Selenium Distribution in the Gossan of a Porphyry Copper Deposit, Red Chris Mine, British Columbia, Canada
Bibliographic record
Abstract
Abstract In 2015, the Red Chris mine in northwestern British Columbia began processing near-surface ores from the Red Chris copper-gold deposit and encountered higher leachable selenium concentrations in process water than had been anticipated from testing of deeper ores. Samples of gossan, near-surface rock, and deeper hypogene rock were submitted for analytical, mineralogical, and kinetic geochemical testing to investigate the origin of the leachable selenium, its mineralogical form, and the release mechanisms. This paper presents testing results and implications for understanding the selenium distribution in weathered rocks at sulfide mineral deposits. Shallow weathered rock, including the gossan, contained higher selenium concentrations and higher ratios of selenium to sulfur relative to the hypogene bedrock. Laboratory weathering and leaching tests indicated that selenium is released from source sulfides by oxidation and retained in a variety of secondary mineral forms. Mean selenium content in the solids was measured as follows: gossan and shallow bedrock >> deeper near-surface bedrock > hypogene bedrock. Water-leachable selenium varied but generally followed a similar trend, with samples of gossan containing the highest water-leachable selenium. Selenium was determined to be preferentially leached from the gossan samples at high pH values, indicating an adsorbed form. We propose that the weathering profile of the Red Chris deposit was previously capped with a well-developed thick gossan, which formed during the Paleogene and was eroded during the last period of glaciation. The current weathered rock reflects the residual base of the former oxidized profile.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 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".