In early 2012 Montero Mining and Exploration Ltd contacted Maptek to conduct resource estimation work for their Wigu Hill property in Tanzania. Montero needed a detailed study of the project to increase the resource.
Maptek provided Montero with an improved constrained resource block model, a grade and tonnage report, and a CSV resource block model compatible with mine planning software. This gave Montero the information they needed for mine design and optimisation, and to create a base scenario schedule to move the project forward.
Maptek worked with drillhole and trench data provided in Microsoft Access® databases. A geological model was built and a resource was calculated using grade estimation tools in Vulcan.
The Wigu Hill property is a large, rare earth element (REE) enriched carbonatite hosted in a dolomitic vein/dyke system that cuts into Precambrian gneisses. The coarse-grained carbonatite dykes largely contain dolomite, calcite, bastnaesite and quartz.
REE mineralisation is concentrated in these carbonatite dykes. The REEs occur predominantly in the bastnaesite, monazite and synchysite, with some parisite and goyazite.
The study was carried out on the Twiga target. The area was drilled and trenched; grab samples were taken. Fourteen diamond drillholes were drilled for 1465 metres.
Initially a non-constrained block model was used to understand grade continuity within the samples.
Statistics were then run on the drillhole database to create composites identifying grades above a set cut-off to generate triangulation sections.
Maptek also created solid models from CBA (bastnaesite bearing carbonatite) sectional interpolation maps received from Montero Mining. Comparison was made on the CBA section model, total REE model and grade shell model to verify continuity.
The estimation work was done within the final Vulcan model with user defined estimation parameters.
From the solid orebody model, a resource block model was created. Nine elements were estimated: total rare earth, lanthanum, cerium, neodymium, praseodymium, samarium, uranium, thorium and strontium oxide.
The estimation was limited to the interpreted modelled carbonatite orebody. Grade estimates were calculated in Vulcan using inverse distance estimation. User-defined parameters included block model sizes, search ellipsoid orientation and search distances.
The Vulcan advanced reserves editor was applied to calculate reserves on the block model. A cut-off of 4% was selected for the main Tree_ivd variable, and the reserves report was based on this cut-off grade.
Maptek then provided an improved detailed block model comparing results to the previous work on the Wigu Hill area. The final report produced an improved grade tonnage of the REE resource.
Montero Mining and Exploration Ltd
Presented at 2012 North America Users Conference