Geostatistics and Sample Numbers from an Acid and Metalliferous Drainage Perspective

Danny Kentwell, Andrew Garvie and Claire Linklater
Wednesday, October 12, 2016
First presented: 
AusIMM Life-of-Mine Conference, 28-30 September, 2016

Various Australian and international regulatory bodies (Environmental Protection Authority, 2015) require an early assessment of the geochemistry of waste rock. This usually includes estimates of the locations and volumes of potentially acid-forming (PAF) materials and requires sampling of the waste rock zones as well as submitting the samples for a series of tests. We know that the required number of samples will vary depending on rock type, mean sulfur levels and spatial variability of sulfur as well as total volume. The key question is how do we know when we have enough samples?

This extended abstract describes the application of geostatistical methods to examine how sample numbers and sample locations influence the preliminary conclusions that may be drawn for early stage waste characterisation.

Feature Author

Danny Kentwell

Danny Kentwell is a geostatistician with a background in geological modelling, mine planning and surveying. He has 25 years’ international experience with varied commodities including gold, copper, mineral sands, iron ore, nickel laterites, nickel sulphides and phosphate. Danny’s skills cover, 3D modelling, Resource estimation, open pit optimisation scheduling and design. His geostatistical expertise includes standard and recoverable resource estimation techniques such as uniform conditioning, indicator kriging and conditional simulation as well as multivariate estimation and simulation. As a geostatistician and engineer, he has an excellent understanding of the advantages and limitations of different resource estimation techniques, their resulting block grade, tonnage and value curves and their use in mine planning. Danny also has experience in applying geostatistical techniques to waste characterisation and determination of sampling adequacy from very small data sets.

Principal Consultant (Geostatistics)
MSc (Mathematics & Planning; Geostatistics), FAusIMM
SRK Melbourne
Andrew Garvie

Andrew Garvie has more than 24 years’ experience providing scientific and technical assessments in acid and metalliferous drainage (AMD) and heap leach oxidation.  More recently he has undertaken assessments of self-heating and the potential for spontaneous combustion of coal wastes and carbonaceous black shales associated with sulfide minerals.  Studies have included the quantification of physical processes that support the oxidation of mine wastes and heap leach piles by measurement and predictive modelling.  He has assessed strategies used at mines to control oxygen supply and water flux into dumps and heap leach piles using the same methods.  Andrew’s experience includes use of geostatistics to assess the adequacy of sampling, geochemical characterisation to examine the potential of mine wastes to produce AMD, and assessment of contributors to pit lake water quality, including wall rock oxidation and in-pit waste rock disposal.  He has applied his understanding of the above processes to the development of conceptual waste landform closure strategies for the control of AMD production and spontaneous combustion.

Principal Consultant (Geoenvironmental)
PhD (Physics), MAusIMM
SRK Sydney
Claire Linklater

Claire Linklater has 22 years’ experience in interpretation of geochemical data, building conceptual models of processes which control in situ geochemical behaviour and the application of geochemical modelling codes.  Her early career was focused on management of radioactive wastes; understanding and quantifying the geochemical behaviour and mobility of radionuclides in the ‘geosphere’ surrounding a proposed underground repository and assessing the long-term stability of engineered and natural barriers.  More recently, she has focused on sulfidic materials management: acid/alkaline rock drainage (ARD) assessment and prediction; water quality and pollutant mobility from waste rock dumps, tailings storage facilities, underground workings and pit walls; assessing the effectiveness of potential mine closure strategies.

Principal Consultant (Geochemistry)
PhD (Geology), FGS, FAusIMM
SRK Sydney
SRK Worldwide