Mantle metal mobility: preliminary gold and platinum group element geochemical results
Bibliographic record
Abstract
Mantle sulphides are rare but relatively important mineral phases that dominate the chalcophile and/or siderophile element budget of the silicate Earth. The macro- to micro-scale distribution of mantle sulphides and their trace chalcophile and siderophile elements, however, remains poorly understood. Herein we present new laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) spot and element mapping results for an assemblage of naturally occurring sulphide, alloy, and native metal minerals recovered from ophiolitic mantle peridotite and pyroxenite (Atlin, British Columbia). Sulphide (pentlandite, pyrrhotite, chalcopyrite), alloy (awaruite) and native metal (copper and iron) phases are interstitial to variably serpentinized olivine and pyroxene relicts at the micro-scale. Pentlandite (±pyrrhotite) occurs with magmatic clinopyroxene and is typically replaced by awaruite and native iron, suggesting super-reduced conditions during serpentinization and desulphidation of the low-temperature equilibrated mantle sulphide assemblage rather than the late addition of sulphide minerals during and/or after ophiolite emplacement. Element mapping results further suggest that gold, platinum and other metals were remobilized during serpentinization. New whole-rock nickel sulphide fire-assay (NiS-FA) platinum group element (PGE) results for the same Atlin ultramafic suite, however, yield flat chondrite-normalized profiles that scatter around the composition of the primitive mantle, suggesting that precious metal remobilization was limited to the micro-scale. Future work will focus on the paragenetic history of this ultramafic suite using a combination of whole-rock ultratrace geochemistry and isotopic studies.
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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 | 0.000 | 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) | 0.003 | 0.001 |
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".