Chlorine stable isotope ratios as tracer for pore‐water advection rates in a submarine gas‐hydrate field: implication for hydrate concentration
Why this work is in the frame
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Bibliographic record
Abstract
Abstract At Ocean Drilling Program Site 997 in Blake Ridge gas‐hydrate field in West Atlantic, pore‐water studies revealed a pronounced downward depletion of the heavy chlorine isotope to nearly −4‰ δ 37 Cl at approximately 750 m below sea floor (mbsf) associated with a 10% downward chlorinity decrease. This is one of the stronger 37 Cl depletions hitherto reported for marine pore waters. Chlorinity reductions in hydrate‐bearing sediments commonly result from fresh‐water release by hydrate melting. However, in situ measurements at Site 997 suggest that >50% of the chlorinity reduction occurred prior to hydrate dissociation. Modeling the chlorinity profile shows that advection of a strongly 37 Cl‐depleted, low‐chlorinity water (506 m m ) from below the drilled sequence can explain the reduction prior to sampling. Fitting the model to the δ 37 Cl curve yielded an advection rate of 0.18 mm year −1 . Diffusive mixing with near‐0‰‐ δ 37 Cl paleo‐seawater with maximum chlorinity at shallow subsurface depths (561 m m at approximately 20 mbsf) produced the smooth, steady trend. Separating that part of the freshening caused by advection and diffusion from that due to hydrate dissociation allowed estimation of average hydrate concentrations of 3.8% of the pore space (up to 24.5% in hydrate‐rich layers; near‐100% in rare massive hydrate layers). The deep‐seated source of the 37 Cl‐depleted, low‐chlorinity water remains unknown and might be located below the sedimentary section in the oceanic basement.
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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 | 0.000 | 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) | 0.001 | 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 it