Probabilistic Resource Modeling of Vein Deposits

• Author / Creator

  Carvalho, Dhaniel

• Tabular vein deposits represent important projects and mining operations worldwide. Mining cost are high and are impacted by uncertainty in the geometry of the vein. Uncertainty can influence mine planning and operation. For this thesis, simple tabular vein structures with single or multiple stacked layers with gentle folds and disturbances are considered. There are many types of deposits that can be included in to this definition with different metals and commodities. Current techniques do not provide an assessment of the uncertainty in these types of deposits.
  Traditional and current workflows for mineral resource evaluation can be divided in the definition of the stationary domains, and the estimation or simulation of grades and properties. The estimation domains for tabular vein deposits are usually defined by explicit modeling, implicit modeling, or surface interpolation. These are deterministic methodologies that do not capture the geometry uncertainty as they generate a single vein solid.
  This thesis proposes a framework that captures geometric and other uncertainties, implements post-processing and sensitivity analysis to quantify vein resources uncertainty. The geometric uncertainty considers a local coordinates system, position and thickness uncertainty. The local coordinates system matches the vein geometry, grade and thickness modeling conform to the vein geometry, and anisotropy is modeled correctly. Position and thickness uncertainty from drill holes with shallow angle intersections are dealt with by imputing the geometric position perpendicular to the plane of continuity. Position and thickness distributions are calculated, merged, and sampled. Footwall and hangingwall surfaces are simulated using position and thickness values from imputation. Each realization has a different vein geometry. Other uncertainties are external boundaries and holes, grades, and parameter uncertainty. Fixing a single boundary for the vein is not realistic; multiple boundaries should be modeled. A different boundary is selected for each realization. Grades are usually modeled in regular grids that do not adapt to local variations in the vein geometry. An unstructured tetrahedron grid is used for grade simulation. The tetrahedron grid fits exactly the facet-based geometric model of the vein. Grades are simulated using different distributions realizations as input. Results from vein geometry and grade simulation can be summarized with post-processing and sensitivity analysis.
  Many aspects of mine planning, operation, resources reporting, and classification can be supported by these results. The major geostatistical concepts and techniques are reviewed. The proposed framework is explained with implementation details. Two case studies are presented: a single mineralized structure of gold vein deposit; a multiple layer silver vein. Results and discussion are presented.

• Subjects / Keywords

  • probability
  • resource estimation
  • vein
  • geostatistics
  • geology
  • modeling

• Graduation date

  Fall 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3MW28W7H

• License

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