ORDER AND CHAOS IN THE OLIVINE UNDERWORLD: TWO MECHANISMS FOR THE FORMATION OF BASAL OLIVINE LAYERS
Bibliographic record
Abstract
Recent debate has questioned the efficiency of magma differentiation in basaltic magma chambers (Marsh, 2013). As a result, petrologists are increasingly inclined to interpret olivine cumulate layers in small intrusive bodies as separately injected slurries, as opposed to the result of in-situ differentiation. Two sills with basal olivine layers, the 0601 sill, Victoria Island, NWT, Canada, and the Palisades Sill, Fort Lee, NJ have been examined in detail. First, it can be shown that the 0601 sill could have formed by the emplacement of a single phenocryst bearing magma, followed by settling of the initial phenocryst load, and in-situ differentiation. Second, a high-resolution analysis of the internal ordering of the Palisades Sill olivine horizon, widely recognized as the result of an olivine slurry, is described in order to create a generalizable model of basal olivine layers formed via slurry emplacement (Husch, 1990; Gorring, 1995). Both sills were analyzed for whole rock major and trace element compositions, mineral compositions, crystal size distributions and modal mineralogy. Parent-Daughter modeling, Pearce Element Ratio Analysis, trace element modeling, and MELTS (Ghiorso and Sack, 1995; Asimow and Ghiorso, 1998) were then used to model formation mechanisms. Finally, the 0601 sill olivine cumulate layer is com-pared with the Palisades Sill olivine horizon. While both olivine cumulate zones look superficially similar, detailed investigation reveals that a well developed trend of progressively increasing olivine upward from the base, as observed in the 0601 sill is best explained by crystal settling within an initial phenocryst-phyric magma, followed by in-situ differentiation, and cannot be explained by a slurry emplacement process.
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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 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".