Fluid inclusion evidence for subsurface phase separation and variable fluid mixing regimes beneath the deep‐sea PACMANUS hydrothermal field, Manus Basin back arc rift, Papua New Guinea
Bibliographic record
Abstract
Altered volcanic rocks were cored from over 350 m below the seafloor at the Papua New Guinea‐Australia‐Canada Manus Basin Hydrothermal Field (PACMANUS) deep‐sea hydrothermal field, in the eastern Manus back arc basin. Fluid inclusions in anhydrite veins reveal phase separation and fluid mixing beneath the seafloor. The anhydrite precipitated from high‐temperature fluids (150–385°C). At Roman Ruins, a site of active high‐temperature venting (220–276°C, measured by submersible), the fluid inclusion thermal depth profile is uniform and high temperature (242–368°C). At Snowcap, a site of warm water effusion (6–65°C), the fluid inclusions indicate high temperatures at depth (270–385°C) but both low and high temperatures in the shallower section. This indicates a flow regime dominated by vertical advection and shallow entrainment and mixing with cool seawater. Inclusions at Snowcap exhibit extreme salinity variations due to phase separation at temperatures above 350°C. Fluids contain Na, Cl, Fe, Zn, Mg, and Ba and a minor gas component such as CO 2 or CH 4 . Most inclusions at Roman Ruins exhibit salinities that fall within the range of those observed at modern active vent sites along the mid‐ocean ridge system. Fluid inclusion temperatures support a hypothesis, developed previously from Sr‐isotopic analysis, that the subseafloor at Snowcap is characterized by mixing between deep‐sourced hot hydrothermal fluids and cold seawater‐like fluid. Both heating of seawater and cooling of upwelling hydrothermal fluids can be recognized by combining isotopic and fluid inclusion data. In contrast to Snowcap, the regime at Roman Ruins is less varied, with uniformly high‐temperature upwelling fluids that have hydrothermally dominated Sr‐isotopic ratios.
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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 | 0.000 |
| 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 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".