Summary:
The Project is underlain primarily by a generally north trending sequence of Permian to Mississippian sedimentary rocks composed of siltstones, mudstones, sandstones, conglomerates and limestones, subdivided into several units or formations.
A dolomite hydrothermal alteration overprint has been interpreted within the Project area, based on geochemical drill hole data from drill holes that variably penetrate into the grey–brown siltstone and black mudstone sequences, and vanadium-rich zones.
Vanadium mineralization is stratigraphically controlled, and appears to follow the strike and dip of the host lithology, near the contact between an overlying grey–brown siltstone and the underlying brown to black mudstone unit of the Devonian-age Woodruff Formation. The mineralized zones form as stratigraphic subunits or beds within the Woodruff Formation mudstone, hosting elevated concentrations of vanadium in the form of vanadium pentoxide (V2O5).
The most persistent, thickest, and highest-grade vanadium unit lies in the brown–black mudstone unit and averages approximately 115 ft (35 m) thick, striking north–south over 6,000 ft (1,800 m) of length and 2,000 ft (600 m) wide in the east–west direction.
The mineralization is locally exposed at surface at both the Central and South Zones, but mostly at a shallow depth less than 200 feet (60 m) from surface. Above and below the high-grade zone are other vanadium zones within the brown–black mudstone unit that are generally less persistent laterally, which are of moderate grade (0.2–0.5% V2O5) but are thinner (30–75 ft thick).
There is a relatively persistent, flat-lying, high-grade vanadium-enriched bed averaging 115 ft thick within the upper grey–brown mudstone unit to the west of the Central Zone. Other vanadium zones within the grey–brown mudstone are generally less persistent laterally, of moderate grade (0.2–0.4% V2O5), and are thinner (30–60 ft thick).
Mineralogical studies by First Vanadium and UCC show the vanadium is present in the form of metahewettite (CaV6O16•3(H2O) and corvusite ((Na,Ca,K)V8O20•4(H2O), which are finely and evenly disseminated throughout the host lithologies with grain size from a few micrometers to almost 100 µm, averaging about 10–20 µm.
Other vanadium minerals identified in the deposit in rare, very rare or trace amounts were montroseite ((V3+,Fe3+)O(OH))–goethite, pascoite (Ca3(V10O28)•17H2O), steigerite (Al(VO4)•3H2O), tangeite (CaCu(VO4)(OH)), tyuyamunite (Ca(UO2)2(VO4)2•5–8H2O) and vesignieite (BaCu3(VO4)2(OH)2).
The Carlin Vanadium deposit is interpreted to be a syngenetic-type vanadium deposit. The vanadium is believed to have originally formed in a deep, restricted marine basin associated with the depositional environment of the western assemblage lithologies. As the marine basin filled, sub- basins formed. Organisms likely in the form of algae, bloomed on the shallow flanks of the sub- basins. As these organisms died, they contributed to carbon input into the basin. It is interpreted that the vanadium was concentrated into laterally relatively continuous mudstone/siltstone units by precipitation, absorption aided by carbon accumulation and evaporation processes as the restricted basin filled, evaporated, and concentrated the seawater into salts.
The mineral deposits along the Carlin Trend form a suite of deposits known as Carlintype, or sediment-hosted, low-grade disseminated gold deposits. The Carlin Trend hosts the largest concentration of gold deposits in North America. The preferential host rocks are autochthonous carbonate assemblage rocks that are now preserved in uplifted tectonic windows. Within specific deposits, Cretaceous and Tertiary dike swarms and a Jurassic-aged granodiorite stock (Goldstrike stock) may constitute as much as 15% of the mineralized material. Host rocks are most commonly thinly-bedded silty or argillaceous carbonaceous limestone or dolomite, commonly with carbonaceous shale/mudstone. Although less mineralized, non-carbonate siliciclastic and rare metavolcanic rocks can locally host gold that reaches economic grades. Felsic plutons and dikes may also be mineralized at some deposits. Deposits typically have a tabular shape, are stratigraphically and structurally controlled, are localized at contacts between contrasting lithologies or structural intersections, but can also be discordant or breccia-related.
Mineralization consists primarily of micrometer-sized gold and sulphide grains disseminated in zones of siliciclastic and decarbonated calcareous rocks and are commonly associated jasperoids. Major ore minerals include native gold, pyrite, arsenopyrite, stibnite, realgar, orpiment, cinnabar, fluorite, barite, and rare thallium minerals. Gangue minerals typically comprise fine-grained quartz, barite, clay minerals, carbonaceous matter, and late-stage calcite veins.