7th ICARD 2006 Abstract Submission (Rayne and Connell, v1) .pdf
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Title: Abstract Submission for the 7th International Conference on Aci
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Abstract Submission for the 7th International Conference on Acid Rock Drainage
Type of Presentation: Oral
Subject Area(s): Case Studies: Lessons Learned; Closure/Land Use Issues
Environmental Geochemistry of Canadian Kimberlites:
A Review of the Impacts on Current and Proposed Mining Activities
Sierra Rayne* and Larry Connell
AMEC Earth & Environmental
2227 Douglas Road
Burnaby, British Columbia, Canada, V5C 5A9
* Presenting and corresponding author: E-mail: email@example.com; Telephone: +1
(604) 294 3811; FAX: +1 (604) 294 4664
Raw and waste kimberlitic materials are generally thought to be relatively
environmentally benign, producing drainage with elevated metal loadings from some
elements (e.g., Al, Ni, Co, Sr, Zn) and little potential for net acid generation. However,
recently published experience at the operational Ekati and Diavik Diamond Mines in
northern Canada suggests the potential for water quality issues due to the production of
high total dissolved solids (TDS) loadings from kimberlite storage and disposal areas
(e.g., TDS up to and >5,000-10,000 mg/L). High TDS loadings to receiving waters are of
concern due to potential toxicological effects, and the lack of economically feasible TDS
treatment technologies (e.g., reverse osmosis, distillation) in the remote locations where
diamond mines in Canada are located.
Supporting these field observations for TDS at Ekati and Diavik are current geochemical
testing results for the proposed Jericho 1, Victor 2, Snap Lake 3, and Gahcho Kué 4
diamond projects. Kimberlitic effluents from field data at the operational sites and testing
procedures at planned mines contain high concentrations of chloride, sulfate, calcium,
magnesium, and sodium in source-dependent relative proportions according to sitespecific mineralogy. The high reactivity of kimberlite may also result in localized saline
groundwater chemistry gradients near the kimberlite pipes/dykes 5 that also requires
consideration in hydrologeological modeling of inflows to open pits and underground
works, and subsequent surface water quality modeling and water management planning
Kimberlites may also pose unique challenges in terms of predicting and managing the
long-term pH of their drainage, with implications for increased weathering of TDS
components. The presence of significant amount of alkaline minerals (e.g., calcite and
dolomite) in the kimberlite yields neutralization potentials (NPs) typically »20 kg
CaCO3/tonne. Combined with sulfide contents generally <0.3% by weight, it is typically
thought that kimberlites pose little risk for acid-rock drainage (ARD). The high net
neutralizing potentials (NNPs; typically >20 kg CaCO3/tonne) and neutralization potential
ratios (NPRs; typically »10) from static acid-base accounting (ABA) tests on kimberlite
support these preliminary assessments. As such, current concerns regarding kimberlitic
drainage are typically related to short- through long-term alkaline (pH>9) drainage that
may require management.
However, kinetic testing results suggest that, in some kimberlitic units, NP is weathered
more rapidly than sulfides. This phenomenon results in short- through medium-term
alkaline drainage (often pH >8-9), but in the long-term, kimberlite may subsequently
become net acid generating due to the presence of residual, unweathered sulfides after
the substantial initial NP content has been depleted. This may lead to the unusual
scenario of a waste rock unit changing from alkaline to acidic drainage following mine
closure, thereby requiring adaptive management and treatment methodologies to best
address any environmental concerns. Furthermore, the future onset of kimberlitic ARD
may increase TDS and metal loadings from this lithology, which may require
consideration in long-term post-closure water quality predictions.
Lytton Minerals, Ltd. Jericho Project: Evaluation of JD/01 Tailings Geochemistry. Tahera
Corporation, July 1998; SRK Consulting. Technical Memoradum H – Supplemental Geochemistry:
Jericho Project, Nunavut. Tahera Corporation, October 2003; SRK Consulting. Technical Memoradum
I – Estimates of Source Concentrations: Jericho Project, Nunavut. Tahera Corporation, October 2003;
AMEC Earth & Environmental. Review of Total Dissolved Solids in Proposed Discharge from the
Jericho Diamond Project: West Kitikmeot, Nunavut. Tahera Corporation, June 2004.
SRK Consulting. Summary of Geochemical Characterization and Water Quality Estimates: Victor
Diamond Project. De Beers Canada, Inc., October 2003.; AMEC Earth & Environmental. Processed
Kimberlite Containment Facility Feasibility Design Report: Victor Diamond Project Feasibility Study,
Attawapiskat, Ontario. De Beers Canada, Inc., February 2004.
Golder Associates. Geochemistry Report (Appendix III.2): Snap Lake Diamond Project. De Beers
Canada, Inc., February 2002.
AMEC Earth & Environmental. Acid-Base Accounting Results: Kimberlite Ore Samples. De Beers
Canada, Inc., October 2004.; AMEC Earth & Environmental. Shake Flask Testing Results: Kimberlite
Ore Samples. De Beers Canada, Inc., November 2004.; AMEC Earth & Environmental. Humidity Cell
Kinetic Testing Results: Kimberlite Ore Samples. De Beers Canada, Inc., January 2005.
Borisov, V.N., Alexeev, S.V., and Pleshevenkova, V.A. The diamond mining quarries of East Siberia
as a factor affecting surficial water quality. In: Water-Rock Interaction. Eds.: Kharaka, K.K., Chudaev,
O.V., Thordsen, J.J., Armannsson, H., Breit, G.N., Evans, W.C., Keith, T.E.C., and Khakara, Y.K.
Balkema: Rotterdam, The Netherlands, pp. 863-866.; Sader, J.A., Leybourne, M.I., McClenaghan,
M.B., Hamilton, S.B., and Robertson, K. Field procedures and results of groundwater sampling in
kimberlite from drillholes in the Kirkland Lake and Lake Timiskaming areas, northeastern Ontario.
Geological Survey of Canada: Current Research, 2003-C11, pp. 1-9.