ROCKS OP THE PRE-CAMBRIAN COMPLEX 23o 



Shuswap rocks may have been produced rather beneath the mere weight of 

 superincumbent strata than by pressure of a tangential character accompanied 

 by folding, and that both these rocks and those of the Cambrian were at a 

 later date folded together." 



In the foregoing it has been implied that the gneissic and schistose 

 structures of the pre-Cambrian of Mineral ridge were developed in pre- 

 Cambrian time, and that the planes of these structures were approxi- 

 mately horizontal. On this hypothetical horizontal floor the Algonkian 

 (if present) and Lower Cambrian sediments were deposited. These are 

 in large part fine grained quartzite, limestone, and shale, suggesting quiet 

 conditions. Basal conglomerates are wanting. It may be held that if 

 the rocks described as pre-Cambrian are really so, distinct evidence of an 

 unconformity with the overlying Lower Cambrian should be observable. 

 This, however, loses weight when we consider that the Lower Cambrian 

 sediments, chiefly shale and limestone, must have been laid down in quiet 

 water and, as supposed, on a nearly horizontal floor. Under these condi- 

 tions basal conglomerates would not readily form. Moreover, the proof 

 of strong stresses having been applied to the pre-Cambrian complex re- 

 sulting in thorough gneissic and schistose structures, while the overlying 

 Cambrian shows no such evidence of stresses, certainly suggests a con- 

 siderable difference in age. 



An old eroded surface is usually an irregular surface, but on account 

 of disturbances subsequent to Lower Cambrian time, and on account of 

 the erosion of the larger part of this old eroded surface of the pre- 

 Cambrian of Mineral ridge, no satisfactory evidence was obtained as to its 

 contours. Lying on top of the pre-Cambrian of Mineral ridge are two 

 ridges composed of Lower Cambrian sediments. The even line of contact 

 of the pre-Cambrian with these Lower Cambrian beds suggests that the 

 hypothetical old eroded surface is not very irregular. 



GRANITIC QUARTZ-VEINS 



In addition to ordinary quartz veins in the pre-Cambrian, there are 

 other veins and bunches of quartz which appear to represent the acid 

 extreme of granitic dikes. Such veins usually contain a little feldspar 

 and white mica, while others to which a similar origin may be assigned 

 contain none. Assays were made of the quartz from two of these veins 

 and only one of them showed the presence of gold. No sulphides have 

 been noted in them. The quartz has often a banded structure, due, as 

 shown by the thin-sections, to crushing and subsequent recrystallization, 

 the granules of quartz being drawn out in parallel lines, so that some 

 specimens might be called quartz-gneiss. This granitic quartz is usually 



