The Muruntau gold mine in Uzbekistan is one of the largest gold mines in the world. The mine has an annual gold production of approximately 2 million ounces, and an estimated remaining gold inventory of over 1.5 billion ounces.
SRK Russia was contracted to prepare a mineral resource and ore reserve assessment of Muruntau, applying the JORC Code definitions and reporting standards. Although historical exploration and production information exists, the protocols applied to data collection differ from modern best practice.
Muruntau was explored by surface drilling and channel sampling from underground
workings. Exploration was performed according to the standard developed by
Geology Committee for Reserves (GKZ). The GKZ protocols were in place during
the collection, preparation and analysis of the historical samples, but only summary reports of the quality control sampling were obtained. Core from the historical drilling was also unavailable.
SRK employed an alternative approach to evaluate data quality, comparing the
grade control database to historical drilling and underground sampling campaigns. There were two parts to SRK’s approach. First, SRK used Leapfrog software to develop a grade control block model. This model produced estimates that aligned with production records. After this reconciliation, SRK formed pairs between the grade control samples and composites from the historical campaigns. Q-Q plots were a useful tool during statistical analysis, because these plots revealed biases related to particular grade ranges that may not be obvious from the summary statistics.
The historical summaries of QA/QC information and the comparison against grade control gave SRK confidence in the resource definition database to assign the Indicated classification that is a prerequisite for declaring ore reserves under the guidelines of the JORC Code.
In summary, grade control and reconciliation information can offer an alternative method of evaluating data quality, which may be appropriate when working with historical databases that do not fully comply with current expectations of QA/QC scope and detail.
