Preservation of Hydrothermal Fluid Copper Isotope Signatures in Chalcopyrite‐Rich Chimneys: A Case Study From the PACMANUS Vent Field, Manus Basin
Bibliographic record
Abstract
Abstract Copper isotopes (δ65Cu) in hydrothermal fluids have the potential to provide information on ore‐forming processes occurring below the seafloor, but Cu isotope data from high‐temperature fluids are scarce. Here, we examine the extent to which coexisting sulfide minerals in a hydrothermal chimney can preserve fluid Cu isotope ratios using a fluid‐solid pair of a black smoker (333°C) from the Roman Ruins vent area (PACMANUS) in the Manus Basin. Two ca. 3 cm long transects through the chalcopyrite‐rich chimney wall show an increase in δ65Cu from 0.48 to 2.28‰ from the interior to the exterior, coupled with limited variation in sulfide δ34S (1.52–4.72‰). The Cu isotopic composition of chalcopyrite from the innermost wall closely resembles the δ65Cu value of the paired hydrothermal fluid, indicating that chalcopyrite in the inner ∼5 mm of the chimney records the Cu isotope ratio of the venting fluid. Beyond this, an increase in sulfide δ65Cu toward the exterior correlates with an increase in the relative abundance of secondary Cu sulfides. The appearance of bornite coincides with the presence of small barite crystals, suggesting this represents a redox gradient between reduced hydrothermal fluids and oxidized seawater admixing inwards. Elevated δ65Cu in this zone can be explained by the precipitation of secondary Cu sulfides from 65Cu‐enriched fluids formed during oxidative chalcopyrite dissolution. Our findings indicate that interactions with oxidizing seawater shift chalcopyrite δ65Cu values over small spatial scales, and that caution must be applied if chimney sulfides are used to reconstruct δ65Cu values of high‐temperature hydrothermal fluids.
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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 | 0.001 |
| 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".