Geologic setting of gold mineralization at the Double Mountain Prospect, Northern Adobe Range, Elko County, Nevada

Geologic and alteration mapping, rotary drilling (over 2700 m in10 holes, >50%
of intervals anomalous in gold and/or pathfinder elements), radiolarian biostratigraphy,
and exploration geochemistry (grid rock, soil, and drill cuttings) of the Double
Mountain prospect finds multiple gold anomalies within a 64 square kilometer area.
The prospect is about 100 km northeast of Elko, Nevada and 16 km east of the Jerritt
Canyon gold deposit. The gold anomalies are enclosed by larger coincident anomalies
of arsenic, mercury, antimony, vanadium, molybdenum, and zinc. The host rocks are
pervasively hydrothermally altered Paleozoic sedimentary rocks. The most intense
alteration is at intersections of northeast structures with east-west and northwest
high-angle structures and low-angle thrust faults.
The Paleozoic stratigraphy exposed in the Double Mountain area is part of the
overthrust (upper-plate) rocks of the Roberts Mountains allochthon (RMA) and consists
of quartzite, fine-grained sandstone, siltstone, and chert that can be assigned to
the stratigraphic units observed in other parts of the RMA. The most common rock
type in the Vinini Formation is a coarse grained quartzite which is locally overlain by
thinly bedded micaceous siltstone and fine-grained sandstone of the Elder Formation.
Locally, a thin, variably-colored chert, the Early Silurian Cherry Spring chert, separates
the Elder Sandstone from underlying Vinini Formation. The stratigraphically
youngest unit consists of one or more chert intervals assigned to the Slaven Chert.
Radiolarian biostratigraphic data indicate a late-Early to early Late Devonian age for
stratigraphically uppermost chert interval. Identified radiolarians include: Helenifore
laticlavium, Trilonche sp., and Ceratiokiscum sp.
Drill hole DMR-10 (90 degrees, 595 m;1.5 m sample intervals), drilled in the
southern part of the study area, penetrated 302 m of intensely altered quartzite, siltstone,
and minor chert of the Vinini Formation before intersecting silicified and decalcified
siltstone/mudstone interpreted to be autochthonous Roberts Mountain
Formation. Tertiary rocks postdate gold mineralization and include minor prevolcanic
sediments, lithic-rich surge deposits, shale, and air fall tuffs. An extensive Tertiary
crystal-rich welded rhyolite ash flow tuff, assigned to the Jarbidge Rhyolite, is the
uppermost rock unit.