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 consists of three Arizona Mineral Exploration Permits, 77 BLM mining claims and two patented mining claims covering approximately 1,389 ha. Copper Fox is required to make annual option payments of $US40,000 (two remaining) to own a 100% interest in the patented mining claims.
The work to date has identified two exploration targets that strongly supports the presence fo a large porphyry copper system, however, it is not known if the exploration targets identified are part of the same porphyry system. The Company continues to systematically advance the project through the exploration stage with the overall objective of identifying and optimizing drill targets to define the porphyry system at depth.
To advance the project Copper Fox intends to focus on Target #2 due to its significantly larger size, proximity to surface and location within the property. The work required to continue target definition includes additional rock characterization sampling to map the full extent of the phyllic alteration, along with an airborne magnetometer and deep penetrating geophysical survey to better define the geometry of the chargeability/resistivity body. Successful completion of this exploration work will allow the Company to select drill targets.
This target has a surface expression of 2,000m by 1,200m and is located at the north end of the property. Within the Copper Creek Granodiorite that underlies this portion of the property, a 600m by 600m area contains 28 mineralized breccia pipes which were the focus of the historical mining activities (i.e. Magma Chief Mine) on the property. Copper values in outcrop range from 0.076% to greater than 0.25% and from 0.007% to 0.025% for molybdenum. A chargeability/resistivity body measuring 500m long by 500m deep occurs at a depth of approximately 400m below the mineralized breccia pipes exposed on surface. Between 2006 – 2008, Bell Copper drill tested seven of these breccia pipes and intersected intervals of medium to high grade copper mineralization to a depth of 506m. The drilling and geophysical results show that the “roots” of the Magna and Campstool breccia pipes correlate with the chargeability/resistivity body.
Geochemical mapping (K/Al: Na/Al ratios) outlined a NNW trending area approximately 900m long by 500m wide of phyllic alteration surrounded by potassic alteration. The phyllic alteration is interpreted to be the southern extension of the large area of phyllic alteration shown on the regional geology map for this area.
This target is underlain by the Copper Creek Granodiorite, Glory Hole Volcanics and Pinal Schist. The eastern portion of this target has been intruded by a significant number of NNW and ENE trending grey porphyry, dark porphyry, granite porphyry and diorite porphyry dikes. Forty-seven mineralized and non-mineralized breccia pipes have been located within this target.
A 2,800m long by a minimum of 400m wide area within the Copper Creek Granodiorite and Glory Hole Volcanics exhibits the chargeability/resistivity signature of a porphyry copper system. This anomaly is truncated to the west by a west dipping range-front fault and plunges to the northeast under the Glory Hole Volcanics. The chargeability/resistivity body extends from surface to a depth of greater than 800m.
Phelps Dodge drilled five drill holes within Target #2 (including a portion of the chargeability/resistivity body) in the early 1970’s. The collars of these holes were located, and analyses of the drill cuttings by Copper Fox yielded up to 0.23% copper. The core descriptions, hole depths and analytical results from these historical holes are not available.
Mineralized outcrops within this target returned a maximum copper value of 1.0% (Median Value 113 ppm/Average Value 256ppm) and a maximum molybdenum value of 0.071% (Median Value 2.2 ppm/Average Value 12.3 ppm). Copper-molybdenum mineralization occurs in NNW and ENE trending, steep and shallow dipping veins and veinlets hosted in Copper Creek Granodiorite and Glory Hole Volcanics. The higher copper-molybdenum concentrations occur in grey porphyry dikes.
Geochemical mapping using (K/Al: Na/Al) ratios outlined a NNW trending area approximately 3,000m long by 1,000m wide of phyllic alteration that covers the southern portion of the chargeability/resistivity body, the mineralized outcrops and breccia pipes in this area.
Arizona Porphyry Copper Deposits:
The Sombrero Butte project is located in the porphyry copper metallogenic province of the southwestern United States; one of the largest copper districts in the world. This district hosts numerous large porphyry copper mines including the world class Resolution porphyry copper deposit. Arizona is a mining friendly, politically secure jurisdiction with readily accessible infrastructure.
The property is located at the intersection of an ENE-trending belt of porphyry copper deposits which include; Lakeshore, Silverbell, San Manuel/Kalamazoo, Safford and Morenci, and a NNW-trending belt that includes; Ray, Superior (Resolution), Christmas and Miami-Inspiration. The project is located 2 miles south of the Copper Creek porphyry copper deposit and 5 miles east of the former San Manuel/Kalamazoo copper mine.
Early Mining History:
Historical copper production from the Sombrero Butte project is reported to have occurred between 1903 and 1920 at the north end of the property. These mines exploited the mineralized breccia pipes on the Audacious claim. An article in the Arizona Mining Journal (1919) reports low-grade” ore assaying 3-5% copper, with higher grade ore from along open cuts and tunnels assaying 20-33% copper, and low-grade dump material assaying 6-8% copper at the Magma Chief mine.
Most porphyry copper deposits in the southwestern United States (including Copper Creek) were emplaced during the period of Laramide tectonism (Late Cretaceous - Early Tertiary; 80-50 Ma). This tectonic event was accompanied by a major ENE-WSW compressional regime resulting in northwest-trending, basement sourced, uplifted blocks and a widespread ENE-trending brittle structural fabric.
The Sombrero Butte Property is situated on an uplifted block and lies at the intersection of ENE and NNW trending belts of porphyry copper deposits.
The property is centered over a multi-phase Laramide age intrusive complex. The Copper Creek Granodiorite; the most widespread Laramide intrusion in the Sombrero Butte area has been dated (K-Ar and 40Ar/39Ar methods) between 60 and 68 Ma (Anderson et al., 2003).
The oldest rocks on the property are the Precambrian Pinal Schist located in the south-central portion of the property. The eastern side of the property is covered by Cretaceous age (early Laramide age) Glory Hole Volcanics. The Copper Creek Granodiorite is the most widespread Laramide intrusion located mainly in the central and western side of the property. Intruding the Copper Creek Granodiorite in the center of the property is a (600m by 400m) Laramide age “dark porphyry” intrusive plug. The Tertiary Galiuro Volcanics occupy the west side of the property and form the range-front knob referred to as Sombrero Butte. Small plugs of Laramide age granodiorite and dykes of variable composition intrude the Glory Hole Volcanics and the Pinal Schist indicating the presence of the Copper Creek stock at depth.
Two swarms of mineralized breccia pipes occur on the property. The first swarm occurs at the north end of the property and was the source of the historical mining activities. The second swarm occur in the south-central portion of the property and shows a strong correlation with the copper mineralization, chargeability/resistivity body and phyllic alteration in Target #2.
The property lies along a northwest to southeast trend of Laramide age porphyry copper centers in Arizona. A regional scale, range-front fault (estimated offset +/- 800m) marks the western boundary of the Copper Creek Granodiorite on the property. A second range-front fault is located approximately 1km to the east of this fault and marks the western extent of the chargeability/resistivity body.
Two interpreted ENE trending faults cross the property. The first fault follows the trace of Scanlon Wash (north side down) across the northern portion of the property and possibly explains the significant increase in depth to the top of the chargeability/resistivity body in Target #1 as opposed to the near surface chargeability/resistivity body in Target #2 south of this fault. Clark Wash represents the surface trace of an ENE fault that crosses the southern portion of the property and marks the southern end of the chargeability/resistivity body.
The North Fork of Clark Wash is a NNE trending, linear topographic feature along which numerous breccia pipes are located. This linear feature is interpreted to be either a fault zone or zone of weakness.
The copper mineralization in the breccia pipes at the northern end of the property yielded ages from 57 to 60 Ma. The mineralization occurs predominately in the matrix of the breccia pipes and consists of chalcopyrite, bornite and pyrite. High-grade mineralization in the breccias typically occurs as masses and clots of copper minerals filling open spaces or as sheeted veins along the edges of the pipes. Copper, molybdenum, gold, and silver concentrations vary considerably from breccia to breccia (see Exploration Results below).
On surface, the mineralization in the Copper Creek Granodiorite, and Glory Hole Volcanics occurs in strongly fractured outcrop along directions of N50-85E and N-S to N25W, consistent with other Laramide copper porphyries in Arizona. In Target #2, abundant limonite (after pyrite) veining occur in outcrop.
In the late 1990’s, AMT International (AMT) collected 125 surface rock chip samples yielding up to 3% Cu and 270 ppb (0.27g/t) Au. A Gamma ray spectrometry survey (861 stations) outlined two regions of elevated rare earth elements. High concentrations of rare earth elements are common to high-grade copper-molybdenum breccia pipes in the Bunker Hill Mining District located immediately north of the property.
Between 2006 and 2008, Bell Copper drilled 34 diamond drill holes into seven breccia pipes in the vicinity of the former Magma Chief Mine in the northern portion of the property. Selected mineralized intervals from the Bell Copper drilling are listed below.
|Pipe||DDH||From (m)||To (m)||Int. (m)||Cu (%)||Mo (%)||Au (ppm)||Ag (ppm)|
The mineralized intervals listed in the above table do not represent true widths.
The geochemistry, mineralization and associated gangue mineral suggests that the breccia pipes originated from three separate/distinct sources. A brief description of the breccia pipes is:
- The Magna-Campstool-Victors pipes contain significant copper mineralization
- The Audacious-Rattler pipes contain significant copper mineralization accompanied by high concentrations of Arsenic, Stibnite, Tungsten and Manganese
- The Saguero breccia pipe is not mineralized with tourmaline in the matrix and as thin veinlets.
In 2015, Copper Fox completed two NW-SE oriented, 6km long lines of reconnaissance level, Titan-24, DCIP geophysical survey. The line separation is 400m.
The survey located two distinct chargeability/resistivity targets. Target #1 is located at the north end of the property and occurs below a swarm of mineralized breccia pipes. Target #2 is in the central portion of the property.
Target #1 occurs at a depth of approximately 400m below the historical mining activities. The northern end of Line-1 (located 400m to the west) is underlain by Copper Creek Granodiorite which exhibits background chargeability. In the northern portion of Line-2, a 500m long by 500m deep chargeability/resistivity body was located at a depth of approximately 400m below surface hosted in Copper Creek Granodiorite. The historical diamond drilling and geophysical survey successfully mapped the down dip extension of the sulphide mineralization in the breccia pipes to this chargeability/resistivity body. This chargeability/resistivity body crosses the property boundary to the north.
Target #2 is in the central portion of the property is underlain by Copper Creek granodiorite, Glory Hole Volcanics and Pinal Schist. The southern end (stn 0m to stn 1025m) of Line-1 is underlain by Glory Hole Volcanics and Pinal Schist that exhibits erratic chargeability from surface to a depth of 400m. At stn 1025, the chargeability response increases abruptly where the range-front fault intersects the survey line. From survey stn 1025m to stn 3000m, the survey line is underlain by Glory Hole Volcanics and Copper Creek Granodiorite that exhibits low chargeability from surface to a depth of 400m at which depth the chargeability response increases significantly (+ 20mrad) and continues to a depth of greater than 800m. The remainder (stn 3000m to stn 6000m) of Line-1 is underlain by Copper Creek granodiorite with a very low to background chargeability response.
Line-2 located 400m east of Line-1 exhibits a significantly larger and stronger chargeability response. The survey line from stn 0m to stn 800m is underlain by Copper Creek Granodiorite exhibiting background chargeability. From stn 800m to stn 1500m is underlain by Glory Hole Volcanics and from stn 1,500 to stn 4,500; the survey line is underlain by Copper Creek Granodiorite. From stn 800m to stn 2,800m a strong (+30mrd) chargeability signature extends to a depth of 400m and then transitions at depth into a 1,500m long zone (stn 1,500m to stn 3000m) of high resistivity/low chargeability (< 10mrad) that extends from 400m to approximately 800m below surface. The 1,500m long zone of high resistivity and low (<10 mrad) chargeability is interpreted to represent the potassic altered core of the porphyry system. At a depth of 400m, surrounding the interpreted potassic core, to the south is a 600m wide zone and to the north a 200m wide zone of moderate chargeability (10-30mrd) (“phyllic alteration zone”). The zones of moderate chargeability transitions outward to a 300-400m wide zone of high chargeability (>30mrad) interpreted to represent the “pyritic shell” commonly observed in porphyry copper systems. The surface mapping, alteration geochemistry and the mineralized breccia pipes support the geophysical interpretation.
A comparison of the trace element geochemical data with “pathfinder” elemental (Mo, W, Se, Te, As, and Sb) ranges for porphyry copper systems suggests the current topographic surface in Target #2 is either at or near the transition from the deep sericite (phyllic) zone (above the copper shell) to the potassic alteration zone.
Alteration Indicator Minerals:
To date, approximately 60 mineralized and non-mineralized breccia pipes have been located within Target #2. Twelve breccia pipes located within this target contain the clay mineral dickite, a hydrothermal alteration mineral (high temperature-acidic conditions) that occurs in multiple porphyry copper deposits throughout Arizona including the San Manuel-Kalamazoo deposit located 5 miles west of the property.
The zone of phyllic alteration in Target #2 covers the southern portion of the chargeability/resistivity body. Additional rock characterization sampling over the northern portion of Target #2 is required to establish the full extent of the phyllic alteration to the northwest. The Pathfinder Element data, K/Al:Na/Al mapping and geophysical interpretation show a strong correlation and support the presence of the phyllic alteration zone of a porphyry copper system.