We have collected about 150 magnetotelluric (MT) soundings in 
northeastern Nevada in the region of the Ruby Mountains metamorphic 
core complex uplift and southern Carlin mineral trend, in an effort to 
illuminate controls on core complex evolution and deposition of world-
class gold deposits. The region has experienced a broad range of 
tectonic events including several periods of compressional and 
extensional deformation, which have contributed to the total expression 
of electrical resistivity. Most of the soundings are in three east-west 
profiles across increasing degrees of core uplift to the north (Bald 
Mountain, Harrison Pass and Secret Pass latitudes). Two shorter lines 
cross a prominent east-west structure to the north of the northern 
profile. MT impedance tensor and vertical magnetic field rotations 
imply a N-NNE average regional geoelectric strike, similar to surface 
geologic trends. Model resistivity cross sections were derived using a 
2-D inversion algorithm, which damps departures of model parameters 
from an a priori structure, emphasizing the transverse magnetic (TM) 
mode and vertical magnetic field data. Geological interpretation of the 
resistivity combines previous seismic, potential field and isotope 
models, structural and petrological models for regional compression and 
extension, and detailed structural/stratigraphic interpretations 
incorporating drilling for petroleum and mineral exploration. To first 
order, the resistivity structure is one of a moderately conductive, 
Phanerozoic sedimentary section fundamentally disrupted by intrusion 
and uplift of resistive crystalline rocks. Late Devonian and early 
Mississippian shales of the Pilot and Chainman Formations together form 
an important conductive marker sequence in the stratigraphy and show 
pronounced increases in conductance (conductivity-thickness product) 
from east to west. These increases in conductance are attributed to 
graphitization caused by Elko-Sevier era compressional shear 
deformation and possibly by intrusive heating. The resistive 
crystalline central massifs adjoin the host stratigraphy across 
crustal-scale, subvertical fault zones. These zones provide electric 
current pathways to the lower crust for heterogeneous, upper crustal 
induced current flow. Resistive core complex crust may be steeply 
bounded under the middle of the neighboring grabens and not deepen at a 
shallow angle to arbitrary distances to the west. The numerous crustal 
breaks imaged with MT may contribute to the low effective elastic 
thickness estimated regionally for the Great Basin and exemplify the 
mid-crustal, steeply dipping slip zones in which major earthquakes 
nucleate. An east-west oriented conductor in the crystalline upper 
crust spans the East Humboldt Range and northern Ruby Mountains. The 
conductor may be related to an inferred Archean-Proterozoic suture or 
nearby graphitic metasediments, with possible alteration by middle 
Tertiary magmatic activity. Lower crustal resistivity everywhere under 
the profiles is low and appears quasi one-dimensional. It is consistent 
with a low rock porosity (<1 vol. %) containing hypersaline brines and 
possible water-undersaturated crustal melts, residual to the mostly 
Miocene regional extension. The resistivity expression of the southern 
Carlin Trend in the Pinon Range is not a simple lineament but rather a 
family of structures attributed to Eocene intrusion, stratal 
deformation and graphitization. Substantial reactivation or 
overprinting by core complex uplift or extensional events seems likely. 
We concur with others that the Carlin trend may result in part from 
overlap of the large Eocene Northeast Nevada Volcanic Field with 
Precambrian-Paleozoic deep-water clastic source rocks thickening 
abruptly to the west of the Pinon Range, and projections to the north-
northwest.