The Griffin Mine: Contraction, Extension, and Gold Mineralization in the White Pine Range, Nevada

A recent addition to the list of precious-metal mines in the
White Pine Range of eastern Nevada, the Griffon mine is in the
east-central part of the range, approximately 19 kilometers (12
miles) south of the Treasure Hill silver district and 13 kilometers (8
miles) east of the Green Springs gold mine. An area with no historic
production or exploration activity prior to the late 1980s, the
Griffon mine consists of two distinct, sediment-hosted gold
deposits of roughly equal size with centers approximately 400
meters (1300 ft.) apart. Alta Gold Company produced 3.0 million
tons of ore with an average grade of 0.03 ounce per ton from these
two deposits between 1997 and 1999. Mineralized strata in both
deposits consist of Mississippian siltstone, shale, and silty limestone
that correlate with the lower Chainman Formation and upper
Joana Limestone.
Surface mapping and drill data determined the following
sequence of geologic events at Griffon, starting after the deposition
of Permian strata: (1) A minor event of normal faulting that formed
WNW-striking faults. (2) Mesozoic contraction that formed northtrending
open folds and possible local thrust faults. (3) Low-angle
normal faulting that juxtaposed Mississippian strata over Devonian
through Mississippian strata. (4) Gold mineralization that occurred
primarily within the hangingwall of the low-angle normal fault(s).
(5) Aminor normal faulting event that formed NE-striking faults. (6)
Normal faulting that produced ENE-striking faults with variable displacements
as much as several hundred feet. (7) A period of faulting
that formed (or possibly reactivated) several faults with strikes
between N and NW which display normal and/or strike-slip displacement.
Such a fault separates the two deposits. (8) Low-angle
normal faulting along the Blackrock Fault, a major structure in the
southern part of the range. Cross-cutting relationships indicate that
this fault was active between 31.3 and 14.3 Ma.
Numerous similarities exist between the Griffon and Green
Springs deposits. These include: (1) Elevated levels of antimony,
arsenic and mercury associated with gold ore, although Griffon ore
contains higher zinc and lower silver concentrations than Green
Springs. (2) The mineralized zone occurs along the contact of
Chainman Formation and Joana Limestone which is locally interpreted
to be a low-angle normal fault, and (3) A probable Late
CretaceousÐmid-Oligocene age of mineralization. It is unclear if
these epithermal-style gold deposits are genetically linked to the
Late Cretaceous intrusion-related silver and base metal deposits at
Treasure Hill and Mt. Hamilton to the north.