162 GEOLOGY OF TONOPAH MINING DISTRICT, NEVADA. 



nearly parallel, as it happens, with the strike of the vein. Blocks lying in zones 

 with this general trend have been systematically elevated above adjacent parallel 

 zones lying to the northwest. 



The vein, dip as a factor in th problem. In the case of the faulting on the 

 Wandering Boy 300-foot level, the problem takes on an added complexity, since the 

 available test of faulting is not the relative position of the displaced blocks, but rather 

 the position of the vein, whose plane is oblique to any of the planes of the fault blocks, 

 and whose present position is what we seek ultimately to understand. The strike of 

 the vein being nearly parallel with the trend of equal displacement, it results that if 

 the dip is toward the direction of resultant equal downthrow, then the two factors of 

 lowering the vein will be added and the fragments of the vein will gain depth faster 

 than the inclosing rock blocks. If, on the other hand, the dip is against the down- 

 throw, two factors of lowering the vein will be set off against each other. The vein 

 then will gain depth more slowly than the inclosing rock blocks, if the faulting has 

 a greater effect than the dip; will continue on a general horizontal plane, if the 

 faulting has an effect about equivalent to that of the dip; or will ascend, in spite of 

 the downfaulting, if the latter be sufficiently slight to have its effect overbalanced 

 by the dip. In the Wandering Boy 300-foot level, we have, as may be seen from 

 the sections, the second of these conditions. The dip is opposite to the downthrow, 

 and the angle of dip, the displacement, and the spacing of the faults are fortuitously 

 such (for a distance at least) that the one offsets the other, and the vein continues in 

 a horizontal zone. This explains why the long east and south drifts and the short 

 east crosscut from the south drift all encounter blocks of apparently the same vein; 

 and it follows that other blocks of the vein probably exist on this same level in 

 the angle between the two main drifts, and beyond the explored area as far as this 

 peculiar intersecting faulting and the balance of dip and displacement is maintained. 



CORRELATION OK VEINS IN FRACTION AND IN WANDERING BOY. 



PI. XXI, p. 140, shows the vein and faults of the corresponding 300-foot levels of 

 the Fraction and the Wandering Boy, together with the estimated position of the lines 

 of main faulting of both the Wandering Boy and the Fraction faults. It is here seen 

 that the northeast faults in the Wandering Boy, which form the majority of those 

 faults classed together, in describing the cross faulting on the 300-foot level, as north- 

 south faults, are parallel in strike, dip, and direction of displacement, with the chief 

 set of faults in the Fraction, and in strike at least with the main Fraction fault as 

 determined on the surface. These minor faults involve a movement, as seen on a 

 horizontal plane, to the north on the west side; as seen on a vertical section, down- 

 ward on the west side. The real movement has probably been a compound of these 

 two, as studied out in the Fraction workings. Along the main fault plane, then (if, 

 indeed, there is one, and the displacement is not rather distributed over many par- 



