238 H. W. TURNER GEOLOGY OF THE SILVER PEAK QUADRANGLE 



Number 208 is from 1.1 kilometers northwest of the Silver Peak benchmark. 

 It is a multiple dike along a dike of white granite which is broken up and in- 

 truded by the greenstone. The latter sends branches in between layers of the 

 white granite. These branches show salbands. The rock is composed chiefly 

 of green-brown amphibole in idiomorphic needless and lime-soda feldspar 

 which is too altered to determine its exact nature. 



Number 222 is from 2.5 kilometers north of the Silver Peak benchmark. 

 It is from a vertical dike, one of a series nearly in a line that cuts across the 

 basement complex in a direction about north 75 degrees west, for a distance of 

 nearly 2 miles. It is composed chiefly of green hornblende and may be desig- 

 nated an hornblendite. 



The diorite dikes were supposed by Professor J. E. Clayton to be older 

 than the quartz veins, but as they cut across the veins, this is evidently 

 an error. They are more abundant near the quartz veins in which the 

 silver values predominate, but they do not occur along all of the silver 

 veins and are found along some of the gold veins. They do not appear, 

 therefore, to have exerted any influence on the kind of ore found in th-d 

 veins, and inasmuch as they are later than the veins, it is improbable that 

 they have exerted any influence whatever on the ore deposition. 



Paleozoic Sedimentary Series 

 algonkian rocks 



Mr CD. Walcott has established a lower limit for the Cambrian rocks, 

 which if applied in this district will place some of the dolomites and 

 quartzites of the Silver Peak quadrangle in the Algonkian. He writes : ie 



"At present I draw the basal line of the Cambrian in Utah and Nevada at 

 the bottom of the arenaceous shale, carrying the Olenellus fauna. This refers 

 the quartzite and siliceous shales of the Wasatch and similar sections, in- 

 cluding that of the Eureka district, and that of the Highland range of Nevada 

 to the Algonkian Period (Era)." 



On this basis the dolomite, quartzite, and the green knotted schists 

 underlying the Olenellus zone north of the Clayton valley may be called 

 Algonkian. This might apply as well to some of the quartzite and 

 quartz-schist immediately west of the village of Silver Peak, and to the 

 basal dolomite generally of Mineral ridge, as well to some similar rocks 

 south of Cow camp. ~No fossils have been found in these basal dolomites 

 and quartzites. On the geological map these basal beds are placed with 

 the Lower Cambrian. They are referred to here more especially to call 

 attention to the fact that the series underlies the fossiliferous Cambrian 

 rather than to insist on the Algonkian age of the rocks, as it is quite 

 possible that they represent the base of the Cambrian. 



THE PALEOZOIC ERA 



The Paleozoic fossiliferous rocks of the Silver Peak quadrangle are 



"American Journal of Science, vol. xxxvii, 1889, pp. 374-392. 



