Resistivity structure across the Humboldt River basin, north-central Nevada

Magnetotelluric data collected along five profiles show deep
resistivity structures beneath the Battle Mountain-Eureka and
Carlin gold trends in north-central Nevada, which appear
consistent with tectonic breaks in the crust that possibly served
as channels for hydrothermal fluids. It seems likely that gold
deposits along these linear trends were, therefore, controlled by
deep regional crustal fault systems.
Two-dimensional resistivity modeling of the magnetotelluric
data generally show resistive (30 to 1,000 ohm-m) crustal blocks
broken by sub-vertical, two-dimensional, conductive (1 to 10 ohmm)
zones that are indicative of large-scale crustal fault zones.
These inferred fault zones are regional in scale, trend
northeast-southwest, north-south, and northwest-southeast, and
extend to mid-crustal (20 km) depths. The conductors are about
2- to 15-km wide, extend from about 1 to 4 km below the surface
to about 20 km depth, and show two-dimensional electrical
structure. By connecting the locations of similar trending
conductors together, individual regional crustal fault zones
within the upper crust can be inferred that range from about 4-
to 10-km wide and about 30- to 150-km long. One of these crustal
fault zones coincides with the Battle Mountain-Eureka mineral
trend. The interpreted electrical property sections also show
regional changes in the resistive crust from south to north.
Most of the subsurface in the upper 20 km beneath Reese River
Valley and southern Boulder Valley are underlain by rock that is
generally more conductive than the subsurface beneath Kelly Creek
Basin and northern Boulder Valley. This suggests that either
elevated-temperature or high-salinity fluids, alteration, or
carbonaceous rocks are more pervasive in the more conductive area
(Battle Mountain Heat-Flow High), which implies that the crust
beneath these valleys is either more fractured or has more
carbonaceous rocks than in the area surveyed along the 41st
parallel.