The Suitability of Stratiform Ore Deposits for the Narrow Reef Mining Equipment Method: Geological, Morphological, and Economic Criteria
Comparison of the NRE, Low Profile (LP), and conventional mining methods.
A simplified economic comparison was conducted between the Narrow Reef Equipment (NRE), conventional, and Low-Profile (LP) mining methods using data from the Unki Mine and NRE field trials. The analysis included only panel extraction activities (drilling, blasting, mucking, and ground support). While the NRE method had the highest monthly operating costs (416,300 USD), mainly due to ground support consumables and specialized equipment, it also achieved the highest productivity, ore recovery, and production value. NRE produced 10,642 t of ore per month with the lowest dilution, outperforming both LP (8,744 t/month) and conventional mining (2,026 t/month). Although LP had the lowest unit extraction cost (33 USD/t), NRE generated the highest monthly profit owing to superior ore recovery and higher grades. Conventional mining showed the lowest productivity and profitability. Sensitivity analyses demonstrated that mechanized methods, particularly NRE, are less affected by increases in labor costs and import tariffs than conventional mining. Overall, the results indicate that the NRE method is the most economically attractive option for the extraction of thin, sub-horizontal ore bodies.
The suitability of stratiform ore deposits for NRE is primarily controlled by ore-body morphology, which is governed by the genetic origin of mineralization. Thin, laterally continuous, and gently dipping ore bodies provide the most favorable conditions for NRE application, whereas thick, steeply dipping, or structurally disrupted deposits are generally unsuitable. Among the analyzed deposit types, reef-type PGE deposits and sediment-hosted stratiform copper and gold deposits show the highest compatibility with NRE, while contact and feeder-type Ni-Cu-(PGE), volcanogenic massive sulphide (VMS), and sedimentary-exhalative (SEDEX) deposits are largely unsuitable because of their irregular ore-body geometries. Local geological disturbances, including faulting, potholes, folding, and hydrothermal alteration, may reduce NRE suitability even within otherwise favorable deposits.
The proposed morphology-based scoring methodology is intended as an early-stage geological screening tool for identifying deposits with potential for NRE mining. Unlike multi-criteria decision-making approaches, it relies only on ore-body dip and thickness, avoiding subjective weighting and allowing consistent application across large datasets using publicly available geological information. Validation through the Unki Mine case study demonstrates that deposits classified as highly suitable for NRE also exhibit superior operational efficiency, lower dilution, improved ore recovery, and stronger economic performance compared with conventional and low-profile mining methods. Overall, the methodology provides a practical first-stage assessment that supports, but does not replace, detailed engineering, economic, and feasibility studies.