Summary:
Deposit Geology
Four gold deposits on the Fremont Property are described. Two of the four deposits, namely the Pine Tree-Josephine and Queen Specimen , are included in the current Mineral Resource Estimate. The additional two deposits, Crown Pillar and Chicken Gulch, are not included in the current Mineral Resource Estimate. However, with additional drilling, they could potentially be included in a future updated Mineral Resource Estimate, and therefore are described farther below.
Deposit Types
The gold deposits of the Fremont Property are classified as orogenic mesothermal gold deposits (Sillitoe, 2008; Goldfarb and Groves, 2015; Groves and Santosh, 2016). This gold deposit type is hosted in metamorphosed volcanic and sedimentary rocks and associated with major terrane-bounding fault zones in subduction-related geodynamic and geotectonic settings.
Gold mineralization in orogenic gold deposits is structurally controlled and hosted in altered quartz veins, vein networks, and wall rock adjacent to and along major regional-scale faults. The veins consist mainly of quartz and carbonate, with smaller amounts of chlorite, scheelite, tourmaline, and native gold. Pyrite, chalcopyrite and pyrrhotite comprise <10% of the veins. Mineralization is generally gold-rich with a gold to silver ratio of 5:1 to 10:1 and high contents of sulphur, arsenic, tellurium, tungsten, boron and molybdenum, along with low contents of lead and zinc.
Mineralization
Three main styles of gold mineralization are present at the Pine Tree-Josephine Deposit and generally throughout the 4 km mineralized trend:
1. quartz hosted;
2. sulphide replacement; and
3. oxide cap mineralization.
The quartz-hosted mineralization, represented primarily by the footwall and hanging wall veins and stockwork vein arrays locally in the footwall and hanging wall, consists primarily of free gold in quartz. In historical mining (SLR, 2021), higher-grades were present in large quartz veins where cut by late-stage quartz veins, defining mineralized shoots. The mineralized shoots were generally short in strike length, and persistent at depth.
The sulphide replacement mineralization occurs mainly in the tectonic melange between the footwall and hanging wall veins. According to SLR (2021), the host meta-sedimentary, volcanic and ultramafic rocks are intensely altered to ankerite, sericite, albite, quartz, mariposite, and 3% to 4% pyrite ± arsenopyrite ± chalcopyrite. Gold occurs intergrown with the pyrite and interstitial to the quartz. Mineralized schists and tectonite pods contain pyrite and ankerite and host quartz-ankerite veinlets.
According to Burgoyne (2013), historical petrographic thin-section studies report the presence of gold mineralogically as native gold and electrum. Gold grains within pyrite grains vary from 0.03 mm to 0.05 mm in size.
The oxide gold mineralization occurs as a thin cap on the upper portions of the gold deposits. In the order of one-sixth to one-seventh of the upper parts of the deposits are variably oxidized and potentially amenable to cyanide heap leaching. Generally, the oxide zone varies from approximately 0.5 m to a maximum of 56 m (185 ft) below surface.
Structurally, the bulk of the gold mineralization along the 4 km Pine Tree-Josephine mineralized trend is interpreted to be associated with fault-fill veins, breccia veins, and extensional veins formed during various increments of D1 brittle-ductile reverse dip-slip movement (shearing) along the Melones Fault Zone (SRK, 2014).
Other Gold Deposits Of Interest
The Fremont Property gold deposits not included in the current Mineral Resource Estimates are the Chicken Gulch and Crown Point Deposits. These two deposits are both located along the 4 km Pine Tree-Josephine trend; however, there are insufficient drilling data to support Mineral Resource estimation. With further drilling, however, these two deposits could perhaps be included in future updated Mineral Resource Estimates, and therefore are briefly described below.
Chicken Gulch Deposit
The Chicken Gulch Deposit is a wedge-shaped, altered and mineralized zone that extends approximately 914 m (3,000 ft) in length and 107 m to 122 m (350 ft to 400 ft) in width at the south limit of the Fremont Property. The Deposit narrows irregularly along trend towards the north and ultimately coalesces with Pine Tree-Josephine Deposit. Quartz veins occur along the hanging wall and footwall of the altered zone for much of its length. Historical development consisted only of surface cuts, some shallow shafts, and an adit driven from the north bank of Chicken Gulch. Near-surface gold mineralization occurs in the oxide zone and deeper mineralization in the underlying sulphide zone.
Crown Point Deposit
The Crown Point Deposit is located north along strike from the Pine Tree-Josephine Deposit. The Crown Point Deposit was explored by a number of short adits, most of which are now collapsed. Crown Point is geologically similar to the Pine Tree-Josephine and Chicken Gulch Deposits, with serpentinite and Mariposa Formation rocks in the hanging wall.
According to SRK (2014), an approximately 10 m-wide shear zone within the sedimentary sequence at Crown Point defines the footwall margin of the Melones Fault Zone in this area. This shear zone is oriented at 020°/52°, and contains a stretching lineation oriented at 35°/071°. Shear sense indicators here indicate dextral-reverse oblique-slip movement. The Crown Point Shear Zone is characterized by four features:
1. a hanging wall quartz vein stockwork in thick bedded, medium-grained sandstone;
2. a 1 m-wide zone of strong chlorite alteration at the hanging wall margin;
3. shear zone parallel quartz veins within fine-grained sedimentary rocks in the core of the shear zone; and
4. a 50 cm-wide quartz vein breccia at the footwall margin.
Significant quartz vein development was not observed in the footwall rocks to the Crown Point Shear Zone.