Stratigraphy and structure of the Gold Creek and Charleston gold districts, Elko County, Nevada

The historic Gold Creek and Charleston gold districts are located among highly
deformed and horizontally displaced rocks northeast of Wild Horse Reservoir in
northeastern Elko County, Nevada. New stratigraphic data and structural interpretations
of the areas are based on 42 collections of fossils, and mapping at a scale of
1:24,000. A sequence composed of the following three stratigraphic units exposed in
the map areas comprises an extensive basement autochthon: (1) Proterozoic metamorphic
rocks, (2) the Proterozoic(?) to Cambrian Prospect Mountain Quartzite, and
(3) distal carbonate turbidite strata of the Cambrian to Ordovician Tennessee Mountain
Formation. Lowermost beds of the Tennessee Mountain Formation, too poorly
exposed to map separately, constitute the lithic and temporal equivalent of the Cambrian
Pioche Shale. Outside the map areas, the autochthon includes rocks of Ordovician,
Mississippian, and less certainly, Pennsylvanian and Permian strata. The
autochthonous strata strike generally northeast and dip very steeply, younging to the
northwest. Overlying these steeply dipping strata in both the Gold Creek and
Charleston districts is a chaotic assemblage of imbricated tectonic plates separated
from the autochthon and from each other by low-angle faults. Each of the allochthonous
plates is composed of one or another of the following stratigraphic units or
sequences: (1) the Prospect Mountain Quartzite, (2) The Tennessee Mountain Formation,
(3) Mississippian and Pennsylvanian strata of the Upper Devonian to Permian
Havallah sequence (also locally termed “Schoonover Formation”), (4) the Upper
Pennsylvanian to Permian Sunflower Formation, and (5) Upper Eocene volcanic and
sedimentary rocks. Based on their contrasting internal stratigraphic content and fold
orientations, the principal allochthonous plates were displaced from distinctly different
locations. The steep dips in the autochthon are younger than Mississippian and
probably younger than Permian. The low-angle faults are younger than Permian and
at least one of them is latest Eocene or younger. The oldest post-tectonic formation in
the mapped areas is the Miocene Jarbidge Rhyolite. Whether the low-angle faults are
the result of contraction or of extension is locally indeterminate. Within the gold districts,
the autochthon and some of the overlying allochthonous plates were intruded
by Jurassic plutons of grano-dioritic to monzonitic composition. Gold deposits were
discovered in the 1870s and the districts have been explored sporadically to the 1990s.
According to published records, most of the production was from placers but some
gold and other metals reportedly were mined from the Jurassic plutons.