Summary:
Mineralization
Gold-silver mineralisation at the Santa Fe Project is controlled by various interplays of faults (which provided fluid conduits), lithological contrasts (rheological and chemical), intrusive contacts, and structural complexities such as fault intersections and fault jogs. As such, the geometries of individual deposits are variable.
Santa Fe Deposit (Historically Mined)
The Santa Fe deposit is hosted within the Santa Fe Fault Zone in limestone of the Luning Formation. The deposit occurs at the intersection of the Santa Fe Fault Zone and the Calvada fault where the strike of the Santa Fe Fault Zone deflects from northwest to west-northwest. This change in orientation may be controlled by the Todd Mountain stock which seemingly acted as a relatively rigid block and between the contact of the TRl4 and underlying TRl2 and TRl3. Two styles of mineralisation occur at Santa Fe deposit – narrow zones of steely-dipping gold and antimony-rich jasperoid which occurs along faults and dyke contacts, and pyrite-rich siliceous limestone breccia.
Slab Deposit (Historically Mined)
The Calvada West deposit (also known as Slab) occurs in the central part of the property and was (i.e., pre-mining) marked at surface by a north-northeast to north-trending silicified ridge comprised of dark sulfide-bearing jasperoid that replaced basement rocks and exposed Luning limestone. The location of the deposit is controlled by an interplay of the Calvada fault, a subsidiary north to north-northeast fault, and the unconformity between the Luning formation limestone and overlying Tertiary Lavas of the Giroux Valley formation. Post-mineral faulting has also introduced minor offset within portions of the deposit. The Slab deposit is a shallowly dipping antiform that plunges to the northeast at 010°. The Slab deposit consists of three zones: an upper, middle, and lower zones.
Calvada Central Target
The Calvada Central target occurs along the east-west trending Calvada fault midway between Calvada West and East. Mineralisation occurs within the Calvada fault zone and in the Luning limestone in jasperoids focused along the unconformity with the overlying Tertiary Lavas of the Giroux Valley. The Calvada Central target occurs as two jasperoid lenses of variable thickness. The Hangingwall jasperoid lens occurs nearthe unconformity and is generally thicker and higher grade than the footwall lens. The Calvada Central target occurs as oxide based on ratios of cyanide leach to fire assay ratios and logged sulphide abundance.
Calvada East Deposit (historically mined)
Calvada East is an east-west trending, steeply dipping arcuate zone marked by gold-bearing dark jasperoid within proximity to the Calvada fault. The hanging-wall is comprised of the Lavas of the Giroux Valley, which overlies or is in contact with the mineralised Triassic Luning formation limestone. Mineralisation occurs near the contact of the two units along the Calvada fault zone. The footwall of the Calvada East deposit consists ofstrong clay-altered quartz monzonite intrusive rocks analogous to the Cretaceous Todd Mountain intrusive suite. The Calvada East deposit measures approximately 500 m along strike and ranges from 3 m to 50 m thickness and averages 20 m in thickness. The Calvada East Deposit occurs as two separate jasperoid lenses that intersect within the central portion of the Calvada East deposit where the thickest portions of the deposit have been historically mined. The deepest drilling at Calvada East has encountered transitional oxide and non-oxide mineralisation based on ratios of cyanide leach to fire assay ratios and logged sulphide abundance.
York Deposit (historically mined)
The York deposit occurs within the Triassic Luning formation that has been locally recrystalised to marble. The historically mined portions of the York deposit occur along a northeast striking, steeply dipping faultsthat is interpreted to be an offset portion of the Calvada fault. The York deposit is tabular and dips shallowly (35°) to the northeast (040°). Thicker portions of the York Deposit occur in proximity to the faults. The York deposit occurs as oxide based on ratios of cyanide leach to fire assay ratios and logged sulphide abundance.
Pinnacle Target
The Pinnacle target is a gold in soil geochemical anomaly overlying a northwest trending fault zone occurring in the Mickey Pass Tuff. Rocks within this target are siliceous with oxidized pyrite veinlets and argillized breccia; samples have returned anomalous gold values (Victoria Gold Corp., 2012 and Gesualdo and Stock, 2023). A magnetic low area that extends from the Santa Fe pit toward the Pinnacle target is interpreted as a continuation of the Santa Fe fault and near-surface Luning limestone.
Deposit Type
Gold-silver deposits of the Walker Lane – including those of the Santa Fe Project – fall into the well-known class of epithermal gold-silver deposits (description herein summarized from Hedenquist et al., 2000; John et al., 2018). These deposits form in the upper ~1.5 km of the crust from magmatic hydrothermal systems driven by subvolcanic feederintrusions. Modern active geothermal systems are their present-day analogues. As well as enrichment of the precious metals, Zn, Pb, Cu, Hg, Sb and S typically form subeconomic deposits in these systems but are useful pathfinders to gold and silver. The magmatism in most epithermal districts is subduction-related calc-alkaline and ranges from basaltic to rhyolitic in composition. The epithermal deposits of the Walker Lane mineral belt formed during Cenozoic arc magmatism that resulted from subduction of the Farallon plate beneath North America.
Both the associated volcanism and the hydrothermal systems that form epithermal deposits are typically strongly structurally controlled. Deposit styles vary considerably and include vein, breccia, stockwork, disseminated and replacement, with many individual deposits or districts having multiple styles. Interaction between the causative hydrothermal system and paleo-water tables, as well as chemically and rheologically distinct host rocks, are responsible for much of the observed variation. For example, vein-type deposits with bonanza-grade precious metals may form within a feeder conduit fault while, at the same time, a low-grade disseminated style deposit formed adjacent to the fault within permeable and/or chemically reactive beds
Although magmatic arcs throughout the world host epithermal deposits, those found in the Walker Lane benefit from the deep weathering profile characteristic of region. Oxidation of primary precious metal-bearing minerals, such as pyrite, liberate gold and makes ore processing significantly cheaper. Gold and silver from many epithermal deposits of the Walker Lane (including Santa Fe) have been extracted using low-cost heap leach techniques meaning grade and tonnage thresholds are generally lower for oxidized deposits compared with unoxidized or hypogene deposits.
Copper skarn deposits within Mesozoic basement rocks are a secondary deposit target that has not been widely evaluated at the Santa Fe Project. Skarn deposits are coarse-grained contact metamorphic rocks comprised of calc-silicate minerals that form where a granitoid pluton has emplaced within limestone or other carbonate-rich sedimentary rocks (Hammarstrom et al., 1995). Skarns can be barren or host significant base metals or gold. Although skarns have not been reported at the Santa Fe Project, the New York Canyon project hosts several oxide and sulfide copper skarn deposits 10 km south of the Santa Fe pit. Given that the Mesozoic Todd Mountain Granite contact with Luning limestone is exposed south of the Santa Fe pit, skarn potential should not be discounted. This setting is prospective and has not been widely evaluated.