Bibliographic record
Abstract
A ca. 1.85 Ga paleosol developed on seafloor-altered mafic rocks is preserved beneath continental sandstones and conglomerates of the Missi Group near Flin Flon, Manitoba. Previous work has focused on a locality where the paleosol is developed on pillowed greenstone (chlorite + albite + epidote + calcite + quartz + Fe–Ti oxides ± mica). This area has been revisited and a new (∼5 m) profile was excavated and sampled at a very high density for geochemical (major element; ∼60 samples) and mineralogical (petrography, X-ray diffraction) investigation. The high sampling density has revealed a relatively sharp immobile-element offset (e.g., Al/Ti) in the profile. This could reflect weathering across two separate parent rocks or preferential addition of allochthonous material into the top of the profile. Regardless, comparison with a wide suite of volcanic rocks in the stratigraphy suggests that the original concentration of Fe and probably also Ca and Mg in the greenstone on either side of the boundary was similar, permitting quantitative treatment of major-element trends. The profile shows pronounced upward loss of Ca, Mg, Mn 2+ , and Fe 2+ and a corresponding increase in Al, Ti, and total Fe. Physical weathering features, such as corestones, are well preserved and show progressive alteration upwards in the profile in parallel with the chemical trends. Deep in the profile, Na and Ca are lower than the greenstone due to the weathering of albite and epidote, whereas Mg, Fe, and Mn were largely retained in chlorite and secondary dolomite. Upwards in the profile, the loss of chlorite and dolomite and the increase of illite – mixed-layer clays and white mica (probably 2:1 layer or mixed-layer clays originally) and hematite are accompanied by a transition from green to maroon colour. Above a well-defined depth in the profile, carbonate is virtually absent, and the paleosol is highly depleted in Ca. This transition in the paleosol coincides with the immobile-element offset. The significance of this coincidence remains to be explored. Reworking of regolith (e.g., rip-up clasts) occurred during deposition of the Missi sediments, and burial and subsequent metamorphism resulted in the upward enrichment of K and Na and the associated conversion of pedogenic clays to illite and micas (muscovite and paragonite). Crosscutting quartz and epidote veins and tourmaline formation near the unconformity contact implies minor post-burial fluid movement. Despite these complexities, there is consistent retention of Fe through formation of pedogenic Fe oxides, attested by the near-constant ∑Fe/Al ratio in the profile. There is very little evidence for subsequent Fe reduction by hydrothermal or organic fluids. Instead, trends in the Fe speciation are controlled predominantly by the modal variation of Fe–Ti oxides in the greenstone and spheroidal weathering textures in the paleosol.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 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) | 0.008 | 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 teacher head, 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".