Application of indicator kriging and conditional simulation in assessment of grade uncertainty in Hunters road magmatic sulphide nickel deposit in Zimbabwe
Date
2017
Authors
Chiwundura, Phillip
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Abstract
The assessment of local and spatial uncertainty associated with a
regionalised variable such as nickel grade at Hunters Road magmatic
sulphide deposit is one of the critical elements in the resource estimation.
The study focused on the application of Multiple Indicator Kriging (MIK) and
Sequential Gaussian Simulation (SGS) in the estimation of recoverable
resources and the assessment of grade uncertainty at Hunters Road’s
Western orebody. The Hunters Road Western orebody was divided into two
domains namely the Eastern and the Western domains and was evaluated
based on 172 drill holes. MIK and SGS were performed using Datamine
Studio RM module. The combined Mineral Resources estimate for the
Western orebody at a cut-off grade of 0.40%Ni is 32.30Mt at an average
grade of 0.57%Ni, equivalent to 183kt of contained nickel metal. SGS
results indicated low uncertainty associated with Hunters Road nickel
project with 90% probability of an average true grade above cut-off, lying
within +/-3% of the estimated block grade. The estimate of the mean based
on SGS was 0.55%Ni and 0.57% Ni for the Western and Eastern domains
respectively. MIK results were highly comparable with SGS E-type
estimates while the most recent Ordinary Kriging (OK) based estimates by
BNC dated May 2006, overstated the resources tonnage and
underestimated the grade compared to the MIK estimates. It was concluded
that MIK produced better estimates of recoverable resources than OK.
However, since only E-type estimates were produced by MIK, post
processing of “composite” conditional cumulative distribution function (ccdf)
results using a relevant change of support algorithm such as affine
correction is recommended. Although SGS produced a good measure of
uncertainty around nickel grades, post processing of realisations using a
different software such as Isatis has been recommended together with
combined simulation of both grade and tonnage.
Description
A research project report submitted to the Faculty of Engineering and the Built
Environment, University of the Witwatersrand, in fulfilment of the requirements
for the degree of Masters of Science in Engineering, 2017
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Citation
Chiwundura, Phillip (2017) Application of indicator kriging and conditional simulation assessment of grade uncertainty in Hunters road magmatic sulphide nickel deposit in Zimbabwe,University of the Witwatersrand, <https://hdl.handle.net/10539/24082>