FAD Project

Geologically, the FAD deposit (FAD underground) is a continuation of the historic Ruby Hill mineral deposit  which has been down-dropped and offset by post-mineralization faults.  The exact mineralization between Ruby Hill and FAD are not the same. Ruby Hill is closer to surface and an oxide deposit, and FAD deposit is sulfide-hosted associated with carbonate replacement.  In fact, this region in Nevada is renowned for carbonate replacement deposits (“CRD’s”).

This particular region of the Eureka-Battle-Mountain trend has a history of base metal deposits which are associated with Carbonate Replacement deposits of lead-silver-zinc-gold mineralization which were discovered in the Eureka district in 1864 with substantial production primarily from 1870 to 1890.

The FAD project is located in the Ruby Hill Mining District, Eureka County, Nevada, USA, in the Prospect Mountains.  The project is located in a historically prolific mining district on the prolific Battle-Mountain-Eureka Gold Belt, approximately three miles west of the town of Eureka. Most of the Eureka District’s production was during the period of 1879 to 1890. Hecla Mining’s project report from when they owned the FAD project (1966) states that the Eureka Mining District produced 2 million tonnes of mineralized material with a value of $122 million, of which 80% was from the Ruby Hill deposit (adjusted to 2022 dollars, this value exceeds $1B).

The FAD deposit is adjacent to, and in some cases, beneath the Ruby Hill deposit, and has been separated from the Ruby Hill claims because of the differing mining methods and process methods required to process the FAD underground versus the Ruby Hill deposits (upper FAD). For clarity on deciphering between the two deposits, we sometimes refer to

The FAD Project is located directly south of the i-80 Gold Corp’s Ruby Hill project (which includes the Archimedes pit which was previously owned and operated by Placer/Barrick and more recently operated by Waterton). Unless otherwise indicated, the term “Ruby Hill”, as used throughout the Paycore website and marketing materials, refers to the historic Ruby Hill mine and its associated mineral claims which are located on our Property and are part of the FAD mineral concession, and does not refer to the project operated by i-80 Gold Corp under the same name.  Both I-80 and Paycore call their projects Ruby Hill due to the projects historically being linked together as one entity.

Geologically, the FAD deposit (FAD underground) is a continuation of the historic Ruby Hill mineral deposit (upper FAD) which has been down-dropped and offset by post-mineralization faults. However, the exact mineralization between Ruby Hill and FAD  are not the same. Ruby Hill  is an oxide deposit, and FAD is sulfide-hosted associated with carbonate replacement (also referred to as “Carbonate Replacement Deposit” or “CRD”).

This particular region of the Eureka-Battle-Mountain trend has a history of base metal deposits which are associated with Carbonate Replacement deposits of lead-silver-zinc-gold mineralization which were discovered in the Eureka district in 1864 with substantial production primarily from 1870 to 1890.  Mineralization at FAD and the Ruby Hill Mine consist of high-grade poly-metallic mineralization; gold, silver, lead and zinc. There is the presence of mineralization associated with both carbonate replacement deposits as well as Carlin-style alteration.

The replacement mineralization of Ruby Hill (upper FAD) is oxidized to the lowest mining levels, about 250 m (-800 ft) below the surface. Replacement ores on Mineral Point and on Prospect Mountain were also highly oxidized, and only small amounts of unoxidized sulfide minerals were mined at the three locations.  The Ruby Hill Fault off-sets the historic FAD underground deposit to a depth of approximately 2,400 ft.  The extent to how the historic FAD deposit or mineralization may be is still unknown due to a lack of exploration drilling.  There was very little exploration drilling completed in the 1950’s outside of where the test-mining took place at the FAD deposit which is located ~2,400 ft deep as we know it.  Most of the drilling completed at FAD was underground drilling during the 1950’s when test-mining was underway.  Paycore Minerals is the first Company to commence modern-day exploration drilling since the 1960’s and 70’s. 

Sulfide replacement deposits north of Ruby Hill, on Prospect Mountain and on Mineral Point, consist mainly of subequal amounts of pyrite, sphalerite, and galena, with subordinate amounts of hydrothermal dolomite, calcite, arsenopyrite, tennantite, pyrrhotite, quartz, and chalcopyrite

In Ruby Hill and on Prospect Mountain, much of the economic-grade material was recovered from the floors of caves where oxidation of sulfide minerals and removal of sulfur and zinc residually enriched lead, silver, and gold in the rock. The historically mined grades of 0.5 to 2 oz/ton (17 to 68 g/tonne) gold, tens of oz/ton (hundreds of g/tonne) silver, and tens of percent lead (Technical Report, March 2022) were undoubtedly derived from oxidation of sulfide deposits with grades as much as 4 times lower, as evidenced by the tenor of sulfide replacement deposits encountered by drilling north of Ruby Hill. A resource of 3.1 million tons at 3.7% lead, 8.3% zinc, 0.16 oz/ton (5.4 g/tonne) gold, and 5.6 oz/ton (190 g/tonne) silver is estimated to exist about 600 to 800 m (-2,000 to 2,600 ft) below the surface in the down-dropped block north of Ruby Hill (Technical Report, March 2022).

¹ The historic calculations presented above are neither a Resource nor a Reserve as defined by NI 43-101. Golden Hill has not done sufficient work to classify this historical estimate as a current mineral resource and have referred to this estimate as a “historical resource”; they are not treating it, or any part it, as a current mineral resource. This historical resource estimate should not be relied upon and has only been included to demonstrate the mineral potential of the FAD Property.

All significant carbonate replacement deposits in the Eureka district occur within two Cambrian carbonate rock formations, Eldorado Dolomite and Hamburg Dolomite, and the most important deposits are in Eldorado Dolomite.

A primary structural control on the distribution of replacement deposits in the Eureka district was thought to be zones of fractures in otherwise massive Eldorado and Hamburg Dolomites (Technical Report, March 2022), although fractured dolomite extends far beyond clusters of replacement deposits at Ruby Hill and on Prospect Mountain. Replacement sulfide deposits in the down-dropped blocks north of the Ruby Hill fault are commonly situated within zones of fractured dolomite.

There are multiple fractures, faulting and off-setting rock units  within the Eldorado Dolomite which is associated with the historic FAD deposit.   Both the thrust faults and normal faults were important in providing channels for mineralization -forming solutions and sites for base and precious metals deposition in this region (Technical Report, March 2022).

The host rocks in the district were deposited in the Cambrian and Ordovician ages. The carbonate replacement deposit associated with FAD is within the Cambrian carbonate rock formation, Eldorado Dolomite

The Eureka mining district occupies the southern tip of the Battle Mountain – Eureka trend of Carlin-type gold and base metal mineralization in east-central Nevada, and contains a series of gold and base metals deposits. The Eureka district is characterized by gold-silver-lead polymetallic carbonate replacement and Carlin-type gold deposits, which are the two-primary deposit-types within the district.

The stratigraphic section exposed in the Eureka district consists of a thick section of Early Cambrian to Early Cretaceous carbonate and clastic rocks that have been intruded or overlain by numerous intrusive plugs, stocks, dikes, sills, lava flows, and tuffs ranging from Cretaceous to Oligocene in age.

More than 2,100 m (>7,000 feet) of Cambrian rocks underlie the Eureka district, although, because of deformation, in no place is the complete Cambrian section intact. Cambrian rocks comprise, from oldest to youngest, Prospect Mountain Quartzite, Pioche Shale, Eldorado Dolomite, Geddes Limestone, Secret Canyon Shale, Hamburg Dolomite, Dunderberg Shale, and the Windfall Formation (Nolan and others, 1956). The Cambrian siliciclastic and carbonate rocks are overlain by Ordovician through Early Cretaceous sedimentary strata, Oligocene volcanic rocks, and Quaternary colluvium.

Middle and Late Cambrian Eldorado Dolomite and Hamburg Dolomite are the important host rocks for the carbonate replacement and Windfall gold deposits. Lesser amounts of replacement mineralization and some gold deposits occur in carbonate rocks of the Late Cambrian Windfall Formation and Early and Middle Ordovician Pogonip Group. The characterization provided below summarizes more detailed descriptions by earlier workers (Technical Report, March 2022) and emphasizes those units which are demonstrated gold mineralization hosts in the Eureka district.

Sedimentary rocks in the district provide a nearly complete record of deposition from the Cambrian through the late Mississippian (Technical Report, March 2022). The lower portion of the section, from the Cambrian Prospect Mountain Quartzite through the Devonian Devils Gate Limestone, is dominated by shelf carbonate rocks inferred to have originally been part of an eastward-thinning wedge of miogeoclinal sedimentary rocks. Carbonaceous shales and sandstones are locally interspersed among the limestones and dolostones of the lower Paleozoic section, which host the majority of the mineralization (Technical Report, March 2022).  See Figure XX below of stratigraphic column in the Eureka district.

Eldorado Dolomite, the host rock for the replacement deposits in and north of Ruby Hill, is composed of ~760 m of massive, coarsely crystalline bluish-gray dolomite and limestone, including two varieties of dolomite and minor remnants of fine-grained and well-bedded limestone. One variety of dolomite is blue-gray, massive, and thick bedded. The second variety is lighter gray, coarser grained, displays little texture, and predominantly encloses the replacement deposits. Both varieties of dolomite are finely fractured, and both are interpreted to have been recrystallized, in part hydrothermally, from the fine-grained and well-bedded limestone (Technical Report, March 2022).

The Eldorado Dolomite is succeeded by the Geddes Limestone, Secret Canyon Shale, and Hamburg Dolomite. The Hamburg Dolomite is similar in appearance to Eldorado Dolomite and is also finely fractured in the vicinity of replacement deposits. Some Hamburg Dolomite is also thought to be a product of hydrothermal alteration (Nolan and others, 1956). Hamburg Dolomite is marbleized and altered to pyroxene-garnet skarn and hydrous skarn south of Ruby Hill and on Mineral Hill and contains replacement deposits in the vicinity of Prospect Mountain and on Mineral Point (Technical Report, March 2022).  

The Hamburg Dolomite, host to both carbonate replacement mineralization and to the Carlin-type mineralization at the near-by Windfall, Rustler, and Paroni mines, consists of 300 m of dark gray, massive limestone with dolomite horizons. Although the Hamburg Dolomite occurs roughly 300 m strati-graphically above the Eldorado Dolomite, they are lithologically similar (Technical Report, March 2022).

Stratigraphic column of Cambrian–Ordovician rocks in the Eureka district, with unit descriptions, thicknesses, and the locality of the measured sections

Geological maps, sections, and holes as presented in the 2021 technical report, show that Cambrian-Ordovician sedimentary rocks, Cretaceous granodiorite and Quartz porphyry, and Tertiary Volcanic rocks around the property are overlain by Quaternary alluvium. More than 1,000 m of litho-stratigraphic units were defined and mapped within the property. Sedimentary rocks are the most abundant in the study area. In the north part of Ruby Hill and around the property, a part of the stratigraphic column includes the lower Paleozoic formations exposed on the surface. Sedimentary rocks within the property in drill holes and in underground opening of the Ruby Hill area and the property include, from oldest to youngest, Prospect Mountain Quartzite, Eldorado Dolomite, Geddes Limestone, Secret Canyon Shale, Hamburg Dolomite, Windfall Formation, and Pogonip Group.

Sulfide replacement deposit on FAD property consists mainly of subequal amounts of pyrite, sphalerite, and galena, with subordinate amounts of hydrothermal dolomite, calcite, arsenopyrite, tennantite, pyrrhotite, quartz, and chalcopyrite. Locally, pyrite, galena, and sphalerite exist within sulfide replacement masses north of Ruby Hill and in Prospect Mountain. Grain size of pyrite, sphalerite, and galena and hydrothermal dolomite are present in Ruby Hill deposits; sulfide aggregates in quartz porphyry tend to be slightly coarser grained. Gold occurs mostly in pyrite, based on metallurgical tests.

Jackson fault, Adams Fault, and Ruby fault are main structures around the FAD property. Workers in the northern Eureka district have entertained hypotheses that many faults possibly were conduits for fluids that produced base-metal mineralization, yet it is now established that many of the faults clearly offset the Ruby Hill stock and base-metal mineralization, as is also supported by data from ground magnetics and drilling (Technical Report, March 2022)

The northwest-striking, down-to-the-northeast Ruby Hill normal fault, along with the Martin and perhaps the Office faults, is one of the earliest normal faults to cut and offset the Ruby Hill stock and mid-Cretaceous carbonate-hosted base metal mineralization. The Jackson branch cuts and offsets the Ruby Hill fault.

Existing data shows that the FAD deposit is a mid-Cretaceous disseminated carbonate-hosted base metal type deposit. The Eldorado dolomite (middle Cambrian) is the primary host rock. Ruby Hill stock, which was emplaced in the late Early Cretaceous, was a source of hydrothermal fluids, a source of sulfide deposits. However, none of the faults around the FAD deposit show that they acted as conduits for hydrothermal fluids. In contrast, Eldorado dolomite and the FAD deposit were both cut and offset by surrounding faults.

Recent drilling demonstrates that a carlin-type deposit also exists on the FAD site (in addition to the sulfide deposit discussed above).  Additional work is being completed  to determine if a carlin-type deposit or any overprinting mineralization has occurred within the FAD property.

Distribution of alteration in the Project area falls into four broad categories: silicification, marble and hornfels, bleaching, and sanding (Technical Report, March 2022)

Figure: Local geological Cross Section through the Locan and FAD Shafts which are both located on the FAD Project. The Ruby Hill Fault is the main fault which is believed to have down-dropped the FAD Deposit which is at a depth of approximately 2,400ft or ~750 metres.

There are many historic mining operations within the XXkm strike of the FAD Project.   The image below identifies the Carlin-Type deposits with a yellow dot and the carbonate replacement deposits (CRDs) in red.  The Image below is a geological map of the Eureka district showing various deposits along the faults zones within the major mining belt.  The solid blue line identifies fault systems which have been mapped and widely knonwn in the district.  The dashed blue line depicts the poorly mapped structures which have not been as widely known.  These faults structures are very important as they are typically associated with fluids and mineralization within the district. The FAD Deposit is located on the dashed-line which is known as the Jackson Fault.  The Jackson Fault is of particular interest given that this fault structure has been poorly mapped and widely unknown historically, becoming a target of interest for the potential to host mineralization.

Multiple splay faults converge into the Jackson Fault zone including the Ruby Hill fault which appears to have been down-dropped approximately 400m.  The cross-section below identifies the Ruby Hill Fault which demonstrates this displacement of the host rock, the Eldorado Dolomite in purple, which has been faulted and off-set approximately 400m in depth.    The historic FAD Deposit which has a non 43-101 mineral resource is located at approximately 700m (FAD underground).  The FAD Shaft seen in this diagram reaches an approximate depth of 750m.  Intermittent mining took place from 1956-58 when it was shut down due to water intake and the lack of technology to pump water from the mine.

here is potential to define a near-surface oxide gold deposit near the historic mine workings at Ruby Hill (Upper FAD). There is historic high-grade production of 1.3 million ounces gold at 0.89 ounces per ton and 38 million ounces of silver at 21.1 ounces per ton.¹

Deeper poly-metallic mineralization at FAD underground has the potential to become one of Nevada’s premier “new” deposits with no work having been completed on the project in +50 years.  There is a historic non 43-101 resource estimate on FAD of 3,903,000 Tons grading 5.14 g/t Au, 196.46 g/t Ag, 7.99% Zn & 3.80% Pb¹,².   The  FAD has limited exploration drilling with few holes drilled outside the FAD historic resource area¹. A large majority of the drilling at FAD was done from underground after the FAD Shaft was sunk.  The outliner exploration holes that were drilled intercepted the Eldorado Dolomite in multiple locations.  The Eldorado Dolomite is the favourable rock unit which is associated with gold, silver, lead and zinc mineralization in this region.

¹The historical estimates contained in this presentation have not been verified as current mineral resources. A “qualified person” (as defined in NI 43-101) has not done sufficient work to classify the historical estimate as current mineral resources or mineral reserves, and the Company is not treating the historical estimate as current mineral resources or mineral reserves. Historic production from the  of 1.6 Moz of gold @ ~0.89 oz/ton, 38 Moz of silver @ 21.1 oz/ton (from 1.8 Mtons).

²  Source: 1974 Feasibility Study – Hecla Mining Company

 The FAD deposit lies within the Ruby Hill mining district. Many adjacent properties and historic mining operations exist.  Directly next to FAD is the i-80 Gold Corp project called the Ruby Hill Mine or Archimedes Pit (even though the Ruby Hill concessions are contained within the FAD project). This section discusses the history of the i-80 Gold Corp project, and its historic antecedents.

After Hecla’s departure from the project (Technical Report, March 2022, Section 6.5.2), the entire Ruby Hill mining district sat dormant for a number of years. The US Smelting and Refining Company reworked some of the dumps at the existing tailings leach pads in the 1980s.

In 1992, Homestake Mining Company purchased the property. For the duration of the Homestake/ Barrick period, the FAD deposit was included in the general land and claims package of the Ruby Hill Mine but was not developed or explored.

Shortly after purchasing the project, Homestake conducted a drilling program and found significant mineralization in what would later become the Archimedes pit (Wood 2021). In 1997, Homestake sought and received a permit to establish an open-pit mine and processing plant. Plans called for the mine to be in production by 1998, employing more than 100 workers. The mine life was initially estimated at seven and one-half years.

Archimedes (located ~1km from FAD) is a Carlin-style sediment-hosted gold deposit in carbonate rocks. The ore is a mixture of jasperoid and decalcified limestone exhibiting strong structural controls. Micron-size gold is associated with oxidized pyrite sites and is strongly fracture controlled. Deeper portions of the east Archimedes resource are sulfidic, and root-zones include retrograde-altered base metal skarn and marble hosts. The mineralized area closely adjoins a Cretaceous porphyry intrusive and may be genetically linked to it, as both base metal-related adularia and the intrusive yield similar radiometric ages. Some evidence suggests the presence of a younger cross-cutting Au-As-Hg system superimposed on the earlier base-metal system and associated with Oligocene magmatism. The West Archimedes deposit is about 780 m long, plunging gently S60 degrees E and covered by 15 to 150 m of partially cemented calcareous alluvium. The deposit is subtabular to ovate in cross section, branching locally at structural intersections. The orebody has a central elongated lens of higher grade jasperoid ore enclosed by a more tabular envelope of lower grade decalcified limestone ore.

The mines centered on the Archimedes pit produced 28,284 ounces of gold in the first quarter of 2000 and reported the lowest cost per ounce of all the mines in operation by Homestake. The mine also received the best safety-performance awards in the company. Barrick Gold Corporation acquired the Homestake Mining Company in 2001. Barrick continued to mine and also began concurrent reclamation work. Barrick Gold stopped mining in 2002, because low gold prices and other factors forced a slowdown in mining throughout Nevada.

As the gold market improved, Barrick resumed mining in in 2006 The first gold was poured in 2007 and the mine poured its one-millionth ounce of gold in July 2009. A pit slope failure in 2013 and declining gold prices put the project on standby (McKown, 2014). At the time of shutdown, the project had produced 1.4 million ounces of gold (Waterton, 2015).

Barrick commissioned a technical report for the Ruby Hill Mine property on March 16, 2012. Even though the claim package included the FAD deposit, the 2012 technical report did not estimate resources from FAD. It is mentioned as a potential exploration project within the larger concession (RPA. 2012)

Historical metallurgical test-work was performed by Hecla Mining (1966) and other predecessors of the FAD Project and is now over sixty years old with no additional  modern-day testing.  The results from the preliminary metallurgical test program, completed on the 1966 study for the FAD project, resulted in recoveries of;

Metallurgical testwork competed in the 1974 Feasibility by Hecl6666a Mining,  indicated a baseline recovery of 89% gold, 75% silver, 85% zinc an 76% lead.  With metallurgical work completed in the mid-70’s, there may be opportunity to improve recoveries with newer technologies. 

The FAD project has not been drilled in over 50 years since.  Paycore Minerals Inc is the first company to complete modern-day exploration and drilling.

The existence of the FAD deposit (FAD underground) was hypothesized in the 19^th century when miners noticed the abrupt termination of the Ruby Hill deposit at the Ruby Hill Fault. Due to the fact that Ruby Hill was so productive — indeed, mines in the region dominated the late-19^th century lead metals market, the idea that the deposit continued was attractive to large-scale mining companies (led by Hecla Mining). As a result, in the mid-20^th century, they began a large-scale exploration effort which cost $3M in 1950 (about $20M today). This effort discovered the FAD deposit, an underground high-grade sulfide polymetallic mineral body containing lead, zinc, copper, silver, and gold. As hypothesized, Hecla Mining confirmed that a series of post-mineralization normal faults has down-dropped a portion of the original Ruby Hill mineralization deposit down to ~2,500 feet below ground surface, with a second normal fault further offsetting the deposit a total of 3,000 feet below ground surface. Due to challenges with groundwater and drilling, and due to the high cost of the project, the exploration efforts were terminated, and the mine was never put into full production after the initial test-mining which took place between 1956-58.