Fe‐Ni sulfides in Tagish Lake: Implications for nebular and parent body conditions of formation
Bibliographic record
Abstract
Abstract This study examined nine pristine samples representing seven lithologies of the ungrouped C2 carbonaceous chondrite Tagish Lake from the University of Alberta Meteorite Collection using scanning electron microscope and electron probe microanalyzer analyses to characterize the sulfide mineralogy, textures, and compositions present. Four distinct sulfide morphologies were identified including pyrrhotite containing exsolved pentlandite, unexsolved pyrrhotite, and unexsolved pentlandite, and a unique “bull’s‐eye” sulfide morphology. The at% Fe/Ni of the pyrrhotite grains within these samples decreases with increasing degree of alteration and roughly places them in the alteration order of TL11v chip1 < TL4 < TL11v chip2 < TL5b ≤ TL10a < TL 11h < TL1 < TL11i. The at% Fe/Ni of low Ni (<1 wt% Ni) pyrrhotite indicates that the overall degree of alteration of Tagish Lake lies between that of CM1/2 and CI chondrites. Comparison of the composition of the sulfides to established Fe‐Ni‐S phase diagrams at different temperatures indicates two separate generations of sulfide formation. They are (1) high‐temperature formation of exsolved pyrrhotite–pentlandite and much of the unexsolved pentlandite at ~500–600 °C, likely by cooling of a monosulfide solid solution melt during chondrule formation; and (2) low‐temperature formation of unexsolved pyrrhotite, some unexsolved pentlandite, pyrrhotite containing flame‐like pentlandite bodies, and bull’s‐eye sulfides at ~25–100 °C, likely formed during aqueous alteration events on the Tagish Lake parent body.
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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".