Pathfinder Tonopah recently completed a PEA on the property that incorporates historically mined supergene copper resources and historic hypogene molybdenum-focused resources into a single mine project plan. Our process flow sheet uses known leaching technology in conjunction with flotation methods that yield viable copper recoveries and production of copper cathode and a molybdenum product. This flow sheet provides flexibility to transition from supergene copper resources into hypogene resources with only minor modifications to the process configuration.
Our project will produce copper cathode, which can be sold directly to markets, as well as molybdenum concentrate. There is an opportunity for the project to develop a facility that produces a higher-value molybdenum product on-site and potentially could serve
as a regional toll-processing facility.
The updated Mineral Resources are predominantly on private property, which offers opportunity for the first approximately 10 years of the mine plan to be exclusively on private ground and be permitted through Nevada state agencies. The site has in-tact facilities utilized by previous mine operators, including roads, power access, water-rights, office and maintenance buildings, and other infrastructure.
Pathfinder anticipates beginning work on a DFS that builds on a large body of technical studies already completed on most of the aspects of the project. Work programs for the DFS will refine facets of the project including pit-slope constraints, mine planning and fleet requirements, tailings and waste management, facility specifications, water monitoring and management, and metallurgical processes for supergene copper and hypogene molybdenum resources.
Pathfinder believes this project provides a unique opportunity to responsibly, efficiently, and expediently bring a copper project online in a favorable jurisdiction.
The Hall Mine Complex is centered on a porphyry Cu-Mo system in the western flanks of the San Antonio Mountains. The Hall Stock is a multi-phase, southeasterly plunging quartz monzonite porphyry (66-70 Ma) that hosts much of the Cu-Mo mineralization. The porphyry intrudes a metamorphosed package of Late Paleozoic to Early Mesozoic sediments that have been variably mineralized by the porphyry system. Tertiary dikes and volcanics cut the porphyry mineralization, and some of these later intrusive bodies appear to be associated with later, structurally controlled silver mineralization.
Basin and range faults cut portions of the system. One of the more prominent structures is the northerly striking Liberty Fault, which dips to the west at ~40° and truncates the porphyry system to the West, bringing mineralized basement rock up against basin-fill alluvium and colluvium. Uplift and weathering of the Cu-Mo porphyry system resulted in the development of a near-surface and near-horizontal supergene copper blanket.
Mineralization in the hypogene Cu-Mo porphyry is dominated by molybdenite (MoS2) and chalcopyrite (CuFeS2). The dominant copper mineral in the supergene blanket is chalcocite (Cu2S) with minor chalcopyrite.
The Complex was historically mined in the 1980’s and early 1990’s by Anaconda and later Cyprus for molybdenum, mainly within the hypogene porphyry system. In total, approximately 29 million tons of ore were processed to yield about 53 million pounds of molybdenum.
In the late 1990’s and early 2000’s, Equatorial Tonopah mined a portion of the supergene copper blanket, which was largely hosted in mineralized meta-sediments. Over 14 million tons of supergene ore were mined and heap leached.
Notes:
The updated Mineral Resource shows that the bulk of the known in-situ resources, both hypogene and supergene copper resources, remain unmined. Because portions of both the supergene and hypogene resources were mined historically, early phases of mining will require minimal development work, and we expect the strip ratio for the supergene copper resources over the first 10 years will be about 0.75:1.
The mine schedule and plan developed for the recently completed PEA is designed for a throughput of approximately 10 million tons of ore per year. At this production rate, the first 12 years of mining would focus on the supergene copper resources and produce over 463 million pounds of copper cathode. The PEA further considers the next 29 years of mining focused on the hypogene molybdenum resources, estimated to produce a total through the life of mine (41 years) of over 459 million pounds of molybdenum and over 633 million pounds of copper. Though the mine plan only considers 41 years of production to process about 404 million tons of ore, the Mineral Resource Estimate identified over 716 million tons of Measured and Indicated Resources, which illustrates the potential the project has for continued production.
Following results from tests completed with experts from three separate leading global firms, we have developed a metallurgical process flow sheet that recovers the best value from the copper and molybdenum utilizing both flotation and vat leaching. A bulk sulfide concentrate will be leached in a standard acid vat to extract soluble copper, which will be recovered as cathode. Residue from the leaching will be sent through cleaning circuits to recover molybdenum as a molybdenite concentrate. These well-known and effective processes will allow for treatment of both supergene and hypogene resources through the life of the mine retaining flexibility to blend resources with minimal modifications to the flow sheet. Once supergene resources have been depleted, the leaching circuits can be removed, and remaining circuits can be further optimized to recover molybdenum and hypogene copper for the rest of the mine life.
