Implications of Non-Acid Metal Leaching on Mine Rock Management at a Nickel Mine in Permafrost Terrain:1 – Mine Rock Evaluation
Bibliographic record
Abstract
Raglan is a nickel-copper-cobalt mine in the continuous permafrost region of Quebec. The management plan for waste rock at the mine was developed during the Environmental Assessment stage of the project and was based on acid based accounting (ABA) methods to identify acid generating and non-acid rock types with the intent to backfill the open pits and freeze the acid waste. The screening criteria were reexamined in 1999 to address nickel leaching and to develop more conservative and lower risk criteria than the ABA approach. A waste rock assessment study was initiated to focus on nickel leaching at neutral pH. The major rock types were characterized and humidity cell tests were established with regular distilled water and with pH adjusted (acetic acid to pH<7) water to determine nickel release rates from these materials. The results showed that the waste rock solids exhibited high nickel to sulphur ratios that likely reflected traces of pentlandite sulphur in contrast to the more usual pyrrhotite sulphur in similar waste rock. Nickel leaching was evident for most rock types even when the sulphur contents in the rock were as low as 0.3%. In contrast to other studies that exhibited lag times of tens of weeks to observe nickel leaching, the absence of buffering above pH values of 8 in the Raglan materials resulted in nickel leaching within a few weeks of initiating the humidity cell tests. It was found that nickel leaching at neutral pH and not acid generation was the defining criteria for waste rock that required additional management. As a result, a significant decision was made to alter the mine plans and to revise the baseline assessment of the proposed mining areas as described in a companion paper (Nicholson et al., 2003).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".