The use of Conditional Simulation for Drill Hole Spacing Evaluation and Decision-Making in Telégrafo Project, Northern Chile

摘要

The Telégrafo copper – gold deposit is located in the Centinela district of the Antofagasta region inrnnorthern Chile. Telégrafo is a porphyry copper deposit of Eocene – Oligocene age which has a totalrnmineral resource in measured, indicated and inferred categories equal to 2.6 billion tonnes with anrnaverage grade of 0.38 per cent copper.rnCurrently the project is in the prefeasibility study phase, including an infi ll drilling campaignrnto improve the knowledge of the deposit that should result in an improvement of the mineralrnresource classifi cation. In this context was decided to review the classifi cation criteria in order tornoptimise the drill hole density necessary to support the project.rnThis paper presents an application of conditional simulation to evaluate the risk related to drillrnhole spacing, using a geostatistical approach that mimics the process of evaluation of resourcesrnfrom the perspective of geological modelling and grade estimation.rnThe fi rst step of the approach is the generation of conditional simulations using the availablernsamples to generate several plausible scenarios of the deposit in terms of copper grades andrngeological units. These scenarios are considered as the unknown reality of the deposit and sampledrnby synthetic drill holes in order to replicate the geological model process and copper resourcernestimation.rnIn this way it is possible to establish differences between the possible scenarios and the generatedrnresource estimation models for several simulated drill hole spacing alternatives. These differencesrnor errors can then be quantifi ed in terms of estimated mean, metal content and tonnage overrndifferent production volumes.rnThe resulting errors were useful in assisting the decision making process related to the design ofrndrill hole spacing for each category of mineral resource in the Telégrafo project, and to redistributernthe budget associated to the drill campaigns for the next stage of the project.