- Aztec is focused on discovery of high-grade Silver-Gold-Copper-Lead-Zinc CRD (carbonate replacement deposit) at Tombstone beneath historic mine workings that reached nominal depths of 500 feet (150m)
- 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 400 acres (162 hectares), 95% patented claims in the heart of Tombstone Mining District and Contention Pit
- High-grade near surface Silver-Gold epithermal vein potential never received modern exploration; dozens of veins never drill-tested
- Small disseminated Gold-Silver resource of 1.15M tons at 1.7gpt AuEq (non-43-101 compliant) is on property
- 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 1,000 meters (3,300 ft) of prospective Paleozoic limestone 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
- 23% of 139 rock chip samples contain >100gpt Silver, 17% >1.0gpt Gold, 24% >1.0% Lead, 16% > 1.0% Zinc, and 15% > 0.5% Copper
Aztec completed a Phase 1 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 silver-gold epithermal stock-works also cutting Bisbee Group, 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 the base of the Bisbee Group in the Tombstone district typically less than 150 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 silver-gold 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 rhyolite intrusive found west of Contention Pit, opens-up area for exploration in interpretation
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 dacite 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, 95% of the Paleozoic section essentially virgin and un-explored.
- The Contention underground mine was developed to a limited extent below the Bisbee Group chasing mineralization
- Seven 2,100 to 3000 ft deep Santa Fe drill holes 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
- 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 - Joey Wilkins, B.Sc., P.Geo., is the Qualified Person for Aztec and has reviewed and approved the technical disclosures contained herein. The mineral resource calculated by USMX Inc. in 1993 was done manually and incorporated a 45 degree pit slope and tonnage factor of 13 cubic feet/ton. They used silver to gold ratio of 28:1, $4.39 per ounce silver and $374 per ounce gold to calculate a gold equivalent. The mineral resource is a combination of 3 zones, the Contention, Tranquility, and Silverthread with a minimum strip ratio of 5:1. This is a historic mineral resource and the qualified person for Aztec has not done sufficient work to classify the historic resource as a current mineral resource. As a result, the Contention geologic mineral resource referred to is not being treated as a current mineral resource.