Characterization of the REE fluorocarbonate minerals and REE release at Earth’s surface conditions of the T-Zone of the Nechalacho Deposit, Northwest Territories, Canada
Bibliographic record
Abstract
There is limited knowledge regarding the behaviour of naturally occurring bastnaesite [REE(CO3)F] and parisite [Ca(REE)2(CO3)F2] during mineral-fluid interaction. Bastnaesite and parisite comprise the rare earth element (REE) ore of the T-Zone at the Nechalacho Deposit, located in the Northwest Territories, Canada. This study characterizes the bastnaesite and parisite at this location and investigates the dissolution rates of bastnaesite and parisite at near Earth’s surface conditions. Analysis of the ore minerals of the T-Zone by electron microprobe analysis (EMPA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), indicated that the minerals are enriched in light rare earth elements (LREE). Bastnaesite and parisite are intergrown with each other and with fluorite and quartz as determined by scanning electron microscopy (SEM). Batch dissolution experiments were performed with a mixture of bastnaesite, parisite, fluorite and quartz in water to evaluate the effects of pH and grain size on the solubility of the REE minerals. Experiments were run at pH 2, 4 and 9 with three differing starting percentages of bastnaesite, parisite, quartz and fluorite. The dissolution of bastnaesite and parisite is largely pH dependent, with more REE released at acidic conditions than at alkaline conditions. In pH 2 conditions, precipitation of a lanthanide (Ln) fluoride phase is evident through X-ray diffraction (XRD) and SEM analysis. At an initial pH 4, the solution was neutralized within ~60 h to a pH of 7-8, exhibiting that bastnaesite and parisite can neutralize moderately acidic solutions but not highly acidic (pH 2) solutions. Mixed flow through dissolution experiments containing bastnaesite, parisite and quartz were performed at pH 2, 4 and 8.6 conditions. Results revealed that at pH 8.6 the release rate of total REE and Ca is likely non-stoichiometric whereas the release rate of total REEs and Ca at pH 4 is closer to stoichiometric. Formation of LnF3 was evident at pH 2, illustrating the ready dissolution of bastnaesite or parisite followed by the rapid precipitation of LnF3 at low pH. Dissolution rates increased as a function of decreasing pH and were slower than calcite dissolution at the same pH conditions.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".