DESERT QUEEN SHAFT. 125 



The percentage of gold may be smaller in the lower lifts, but the data are 

 not sufficient to support this idea, and a proportion similar to the average 

 (1:100) has been found in the shipments of primary sulphides from the rich 

 ores of the Montana Tonopah. 



Moreover, the rich shoots seem, under microscopic stud} 7 , to be original, 

 though the ore is largely altered that is, the ore seems to have altered essentially 

 in place, without any thorough rearrangement. This may be ascribed in part to 

 the relatively scanty supply of surface waters in this arid region. 



Some transportation, nevertheless, was inevitable, and it is probable that to 

 a minor degree the ores have been redeposited. The result has probably been 

 that values are more evenly distributed over the oxidized vein than they were 

 originally; and the vein has been enriched to some degree by the downward 

 penetration of minerals leached from the outcrop as it was eroded. 



GEOLOGY OF THE DESERT QUEEN SHAFT. 



The Desert Queen is the chief working shaft of the Belmont Company, and 

 the ores discovered in the workings from this shaft are usually referred to as 

 the Belmont ore bodies. The shaft is one of the deepest in the camp. 



INTRUSIVE NATURE OF RHYOLITE CONTACT. 



As shown on the map (PI. XVI), the Desert Queen shaft starts in the rhyolite, 

 on the southeast slope of Mount Oddie. It passes downward through this rhyolite 

 for 250 feet, below which it encounters a mass of dark-blue or brown clay, 

 containing harder residual bowlders of the later andesite. This has a thickness 

 of more than 50 feet in the shaft, and is evidently a broken and ground up 

 later andesite, altered to a clay by traversing waters. Below this water occurs 

 along a fracture. 



This zone of movement strongly resembles a fault zone. However it is to 

 be noted that the movement has affected only the andesite and not the rhyolite, 

 that the rhyolite is not noticeably decomposed, and that there are no rhyolite 

 fragments in the breccia. This indicates rather that the disturbance was caused 

 bv the intrusion of the rhyolite into the andesite. The exact attitude of the 

 rhyolite contact could not be observed, but it may be assumed to be roughly 

 parallel to the watercourse just mentioned, which strikes north and south and 

 dips east at an angle of 60 D . 



At the surface this rhyolite is in contact with the Siebert tuff lake beds 

 about 120 feet west of the shaft, as shown on the map; this contact strikes north 

 and south. Beneath the lake beds in this block lies the later andesite, as shown 

 for example in the Silver Top shaft, a short distance to the southwest. A line 



