Spatial and temporal variability in the geochemistry of the sediments at the Main Endeavour Field, Juan de Fuca Ridge
Bibliographic record
Abstract
Sediments near hydrothermal vents are enriched in metals derived directly from hydrothermal fluids (e.g., Fe, Cu, Zn, Mn) and those associated with scavenging and co-precipitation from seawater with hydrothermally derived Fe-sulfides and Fe-oxyhydroxide minerals (e.g., P, V, Co, Mo, As, REEs). The sediments surrounding active venting have high concentrations of these elements which decrease with distance from the vents due to both hydrothermal plume dilution with seawater and sedimentation of hydrothermal particles. The composition of hydrothermal sediments from the Main Endeavour Field on the Juan de Fuca Ridge, approximately 300 km off the coast of Vancouver Island, was determined using samples collected in sediment traps at three locations along a transect below the hydrothermal plume. These traps were deployed on-axis, 3 km, and 9 km off-axis allowing the spatial variability of the hydrothermal component of the sediments to be assessed. The chemical composition and mass accumulation rates of the hydrothermal component is governed by particle formation in the near vent region and is controlled by particle settling rates with distance from active venting. The concentration and mass accumulation rate of the hydrothermal component of the sediment decreases rapidly with distance, with an order of magnitude decrease between the on-axis and 3 km off axis sediment trap samples, and a further 1-2 orders of magnitude decrease from 3 km off axis to 9 km off axis. Sediment trap samples are also used to create a high-resolution time series of hydrothermal sedimentation over the course of the approximately year sampling period, with each on-axis sample collecting 21 days of sediment and each off-axis sample collecting 12 days of sediment. These samples allowed for an initial assessment of the temporal variation in the chemical composition and mass accumulation rate of the hydrothermal sediment. The variability observed in the hydrothermal component mass accumulation rate suggests that physical oceanographic processes (e.g., flow reversal) impacts the rate of sedimentation. The base of a 50 cm sediment core, collected 2.6 km northwest of the Main Endeavour Field, was dated at ~6,000 years and a high-resolution geochemical reconstruction is used to determine how the hydrothermal component has changed on a 100–1000 year time scale. The comparison of the sediment core to fresh sediment collected by the sediment traps is used to understand how post-depositional changes affect the composition of the hydrothermal component preserved in sediment, as well as the utility of some elements, such as Mn, in reconstructing paleo-hydrothermal sedimentation.
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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 | 0.000 | 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) | 0.000 | 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".