Kaolinite and Gibbsite Weathering of Biotite within Saprolites and Soils of Central Virginia
Bibliographic record
Abstract
The mineralogical and chemical characteristics of saprolites and soils developed from granulitic, monzonitic, and charnockitic gneisses and mylonites of the Blue Ridge Mountains and western Piedmont foothills of central Virginia, were studied. Micromorphological, x‐ray diffraction (XRD), scanning electron microscopy (SEM), and microprobe analysis showed that the mineralogical and geochemical evolution of biotite in profiles developed on gneisses is consistent with pseudomorphic weathering of mica to kaolinite and halloysite, with or without a mica–vermiculite intermediate phase. On mylonitic rocks, saprolites and soils also contain multimineral pseudomorphs after biotite, in which gibbsite crystals eventually fill the whole volume. There is evidence of topotaxial formation of halloysite after biotite. Although gibbsite is present at the first stages of the weathering of biotite, it is not clear if gibbsite forms directly from the mica or if it is a weathering product of kaolinite and/or halloysite. The source of aluminium may also be located outside the original biotite crystal. These multimineral assemblages suggest that microenvironments of weathering are controlling the formation of secondary products from the parent biotite rather than the so called anti‐gibbsite effect , at least at this scale of investigation. It is suggested that the mylonitic fabric and subvertical foliation planes of these rocks are responsible for this mineralogical and geochemical evolution.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".