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MDAG.com: Online Since 1997
Providing Valuable Technical
Information on Minesite Drainage,
and on the Environmental Geochemistry
of Highly Reactive Geologic Materials
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The latest MDAG Case Study 82 is: The Meaning and Complexity of pH "Plateaus", like pH 3.0 to 3.7 for Fe-OH Minerals, during Neutralization along Flowpaths.
This MDAG Case Study is about pH plateaus (originally called geochemical “sub-regions”) during the neutralization of acid rock drainage (ARD) along flowpaths. This Case Study shows how recent documents like the INAP GARD Guide fail to identify the original source of these pH plateaus and fail to accurately describe the meaning and complexity of the plateaus. Tracing backwards through older documents confirms the original source of pH plateaus, which provides information on the true complexities and provides the detailed explanation, simulation, and application to full-scale ARD of these plateaus and sub-regions.
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MDAG Case Studies #80 and #81 are:
#81: The Complex Nexus of Sulphide Oxidation, Silicate-Mineral Dissolution, and Passive CO2 Capture
#80: Silicate Neutralization Potential Focussing on Plagioclase,
and the MDAG Silicate NP Model
The spreadsheet-based
MDAG Silicate NP Model (~150 kb,
Version 2024.02) can be downloaded for free here.
There is a small percentage of minesites where Silicate NP (Neutralization
Potential) is much more important than Carbonate NP for assessment and predictions of acid rock
drainage (ARD). They are at the nexus of three interacting geochemical processes:
(1) sulphide oxidation and acidity generation,
(2) the rapid dissolution of neutralizing, calcium-bearing silicate minerals, particularly calcium-bearing plagioclase minerals, and
(3) the passive capture of atmospheric CO2.
The relative importance of silicate NP can be signified by site characteristics like (1) typical acid-base accounting (ABA)
predicts substantial ARD but none is detected, and (2) no ARD is detected on the full scale while smaller-scale kinetic testwork releases ARD
within years. Based on past studies and one recent study, these MDAG Case Studies formulate an approach for
more reliably assessing Slow-Neutralizing
Silicate NP and Fast-Neutralizing Silicate NP with a focus on plagioclase minerals. Fast-Neutralizing NP is then combined with Carbonate NP to obtain
the most relevant, effective Total NP. The intensity and types of testwork and studies needed to understand silicate neutralization on a site-specific basis,
and the reasons for the failure of typical ABA, are highlighted.
Note: These Case
Studies provide supporting information for a paper published by and presented at ICARD 2024, entitled "Predictions of ARD Potential Dominated by Silicate Neutralization Potential at the Troilus Gold-Copper Minesite, Québec, Canada".
A draft version of this paper with additional figures and tables
not in the final version is available
here.
An expanded version of the PowerPoint presentation with additional figures, tables, and explanations not in the final version is available
here. Additional presentations and explanations can be found
here and
here,
including the
presentation at the BC MEND 2024 31st Annual Workshop.
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Five technical books on minesite drainage and highly reactive geologic materials are available here at MDAG.com, free of charge.
1) Wavelet Transforms of Drainage from Highly Reactive Geologic Materials; ISBN 978-0-9952149-3-4
2) Searching for Latent Variables in Minesite Drainage Using Exploratory Factor Analysis; ISBN 978-0-9952149-2-7
3) Spectral Analysis of Drainage from Highly Reactive Geologic Materials; ISBN 978-0-9952149-1-0
4) Environmental Geochemistry of Minesite Drainage: Practical Theory and Case Studies; ISBN 0-9682039-1-4
5) Minesite Drainage Chemistry: An Introduction; ISBN 978-0-9952149-0-3
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We have also published and co-published more than 100 informative documents at
conferences and in journals.
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Adverse environmental effects can arise from water draining over and through highly reactive materials,
such as mining wastes. We steadfastly believe that these adverse effects can
only be understood, predicted, moderated, and remediated reliably by thoroughly understanding past
competent work and by carefully studying full-scale sites.
Heed the
old words of wisdom "Those who ignore the past are doomed to repeat it"
or perhaps some newer ones "we learn from the mistakes of the past how to make new ones".
Is that why we hear that up to 90% of predictions of minesite-drainage chemistry
are too low,
and remain too low for newer minesites, leading to
unexpected costs and
adverse environmental effects for mining
companies and taxpayers? The public is starting to pay closer attention to these errors
and unexpected costs, with mining companies losing credibility. This
is why we at MDAG heavily emphasize real case studies
with abundant data, followed by theory and modelling in subordinate roles.
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site!
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Created by K. Morin