TITLE:
The Importance of Integrating Geological Mapping Information with Validated Assay Data for Generating Accurate Geological Wireframes in Orebody Modelling of Mineral Deposit in Mineral Resource Estimation: A Case Study in AngloGold Ashanti, Obuasi Mine
AUTHORS:
Joshua Wereko Opong, Chiri G. Amedjoe, Andy Asante, Matthew Coffie Wilson
KEYWORDS:
Mineral Resource Estimation, Geological Models, Sample Data, Validation, Assay Data, Geological Mapping
JOURNAL NAME:
International Journal of Geosciences,
Vol.13 No.6,
June
21,
2022
ABSTRACT: The basis of accurate mineral resource estimates is
to have a geological model which replicates the nature and style of the
orebody. Key inputs into the generation of a good geological model are the
sample data and mapping information. The Obuasi Mine sample data with a lot of
legacy issues were subjected to a robust validation process and integrated with mapping information to
generate an accurate geological orebody model for mineral resource estimation in
Block 8 Lower. Validation of the sample data focused on replacing missing
collar coordinates, missing assays, and correcting magnetic declination that
was used to convert the downhole surveys from true to
magnetic, fix missing lithology and finally assign confidence numbers to all the sample data. The
missing coordinates which were replaced ensured that the sample data plotted at
their correct location in space as intended from the planning stage. Magnetic
declination data, which
was maintained constant throughout all the years even though it changes every
year, was also corrected in the validation project. The corrected magnetic
declination ensured that the drillholes were plotted on their accurate
trajectory as per the planned azimuth and also reflected the true position of
the intercepted mineralized fissure(s)
which was previously not the case and marked a major blot in the modelling of the Obuasi orebody. The incorporation of mapped data
with the validated sample data in the wireframes resulted in a better
interpretation of the orebody. The updated mineral resource generated by
domaining quartz from the sulphides and compared with the old resource showed that the sulphide
tonnes in the old resource estimates were overestimated by 1% and the grade
overestimated by 8.5%.