Transient convective circulation in a sedimented ridge setting: Implications for applying geochemical data to estimate permeability
Bibliographic record
Abstract
For an open, sedimented ridge setting we investigate by means of transient numerical simulations hydrologic factors that can influence chemical signatures of mineral alteration, and how these features relate to the permeability of the upper oceanic crust. The transient state we consider involves three stages: (1) starting from a static flow field and a conductive thermal regime, flow in basement rocks is initiated as unstable convection; (2) with the inflow of seawater to the basement, the convection pattern evolves into a stable convection cell linking the recharge and discharge sites on the seafloor; and (3) convection weakens through time as the system offsets the initial thermal condition to attain a steady state. The duration of each stage, and the extent of the region in the basement undergoing fluid exchange with seawater varies with permeability. By the end of stage 2, for basement permeabilities between 1 × 10−14 and 1 × 10−13 m2, most of the basement and the deeper sediments surrounding the discharge zone is hydrologically isolated, but with active recirculation inside this zone. Through‐flow of seawater is restricted to a relatively narrow boundary layer. The unstable flow geometry during stages one and two is reflected in fluctuations of recharge and discharge rates into and out of the basement, and periodic variations in temperature of the discharging fluids. Fluid discharge at steady state is approximately one‐half of the average occurring during stage one. Changing flow patterns through time lead to a strongly heterogeneous evolution of water/rock ratios in the basement. Average water/rock ratios for the basement approach a log‐log linear correlation with basement permeability as steady state is reached.
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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 | 0.006 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 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".