Silent Canyon Volcanic Center, Nye County, Nevada
A late Miocene (13 to 15 m.y.) volcanic center is located on eastern Pahute Mesa near lat 37° 18′ N., long 116°20′ E., Nevada. Rocks of the center are predominantly comendites and subordinately trachytic soda rhyolite and trachyte. The distinctive and unusual mineralogy and trace- and major-element chemistry of these peralkaline rocks indicate that they are closely related genetically and allows them to be distinguished readily from rocks of other centers.
Activity began with emplacement of numerous lava flows, domes, and dikes over an area of at least 450 sq miles. Most were erupted in the general area of later caldera collapse, but some vents were 15 to 20 miles from the caldera’s midpoint. Two compound ash-flow sheets — the Tub Spring and overlying Grouse Canyon members of the Belted Range Tuff — were then erupted. The more voluminous Grouse Canyon covered 3000 sq miles and had an original volume of about 50 cu miles.
The Silent Canyon caldera formed during and/or just after eruption of the Belted Range Tuff. Only the eastern third of the caldera is exposed or reflected as steep initial dips in overlying tuffs. That the caldera is the source of the Belted Range Tuff is shown by: (1) facies changes in the Grouse Canyon Member, (2) thickness variations in underlying bedded tuffs, (3) presence of one Grouse Canyon unit and of thick post-Grouse Canyon tuffs and lavas only near the caldera, (4) occurrence of an arc of small welded-tuff vents outside and concentric with the caldera, and (5) other field evidence. The location is consistent with the regional distribution of the Belted Range Tuff.