34 In the Field or in the Lab: Revealing Hidden Signals from Minerals

Tuesday, 16 April 2024
8:00 AM - 12:00 PM
Swannanoa

IMPROVING RESOURCE MODELS WITH RECURSIVE PARTITIONING FOR DOMAIN DEFINITION: CASE STUDY OF MnCO3 AT NSUTA, SOUTHWESTERN GHANA

Paper number: 34-10
Program: Theme Sessions
Time: 10:45 AM – 11:05 AM

Authors

Abstract

This presentation describes the use of Recursive Partitioning (RP) to support the creation of domains for resource estimation at the Nsuta manganese carbonate deposit in southwestern Ghana. The geological database in conjunction with the assay data was used to create a recursive partitioning tree that identifies the geological criteria that best separate mineralized intervals. The terminal nodes in this decision tree were then coded as indicators, 0s for weakly mineralized and 1s for strongly mineralized. Following analysis of the spatial continuity of the indicators, an inverse distance interpolation was used to estimate the probability of strong mineralization, guided by the indicator variogram analysis. A threshold level for the probabilities was then chosen to partition the block model into two domains for resource estimation.

The advantage of this approach over more conventional methods is twofold. First, it avoids the direct use of grade data as the basis for creating estimation domains. Many authors have previously recognized the shortcomings of this “grade zone” approach, which risks over-estimation.

The second advantage of this approach is that RP can construct domains that do not depend on a single geological criterion. The use of RP allows one to create indicators that are based on several geological factors unique from the conventional method.

The recursive partition analysis confirmed the barren and the ore materials. The presentation discusses the data cleaning and analysis (QA/QC) necessary as a first step. It shows how commercial software was used to do the RP analysis, and to code indicators into the data files. It discusses the calculation of probabilities, the checking of the appropriate threshold for partitioning the deposit into domains, and the use of customized software to convert the block model partition into DXF wireframes needed by the software that performs the final resource estimation. Resource estimation was done by ordinary kriging and checked by inverse distance interpolation, with the two methods coming within 5% of each other on tonnage and grade.

Keywords: Recursive partitioning, resource estimation, domaining

Geological Society of America Abstracts with Programs. Vol. 56, No. 2

doi: 10.1130/abs/2024SE-396915

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