Sombrero Butte is a Laramide age, exploration stage, porphyry copper project located in the Bunker Hill Mining District, 44 miles northeast of Tucson, Arizona. The project is contiguous to the north with Faraday Copper’s Copper Creek porphyry copper project. Historical copper production occurred between 1903 and 1920 from breccia pipes on the Audacious claim at the north end of the property with reports of ‘low-grade ore assaying 3-5% copper and higher-grade ore from along open cuts and tunnels assaying 20-33% copper’.
The porphyry copper deposits in Arizona are located in the “southwestern North America porphyry copper province”. This copper province is estimated to have a total copper endowment of approximately 295 Mt of copper, 96% of which is hosted in porphyry deposits of Laramide age (45-80 Ma). Arizona is a Tier 1 mining friendly, politically secure jurisdiction with excellent and readily accessible infrastructure.
In 2012 Copper Fox purchased a 100% working interest in the Sombrero Butte project. The project consists of three Arizona Mineral Exploration Permits, 77 BLM mining claims and two patented mining claims covering approximately 1,389 ha. In October 2021 Copper Fox made their final option payment to own a 100% interest in certain unpatented and patented mining claims.
A project wide, full spectrum Hyperspectral survey collecting continuous Visual and Near-Infrared (‘VNIR’) and Short Wave Infrared (‘SWIR’) data was completed in an attempt to map the extent of the advanced argillic alteration associated with the large chargeability target located in the centre of the project. In addition, combining the Hyperspectral survey data with the previously collected trace element geochemistry could generate mineral exploration indicators to better identify areas of alteration indicative of porphyry copper mineralization not readily visible on surface.
The exploration model used to advance the exploration of the Sombrero Butte project is similar to that being used to advance the Copper Creek porphyry copper deposit located 3km to the north. Faraday Copper recently announced an updated mineral resource estimate for the Copper Creek porphyry copper deposit outlined below:
Mineral Resource Estimate for Faraday Copper’s Copper Creek porphyry copper project (see Faraday Copper news release dated July 6, 2022)
- Measured mineral resource of 65.1 million tonnes (Mt) at a grade of 0.61% Cu, 0.011% Mo and 1.7 grams per tonne (g/t) Ag, containing 872.9 million pounds (Mlb) of Cu, 15.7 Mlb of Mo and 3.5 million ounces (Moz) of Ag.
- Indicated mineral resource of 290.0 Mt at a grade of 0.47% Cu, 0.007% Mo and 1.2 g/t Ag containing 3,034.2 Mlb of Cu, 47.2 Mlb of Mo and 11.0 Moz of Ag.
- Inferred mineral resource of 75.0 Mt at a grade of 0.38% Cu, 0.007% Mo and 0.8 g/t Ag containing 634.9 Mlb of Cu, 12.0 Mlb of Mo and 2.0 Moz of Ag.
The Copper Creek deposit is hosted in Copper Creek granodiorite which extends south onto the Sombrero Butte project. The geology of the Sombrero Butte project consists primarily of Glory Hole volcanics and the Copper Creek granodiorite stock, both of Laramide age, intruded by late-stage andesitic and porphyry dikes of variable composition.
The Sombrero Butte project hosts multiple mineralized and non-mineralized magmatic breccia pipes that are similar to the Copper Creek porphyry copper deposit. In the central portion of the project breccia pipes containing the mineral dickite, an indicator of advanced argillic alteration, associate with a large positive chargeability signature. The mineral dickite has been found in major porphyry copper systems including Resolution, Bisbee and San Manuel, well known copper deposits located in the Laramide porphyry copper belt in Arizona.
The Copper Creek granodiorite has been dated by K-Ar and 40Ar/39Ar methods, yielding ages between ~60 and 68 Ma. Mineralization in the breccia pipes hosted in the Copper Creek granodiorite has been dated by K-Ar, Re-Os, and 40Ar/39Ar methods, yielding ages between ~57 and 60 Ma.
The porphyry copper footprint consists of two distinct targets located in the footwall of a NNW trending regional scale “Range Front” fault system.
Target #1 is located at the north end of the property and measures approximately 2,000 m by 1,200 m. This area is underlain by the Copper Creek Granodiorite and Glory Hole volcanics. Within this target a 600 m by 600 m area hosts 28 mineralized and non-mineralized magmatic breccia pipes which were the focus of the historical mining activities (i.e., Magma Chief Mine). These breccias are characterized by intervals of high-grade copper mineralization and in some of these breccias, the copper is accompanied by low but significant concentrations of molybdenum-gold-silver.
Historical drill holes DDH SB-03 and DDH SB-23 intersected several mineralized breccia pipes and tested a significant interval of the Copper Creek granodiorite away from the breccia pipes. Both holes were drilled from the same location.
DDH SB-03 was drilled to the northeast towards a chargeability body and intersected strong to moderate chalcopyrite +/- bornite in veins and veinlets in the Copper Creek granodiorite commonly associated with pervasive K-feldspar flooding in the interval from 492 to 578 m. This interval returned a weighted average of 1,414 ppm (0.14%) copper and 30 ppm molybdenum over the 86 m core interval with individual sample intervals up to 0.64% copper and 0.019% molybdenum.
DDH SB-23 was drilled to the southeast. The interval from 524 to 1230.7 m (end of the hole) the Copper Creek granodiorite contains intervals of quartz + K-feldspar + chalcopyrite +/- bornite stockwork veinlets with pyrite becoming the dominant sulphide mineral from 1035 to 1230.7 m. The interval from 524 m to the end of the drill hole has not been sampled and analyzed.
Rock sampling outlined overlapping areas of copper mineralization (>500 ppm) measuring 1000 by 750 m and molybdenum mineralization (>30 ppm) measuring 750 by 600 m located above and west of the deep-seated chargeability/resistivity body located on L-2 of the 2015 geophysical survey. The top of the chargeability body occurs at depth of approximately 400 m, located below the Victor’s breccia pipe swarm. These pipes were tested by a series of shallow drill holes that intersected variable core intervals of high-grade copper mineralization.
Target #2 is located in the center of the property and is underlain by the Copper Creek Granodiorite, Glory Hole Volcanics and at least 60 leached, intensely altered mineralized and non-mineralized breccia pipes. Twelve of these breccia pipes contain the mineral dickite, indicating the advanced argillic alteration stage of a porphyry system.
An open-ended northeast plunging chargeability body measuring approximately 2,200 m long by at least 600 m wide has been mapped to a depth of 800 m. Modelling of the chargeability signature indicates a low chargeability core (located approximately 400 m below surface) draped by a significantly higher chargeability signature extending to surface and horizontally over a distance of 2,000 m.
Rock sampling outlined overlapping areas of copper mineralization (>500ppm) that measures 2,300 m by 700 m and molybdenum mineralization (>20ppm) that measures 1,500 m by 500 m. The copper-molybdenum mineralization is located within the chargeability/resistivity signature.
Historical diamond drilling (2006-2008) of seven of the magmatic-hydrothermal breccias in Target #1, intersected variable thicknesses of copper mineralization occurring as masses, clots and sheeted veins. The mineralogy and associated alteration in these breccia pipes strongly suggest multiple episodes of copper mineralization which in some cases contained significant concentrations of +/- molybdenum-gold-silver (see table of selected mineralized intervals below). Surface mapping of mineralized veins/fractures outside the breccia pipes occurs along N50-85E and N-S to N25W trends consistent with other Laramide copper porphyry systems in Arizona.
In 2022, Copper Fox completed a combined high sensitivity, airborne magnetic and radiometric survey to better define the location and depth of late stage felsic intrusives related to a buried porphyry system. A magnetic vector inversion study using the airborne magnetic data has identified several cylindrical shaped pipe-like positive magnetic anomalies interpreted to be late-stage felsic intrusives with associated potassic alteration due to the presence of hydrothermal magnetite. The 2022 survey also identified several NNW trending previously unrecognized interpreted regional scale fault systems.
Historical Drilling Results
Between 2006 and 2008, Bell Copper drilled 34 diamond drill holes into seven breccia pipes in the vicinity of the former Magma Chief Mine at the north end of the property (Target #1). Selected mineralized intervals from the Bell Copper drilling program are listed below.
Notes: m=meters, %= percent, tr=concentration of less than 0.001% Mo, 0.005 Au g/t and 0.10 g/t Ag, Cu=copper, Mo=molybdenum. Au=gold, Ag=silver. The mineralized intervals listed in the above table do not represent true widths