Generation of High-Ni Sulfide and Alloy Phases During Serpentinization of Dunite in the Dumont Sill, Quebec
Bibliographic record
Abstract
The Dumont sill in the Abitibi region of Quebec is a zoned intrusive body which is differentiated into a lower ultramafic zone, composed of peridotite and dunite, overlain by a mafic zone, with clinopyroxenite, gabbro, and quartz gabbro subzones. Although the dunite contains several layers enriched in primary Ni sulfide minerals, which add considerable value to the deposit, 47% of the resource consists of awaruite- and heazlewoodite-bearing serpentinized dunites which formerly contained Ni only in silicate minerals. Serpentinization occurred isochemically with respect to major components, apart from the addition of H2O and minor loss of CaO. Serpentinization occurred under conditions of very low water-rock ratio, resulting in buffering of fluid to extremely low activities of silica and H2O and allowing the widespread replacement of primary pentlandite by awaruite and heazlewoodite due to accompanying reductions in f O2 and f S2. In layers containing primary accumulations of magmatic sulfide, serpentinization has resulted in the remobilization of nickel from olivine to enrich cumulus sulfides. In layers lacking primary sulfide accumulations, serpentinization was accompanied by the formation of awaruite by reduction of Ni originally hosted by olivine. Early stages of serpentinization were marked by the generation of large volumes of Fe-rich serpentine containing abundant ferric iron as well as lesser amounts of brucite rich in ferrous iron. Later stages of serpentinization caused the replacement of early iron-rich serpentine and brucite by more magnesian serpentine and brucite and the formation of abundant magnetite. Assemblages that are completely serpentinized contain lower nickel in silicates, higher nickel tenor sulfides, and more modal awaruite compared to those that are weakly and partially serpentinized, which are characterized by higher nickel in silicates and lower Ni tenor sulfides. Although awaruite first appears early in the serpentinization process, the highest modal abundances of economically extractable heazlewoodite, awaruite, and Ni-rich pentlandite are observed in rocks that have been completely transformed to the Mg serpentine facies. Regardless of the final opaque mineral host for Ni, the key to removal of Ni from silicate minerals and its sequestration in phases amenable to beneficiation is the early formation of awaruite; otherwise, Ni partitions readily into serpentine and remains inaccessible to mineral extraction. Exploration for similar deposits should be focused on dunite adcumulates formed from unfractionated komatiites, which have undergone complete serpentinization under conditions of diffusion-controlled low water-rock ratio, as evidenced by the absence of wholesale deformation or veining.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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 teacher head, 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".