrutiny. 



When attention is given to possible ore conduits and channels of 

 distribution, it is recognized that the strike-slip faults, as a rule, 

 having horizontal lengths of less than 4000 feet, and being due to hori- 

 zontal stress, probably have less vertical lengths, while the common 

 dip-slip reverse faults lie only on the limbs of the folds. The only 

 faults, therefore, which could be presumed to penetrate to the required 

 depths would be those on major tectonic lines, of which the only 

 known representative in or near the mining district is the Cobalt Lake 

 fault. There is known to be no such fault along the Peterson Lake 



