Wood tin in the Tertiary rhyolites of northern Nevada

Adolph Knopf
1916 Economic Geology and The Bulletin of the Society of Economic Geologists  
Tin ore has recently been found in northern Lander County, Nev. The stanniferous mineral is wood tin, occurring in narrow veinlets, traversing a series of rhyolite lavas of middle Tertiary age. The wood tin of these deposits is the first recorded occurrence of this mineral in place in the United States. To point ou• the hydrothermal origin of the deposits, the association of an unusual number of varieties of silica with the wood tin, and certain features of colloidal deposition that are
more » ... ly exemplified by the deposits, is the purpose of this paper. 2 THE RHYOLITE COUNTRY ROCK. The rhyolites that enclose the veins are markedly porphyritic, the phenocrysts forming nearly half the bulk of the rocks. Quartz and sanidine dominate, and oligoclase (Ab70Ana0) occurs sporadically. Ferromagnesian minerals were rare and apparently consisted in the main of hornblende, now pseudomorphously altered to hematite. The rhyolites are rather porous and tithophysal; they commonly show flow-layering and in places are flowbrecciated; in short, they bear abundant evidence that they consist of a superposed succession of lava flows. According to W. H. Emmons a they a•e the oldest Tertiary lavas in this part of Nevada and their eruption probably began early in Miocene time. The following par'tial analysis sho•vs clearly the siliceous, alkalic character of the rhyolites:
doi:10.2113/gsecongeo.11.7.652 fatcat:uzwwrwa4hbfddl6hghw2cj6uty