Some literatute about keyhole mining technique and its advantages (extracts are from Google):
What is In-situ recovery (simply put keyhole mining method)?
In-situ recovery (ISR, also referred to as in-situ leaching or solution mining) may offer such a step-change approach. ISR refers to the recovery of valuable metals from ore deposits by the circulation of a fluid underground and the recovery of the valuable metal from the fluid at the surface for further processing. It has the potential to be a low-impact and selective mining option, almost the equivalent to keyhole surgery for humans.
The significant economic advantages of ISR compared with other mining methods are that it eliminates or reduces mining costs significantly by avoiding the removal of ore and overburden to surface dumps, stockpiles or operations; avoids comminution costs required prior to beneficiation, flotation or leaching and the associated issues of generation and storage/disposal of tailings. These advantages could allow for currently sub-economic ores to become attractive, for example, by avoiding significant upfront capital and ongoing operating costs. There will, of course, be costs associated with ISR operations. For example, wellfields must be developed, sub-surface access creation may be required and solutions will need to be pumped underground and back to the sISR offers additional advantages in that such an approach could avoid the creation of pits, dumps and tailings dams. Other improved health, safety and environmental outcomes would include the removal of people from underground; a reduction in dust, noise, greenhouse-gas emissions, seismic events and surface footprint; and landslides, deforestation, erosion and siltation, which ensures value extraction without the typical legacy.urface for further processing.Reduced remediation and rehabilitation requirements, and therefore, reduced mine-closure costs make ISR technology attractive in that much of the restoration of surface aesthetics, as related to conventional processing routes, is not required. In addition, energy, water and the greenhouse gas footprint of many mining projects could have been improved significantly if an ISR approach had been adopted.This type of approach could enable company conversion from an “explorer” to an “owner/operator” with a much smaller capital barrier and provide potential additional opportunities in the METS sector in the design, manufacture and operation of small mobile modular plants. Contract operators could be employed to run the modular plant.
It is even possible that such plants could be leased for processing by different companies in different areas. ISR could also extend mine life and associated jobs and/or increase the target value for existing operations. Closed or closing mines could be revisited for additional value recovery. For example, residual values in pit floors or walls, in low-grade areas adjacent to or between pits, underground and stranded between valuable mineralised zones or small or remote ore bodies may be profitably recovered to process by ISR means.
It may also be possible to progress projects where a political or social risk may not justify a traditional large capital investment. ISR would particularly benefit those deposits that would require cooling before conventional extraction could proceed, as accelerated ISR extraction would exploit the favourable leach kinetics. Besides temperature, pressure may also provide advantages for accelerated leach recoveries and favourably change solution chemistry.
This type of underground mining method is only severl years old (as mentioned in CTO's latest/last ASX release).
Perhap's there's "ight at the end of the tunnel". Stay tuned for the next four months.....
(20min delay)