Summary:
The gold deposits of the Fremont Property are classified as orogenic catathermal gold deposits. This gold deposit type is hosted in metamorphosed volcanic and sedimentary rocks and associated with major terranebounding fault zones in subduction-related geodynamic and geotectonic settings.
Gold mineralization in orogenic gold deposits isstructurally 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, mariposite, scheelite, tourmaline, and native gold. Pyrite, chalcopyrite and pyrrhotite comprise <10% of the veins. Mineralization is generally gold-rich with a gold to silverratio of 5:1 to 10:1 and high contents of sulphur, arsenic, tellurium, tungsten, boron and molybdenum are present, along with low contents of lead and zinc.
Vein strike and dip extents range from hundreds to thousands of meters, either singly or, more typically, in complex vein networks. Veins are hosted in a wide variety of volcanic, sedimentary, intrusive and metamorphic rock types. The veins generally occur as systems of parallel or acutely intersecting veins, ranging in dip from 25° to 60°. Gold mineralization occurs as shoots with considerable vertical extent relative to their horizontal extent, that are generally found in ribboned vein structures, commonly in the hanging wall and (or) footwall of barren or low grade “bull” quartz veins.
Despite their significant vertical depth extent of origin, (commonly >10 km), orogenic gold deposits can lack clear vertical mineral zonation. Wall rock alteration haloes are zoned and consist of listwaenitic alteration (carbonatization, sericitization, talc and pyritization-associated alteration mineral assemblages). Alteration halo dimensions vary with the composition of the host lithologies and usually envelope entire deposits in mafic and ultramafic rocks.
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 Point 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.
Pine Tree-josephine Deposit
Pine Tree – Josephine is the most significant of the four gold mineralized deposits on the Fremont Property. The Pine Tree – Josephine Deposit has a strike length of 823 m (2,700 ft), dips moderately to steeply east-northeast, and has a maximum width of 152 m (500 ft) on surface. Historically, this Deposit has been extensively developed by numerous shafts and drifts and produced slightly more than 125,000 oz gold, primarily from shrinkage and open stope mining, until mine closure in 1942. Most of the mine development took place in a zone approximately 61 m (200 ft) wide, bounded on the hanging wall side by the Josephine Vein.
Queen Specimen Deposit
The Queen Specimen Deposit is the most northerly major alteration and mineralized zone known on the Fremont Property. The Deposit was originally developed by two separate sets of underground workings. The upper Queen Specimen workings were accessed by cross-cut adits from the hanging wall, whereas the lower Succedo workings consist of a 152 m (500 ft) internal shaft with levels developed from the River Tunnel.
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.
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 ofsurface 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.
Mineralization
Four main styles of gold mineralization are present at the Pine Tree – Josephine Deposit and generally throughout the four km mineralized trend on the Fremont Property: 1) quartz hosted free gold; 2) quartz-sulphide veins; 3) mélange stockwork and 4) oxide-gold. The quartz-hosted mineralization mainly consists of free gold in quartz. It covers 3 of the 6 veins in Pine Tree – Josephine area.
The quartz free gold domain happens as quartz only or quartz-ankerite veins without any sulphide and locally it has mariposite and/or chlorite. It happens in three of the six main veins in the Josephine – Pine Tree area, especially as internal veins of the mineralized body between the footwall and hanging wall veins.
Property Geology
The Property is located at the southern extent of the Mother Lode Gold Belt. The geology of the Property is dominated by the sedimentary Mariposa Formation (shales and greywackes with low grade metamorphism) to the west, the Melones Fault Zone in the center with serpentinite and a dioritic intrusions, and the Bullion Mountain Formation metavolcanics and Briceburg Formation metasedimentary rocks and metavolcanics to the east. The serpentinite matrix mélange in the Melones Fault Zone hosts the historical Pine Tree - Josephine Gold mine, Queen Specimen mine and Chicken Gulch and Crown Point Deposits, while the French, Evans and Ogle Lease mines where outside of the trend in tensional veins.
Within approximately 200 m of the contact between the metasedimentary rocks and the Melones Fault Zone, the rocks become highly strained. Approaching the contact from the west: slate becomes increasingly common with rare, <10 cm thick layers of strongly boudinage and sheared limestone;alteration intensity increases with proximity to the contact; and rock oxidation and chlorite alteration increase markedly within 50 m of the contact, with local stockwork areas of increased deformation, alternation, and quartz veining. This stockwork area hosts gold mineralization.
The Melones Fault Zone is a sequence of ultramafic rocks and an associated tectonic mélange that trends north-northwest and dips 45° to 60° east. Distally from the gold deposits the ultramafic rocks include fine-grained, very strongly sheared serpentinite with volumetrically insignificant asbestiform minerals observed in unaltered serpentinite outcrops as minor thin fracture fillings at the far northern end of the Property adjacent to the Merced River. These occurrences are situated far outside the hydrothermally altered mineralized zones that comprise the lode gold deposits and host rocks.