Tombstone Joint Venture Highlights
- Aztec holds a 75% interest in the Tombstone Property Joint Venture, which includes most of the original patented mining claims in the district as well as some recently acquired properties.
- Recent Aztec Drilling: The main target of the 2020 Phase 1 RC drill program was to test for shallow, bulk tonnage, heap leachable, epithermal gold-silver oxide mineralization adjacent and below the previously mined Contention pit. Future drilling is expected to focus on extensions of the shallow oxide mineralization already tested, as well as larger, deeper “Taylor-type” CRD targets along and adjacent to the Contention structures.
- Tombstone produced 32M ounces of Silver, 240K ounces of Gold, 65M pounds of Lead, and 1.1M pounds of Zinc from 1.5M tons and mostly from oxide ores between 1878 and 1939
- Aztec controls 1,0734.1 acres (434.4 hectares), which includes most of the original patented claims in the heart of Tombstone Mining District and Contention Pit
- Historic mining conducted on thin, but high-grade and oxidized mantos (CRD’s) within the Bisbee Group sedimentary package and on high-grade veins
- Over to 2,000 meters (6,600 ft) of prospective Paleozoic limestones potentially to be found below the Bisbee Group sediments
- Nearly all historic mining terminated at base of Bisbee due to water table, deeper mining limited due to lack of technology, mine flooding
- Rock chip sampling highs: 23.5gpt Gold, 3,178gpt Silver, 14.21% Lead, 5.52% Zinc, and 1.38% Copper
Aztec has recently completed a reverse circulation (RC) drill program conducted at the Tombstone project in Southeastern Arizona from August to November 2020 and is currently completing a 2021 Phase 1 RC program (as of July 2021) . The 2021 20-hole, 2,900 m Phase 2 program is designed to step along strike and down dip from the Phase 1 drill intercepts in 2020 to expand the shallow, broad, bulk tonnage gold-silver mineralization discovered around and below the Contention pit.
The 2020 Phase 1, 21-hole, 2,993 meter drill program tested for the potential for shallow, broad, bulk tonnage gold-silver mineralization around and below the Contention open pit and underground mine workings, and was successful in finding it. The Contention Mine was historically the largest and highest grade silver mine in the Tombstone silver district (32 million oz past production) in the late 1800’s-early 1900’s. More recent Contention open pit mining in the early to mid-1980’s focused on gold-silver mineralization to approximately 60m depth entirely hosted within the Cretaceous Bisbee group sandstones. Most other mines in the district were much smaller veins and mantos hosted within the lower Bisbee and partially within the underlying Paleozoic limestones.
The following table is a summary tabulation of all 2020 drill hole results.
- AuEq is calculated using an 80:1 silver:gold ratio
- Au, Ag, and AuEQ are in grams per ton, “gpt”
- Additional information related to true thicknesses on individual holes can be found in prior NR’s dated Sept 29, Oct 21, Nov 30, and Dec 22
Previous work by Aztec includes a surface exploration program of structural and geological mapping, rock sampling, trench sampling, and airborne geophysical surveying on the Tombstone Project in southern Arizona. (map link here).
The focus of this exploration program was to better define the three styles of mineralization known to exist on the properties and to identify top priority targets for drilling. The three types of mineralization at Tombstone are as follows:
- Potential high grade, bulk tonnage carbonate replacement deposits (“CRD”), which could lie below the Bisbee Group in the underlying Paleozoic limestones, a geologic setting similar to the Taylor deposit of Arizona Mining, located only 65 kilometers southwest of Tombstone, who recently received a CAD$1.8 billion friendly take-over bid by South 32
- Bulk tonnage gold-silver epithermal disseminated and stock-work mineralization also cutting the Bisbee Group and focused around rhyolitic quartz-feldspar porphyry dikes, on which the Contention open pit, heap leach mine was developed in the 1980’s (map link here)
- High grade silver-gold-lead (zinc-copper) veins cutting Cretaceous Bisbee Group clastic sediments, which hosted most of the historic mines in the Tombstone district
Tombstone’s Potential Upside
The district is underlain by the same Paleozoic limestone sequence that hosts the massive Taylor zinc-silver-lead deposit of Arizona Mining Inc. located only 65 kilometers west of Tombstone. Arizona Mining is currently the subject of a friendly $1.8-billion takeover bid by South32.
Aztec’s focus is discovering new zones of epithermal and CRD mineralization because they typically form much larger and high-grade mineralized bodies. However, the small historic high-grade silver mines are very useful in showing where mineral-controlling structures are located. The geological, geochemical and geophysical surveys have identified several prospective areas with the potential to host CRD mineralization within the underlaying Paleozoic limestones. The targets begin at roughly 150m and continue to 1,000m depth. The deepest silver-gold-lead mines in the district found in the base of the Bisbee Group in the Tombstone district typically are less than 200 meters below surface and still contain mineralization.
Positive indications for additional shallow, near surface epithermal mineralization at Tombstone include:
- Extensive gossanous mineralized north-south structures and thin bedding replacements (mini mantos/CRD’s) remain in both walls of the Contention north pit and the east wall of the central pit, rock chip samples collected in 2018 contain up to 23.5gpt Au (0.83opt) and 3,178gpt Ag (112.1 opt).
- A 1993 USMX report states their reverse circulation drilling in the Contention Pit outlined a near surface historic mineral resource of 1.15 million tons of 0.063 opt gold equivalent (1.7 gpt) which would now be considered high grade open pit material *see QP Statement
- Historic sample map of the floor of the south pit shows strong gold-silver mineralization that was never drilled
- New geological mapping identified prospective NS dikes/faults west of the Contention pit
- Historic geological section shows the Contention fault/dikes down dropped and repeated on the east wall of the north pit, and several times further east under cover
- Significant gossanous soil horizon along the west wall of all three Contention pits, suggesting buried oxide mineralization to the west
- New gold-silver mineralized rhyolitic quartz-feldspar porphyry intrusive found west of Contention Pit, opens-up area for exploration in interpretation
- Several encounters of native gold and silver chloride in the mineralization both in outcrops and in RC drill chips.
Positive indications for deeper, underground CRD mineralization at Tombstone include:
- The Bisbee sediments exhibit widespread fracturing, silica-limonite-sericite-clay alteration, oxidation and in the limey sediments, incipient hornfels and skarn development
- The Contention open pit mine appears to be hosted in the strongest NS structure which not coincidentally is occupied by rhyolitic to dacitic porphyry and mafic dikes possibly related to a deeper intrusion
- Intersections of NE veins, NW anticlinal folds, and the NS dikes are well known to produce high grade mantos within the lower Bisbee, greater than 95% of the Paleozoic section essentially virgin and un-explored
- The Contention underground mine was developed to a limited extent below the Bisbee Group following mineralization to 1,000 ft in depth
- Seven diamond drill holes of 2,100 to 3000 ft deep drilled by Santa Fe Gold in the west part of the district each intersected narrow high-grade CRD mantos, evidence that the Paleozoic limestones are prospective, for example 7.16m @ 6.5% Pb, 2.6% Zn, 0.61% Cu, 32 gpt Ag and 0.06gpt Au*
- The old Prompter Mine shaft and glory hole along the west side of the district show a strong and ancient WNW structure with low temperature manganese-quartz-calcite veins
- Several manganese-silver rich mines surround the Property and are indicative of distal mineralization to CRD deposits worldwide, as does zones of strong manganese oxide mineralization in the Bisbee within the Property
- The old Bunker Hill mine located in Paleozoic limestones south of the Bisbee basin and along the east extension of the Prompter Fault produced more tonnes than the old Contention mine, and was strongly polymetallic, again evidence that the Paleozoic limestones are prospective
A UVA magnetometer survey was flown in late 2018, results highlight the N-S dykes, a large granodiorite intrusive west of the property, and a subtle and broad NW trending magnetic high on the east side of the property. CRD’s don’t typically create magnetic highs but can be associated with and proximal to intrusive bodies (magnetic) similar to the setting at Tombstone.
*Aztec has not verified the historic drill results and is not relying on them
QP Statement – Allen David Heyl, B.Sc., CPG., is the Qualified Person for Aztec and has reviewed and approved the technical disclosures contained herein.