Using Trace Elements in Chromites to Constrain the Origin of Podiform Chromitites in the Thetford Mines Ophiolite, Quebec, Canada
Bibliographic record
Abstract
The Thetford Mines Ophiolite is interpreted as a fragment of a fore-arc oceanic lithosphere. This complete ophiolitic sequence consists of a thick mantle sequence, a plutonic crustal component, and a volcano-sedimentary sequence dominated by boninitic lavas. One third of its 50 chromitite occurrences are podiform and are hosted in a dunitic envelop within the mantle tectonites. \nThis study presents the concentrations of a complete suite of minor and trace elements (Sc, Ti, V, Mn, Co, Ni, Zn, and Ga) in chromites from podiform chromitites of the Thetford Mines Ophiolite (Canadian Appalachians) and from the associated boninite lavas, using laser ablation inductively coupled to a plasmaquadrupole mass spectrometer. \nThe chromites from Thetford Mines Ophiolite podiform chromitite deposits are Cr rich (Cr# = 100*Cr/(Cr + Al) = 69–84), Ti poor (TiO2= 0.06–0.18 wt %), Ga poor (13–26.5 ppm), Ni poor (441–875 ppm) and are similar to chromite in boninites from around the world and to the chromites in the boninite lavas of the Thetford Mines Ophiolite. The Al/Ti ratios of the chromites have been used to determine the nature of the melts from which podiform chromitites in the Thetford Mines Ophiolite have crystallized. These have been found to resemble closely the boninites capping the crust of the ophiolite. The empirical partition coefficients for minor and trace elements (Sc, Ti, V, Mn, Co, Ni, Zn, and Ga) in chromite calculated from the chromite and their host lava (boninite and MORB) compositions are similar to experimentally determined values.
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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 | 0.001 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".