Constraints on Oxygen Fugacity during Sulfide Segregation inthe Voisey's Bay Intrusion, Labrador, Canada
Bibliographic record
Abstract
Measurements of the Fe and Ni content of olivine and coexisting bulk sulfide from the different sulfide segregations within the Voisey’s Bay intrusion reveal systematic variations in Fe-Ni partitioning with sulfide nickel content. In light of the recent experimental results of Brenan and Caciagli (2000), such variation is interpreted as arising from differences in f O2 between the different sulfide bodies. Assuming that each sulfide body became closed to Fe-Ni exchange at the same temperature, the observed f O2 variation is interpreted to reflect intrinsic differences in their oxidation state. Varied-textured troctolite from the Eastern Deeps records the highest oxygen fugacities (10 –10.4 ), with progressively lower f O2 documented in samples from the basal breccia sequence of the Eastern Deeps (10 –11.1 ), Discovery Hill (10 –12.0 ), and Reid Brook zones (10 –12.4 ). In light of both isotopic and petrographic evidence for open-system behavior within the Voisey’s Bay magmatic system, a model of magma reduction involving assimilation of carbon-bearing country rock (i.e., the Tasiuyak gneiss) has been explored. Calculations suggest that the assimilation of graphite (which is present in the more reduced Voisey’s Bay samples) by a relatively oxidized parental magma at high temperature, then closure at lower temperature, can account for both the absolute values and variation in f O2 within the Voisey’s Bay sulfide bodies. Consideration of the f O2 exhibited by other olivine- + sulfide-saturated intrusive suites reveals a range from relatively oxidized, as typified by most oceanic basalts, to the relatively reduced native iron-bearing dike from Disko Island (Greenland). As in the case for Voisey’s Bay, intrusive and extrusive samples that yielded relatively low f O2 also show clear evidence for assimilation of a reducing agent.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.003 | 0.001 |
| Scholarly communication | 0.002 | 0.000 |
| Open science | 0.001 | 0.001 |
| 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".