GEOMETRY OF ISOGRADIC, ISOTHERMAL, AND ISOBARIC SURFACES: INTERPRETATION AND APPLICATION
Bibliographic record
Abstract
An isograd represents a line on a map resulting from the intersection of an isogradic surface with the topography. It is inferred to represent a metamorphic reaction and is inherently diachronous because of the time required to move heat, fluid, and reactions through the rocks. Relief of 500 m or more or reconstruction of post-metamorphic faulting and folding will be essential to estimate the orientation of an isogradic surface. Ductile rocks require that isobaric surfaces dip gently during metamorphism, and they must do so in restored sections. Isotherms can be constructed into cross-sections because the angle between the isograds and isotherms are a function of the P–T slope of univariant reaction curves. Near Mica Creek, British Columbia, we can infer an 1100-bar difference in pressure along a kyanite–sillimanite (ky–sil) isograd, based upon structural relief. The experimentally determined ky–sil P–T curve suggests a P/T slope of ~20 bars/°C. We calculate the apparent variation in P and T along the isograd and reconstruct the isotherm geometry. Dehydration-reaction curves, at relatively high P, have steep P–T slopes, and the associated isogradic surfaces can approximate isothermal surfaces. Some dehydration isograds are “smeared out”, but for regional scales, these latter isogradic surfaces at high P still approximate the isothermal surface geometry. Data on isogradic surfaces can be used to set limits on parts of the P–T grids for pelitic rocks. Locally, bathozone-defining isobaric surfaces can be reconstructed; we suggest a ΔP of 2 kbar for the garnet – biotite – kyanite bathozone.
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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 | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.004 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.004 | 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".