The technical report explicitly states that recovery methods for the Van Dyke Copper Project are “Not Applicable” in Section 17, indicating that no active processing or recovery methods were being implemented at the time of the report. However, the document provides contextual insights into historical and adjacent operations that may inform potential future recovery approaches for the Van Dyke deposit.
Historical and Adjacent Recovery Methods
1. In-Situ Leaching (ISL):
– The adjacent Miami Unit (BHP Copper, Inc.) historically employed ISL after underground mining ceased in 1959. The method involved leaching copper from the block-caved underground mine and reprocessing historical tailings via hydraulic mining. Operations were discontinued in 2001, with only limited production thereafter.
– The Inspiration Mine (Freeport McMoRan) utilized solution extraction/electrowinning (SX/EW) for leaching, alongside a smelter and rod mill processing cathodes from other Arizona mines.
2. Regional ISL Practices:
– Arizona has hosted multiple ISL projects, including the Pinto Valley, Miami-East, and San Manuel mines, which combined ISL with conventional mining.
– The Florence Copper Project (Taseko Mines Ltd.), 65 km southwest of Van Dyke, is a pilot-scale ISL operation with 24 injection/recovery wells and an SX/EW plant, focusing on environmentally safe copper recovery.
3. Van Dyke’s Historical ISL Tests:
– Phase 1 & 2 ISL tests (Occidental, 1981–1988) and later work by Kocide (1990) are referenced, though specifics on technical parameters (e.g., lixiviant composition, well spacing, recovery rates) are not detailed in this report.
Technical and Operational Context
– Mineralization: The Van Dyke deposit lies within the Miami-Inspiration trend, characterized by supergene chalcocite and oxide copper zones in fractured Proterozoic schist and Tertiary granite.
– Infrastructure: Historic infrastructure includes a cementation plant, drill sites, and the Van Dyke Shaft, though no active processing facilities exist.
– Challenges:
– Environmental Liabilities: Legacy drill sites and leaching infrastructure (pre-1990) pose unresolved risks.
– Data Gaps: The 2019 re-sampling program (2,193 new assays for TCu, ASCu, CNCU) improved resource confidence, but deposit geometry may evolve with further exploration.
Innovation and Future Potential
– The report hints at ISL as a plausible future method, given its success in adjacent deposits and regional projects like Florence Copper. However, no throughput, recovery efficiencies, or equipment specifications are provided for Van Dyke.
Conclusion
While the report lacks direct details on Van Dyke’s processing circuit, it underscores the deposit’s compatibility with ISL/SX-EW methods, drawing parallels to neighboring operations. Key hurdles include environmental remediation and further geological delineation before selecting a recovery strategy.
