proceedings: geological society 107 



however, to revive the name Poikilitic, but simply to retain the name 

 Triassic, extended downward to include the new, reduced, Permian 

 series. It will be seen that the new scheme avoids the difficulty in vari- 

 ous regions of distinguishing between Permian and Carboniferous, 

 resulting in the hybrid name Permo-Carboniferous, since all such strata 

 fall within the Carboniferous by virtue of the establishment of the base 

 of the Permian at a higher horizon. 



The bonanza of National, Nevada: Waldemar Lindgben. This 

 paper gave the preliminary results of a reconnaissance examination in 

 the vicinity of the National mining camp, which is remarkable for the 

 richness of the gold ore in its principal mine. 



The northern end of the Santa Rosa Range, from the Oregon line for 

 almost sixteen miles south to Canyon Creek, is made up of a succession 

 of basalt flows, interbedded with tuffs. Some of these flows are scoria- 

 ceous, others massive; they are well exposed north of Eight-Mile Creek, 

 where the whole series, over 2000 feet in thickness, dips east at gentle 

 angles. They form part of the great volcanic area of the Columbia 

 River lavas ar>i extend far to the north, east and west of National. 

 They were erupted in early Tertiary time, a time of intense volcanic 

 activity all over the Cordilleran region. 



In the earlier portion of this epoch of vulcanism the lavas in the Na- 

 tional district were basaltic in character. At a later time rhyolites were 

 poured out, and at the same time dikes and masses of rhyolite and obsid- 

 ian, generally trending north and south, forced their way up thru the 

 basalts and tuff beds, in places disturbing them greatly. Big blocks 

 of basalt are sometimes imbedded in the rhyolite. A third and later 

 intrusion was of a dark, fine-grained rock provisionally called an andesite. 

 It is of importance because of the ore bodies that it contains. Still 

 later volcanic activity produced successive basalt flows covering the 

 rhyolites, and basalt dikes cutting those of rhyolite. 



i The formation of mineral veins followed the eruptions of rhyolite and 

 andesite. Shortly after these eruptions fissures trending north and 

 south were opened, mainly along the rhyolite dikes, sometimes also 

 breaking into the basalt flows and the tuffs. The fissures are generally 

 small, rarely over a few feet in width, and commonly much less. The 

 fissure filling is mainly quartz, with drusy structure, and the character- 

 istic combination of metals is antimony (stibnite), iron (pyrite or mar- 

 casite) gold and silver. Lead, copper and zinc are generally absent. 

 Oinnabar has been observed at a few places. The veins thruout bear 

 evidence of having been deposited by hot, ascending springs at a moder- 

 ate depth below the surface. The majority of the veins so far described 

 are clearly dependent upon the rhyolite eruptions; they sometimes 

 carry considerable amounts of stibnite and the silver values usually 

 prevail over those of gold. None of the veins of the type so far described 

 has as yet yielded any considerable amount of shipping ore. The 

 case of the National vein is somewhat different. It is mainly con- 

 tained in an andesitic rock but it also cuts into basalt and rhyolite. 

 Tho its ore yields some antimony (both as stibnite and ruby silver) the 



