Growth history of a diffusely venting sulfide structure from the Juan de Fuca Ridge: A petrological and geochemical study
Bibliographic record
Abstract
Centimeter‐scale mineralogical and chemical analyses of a diffusely venting, ∼280°C sulfide structure (called Roane) from the Mothra Hydrothermal Field on the Juan de Fuca Ridge reveal a complex growth history. These analyses document four well‐defined zones, which from the exterior to the interior of the structure include a barite‐silica zone (Fossil Worm Tube Zone), a silica‐sulfide zone (Silica Zone), a sulfide‐silica zone (Outer Sulfide Zone), and a sulfide ± gordaite ± silica zone (Inner Sulfide Zone). These features are a product of a myriad of processes that include extensive mineral replacement, ingress of seawater, fracturing and breakout of hot hydrothermal fluids, significant conductive cooling, and the sustained, broad‐scale outflow of warm fluids from the walls through a porous and permeable matrix. Roane lacks an open, throughgoing, chalcopyrite‐lined, central conduit. Instead, it hosts an anastomosing, discontinuous network of tortuous channels within the interior of a sponge‐like matrix of amorphous silica, sulfide, sulfate, and clay minerals. Megafaunal communities at the summit and sides of this mature, diffusely venting chimney provide a constructional framework for new growth. Isolation of hydrothermal fluid from seawater during progressive fossilization of megafauna and the early formation of barite‐silica assemblages promote flow of higher‐temperature fluids within the interior. Continued isolation of interior higher‐temperature fluids, through increased mineral precipitation and expansion of the structure, leads to a Zn sulfide + pyrite‐dominated permeable matrix and a network of tortuous channels that form a central porous conduit. This conduit is shielded by a weakly silicified, metal sulfide inner wall and a strongly silicified outer wall. The most outer portions of the walls are highly porous and sites of significant advection and mixing between hydrothermal fluids and seawater. The mineralogy and chemistry of Roane are strongly affected by ammonia‐ammonium buffering of the pH during cooling of the hydrothermal fluids. The two major results of the buffering are (1) precipitation of Zn sulfide at higher temperatures than are typical for bare‐rock systems, leading to the correlation of Cu, Zn, Cd, and Se and (2) increased deposition of amorphous silica and clay minerals.
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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 | 0.001 | 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".