Aligned hydrothermal fluid‐flow pathways in Middle Permian near‐shore marine sediments beneath a basaltic lava flow
Bibliographic record
Abstract
ABSTRACT Tubular and curviplanar structures, outlined by the occurrence of haematite/goethite, chlorite, quartz and albite, are developed in the Middle Permian Broughton Formation in the southern Sydney Basin, New South Wales, Australia. These structures are interpreted as fluid‐flow pathways resulting from the ejection of heated pore fluids as a thick (>30 m) basaltic lava (the Bumbo Latite Member) was emplaced rapidly on top of near‐shore, unconsolidated, wet, sandy marine sediments (the 53 m thick Kiama Sandstone Member). Evidence of fluid‐flow pathways in the sandstone is observed for ~20 m below the basalt. Subhorizontal and parallel, elongate tube‐like flow structures tend to be between 5 cm and 30 cm in diameter and are exposed laterally for a few tens of metres on the shore platform, although their full extent cannot be determined. Fluid‐flow pathways are marked by intense mineralisation and include enclosed tubes as well as unenclosed sheets, which may be flat or locally highly curved. Cross‐cutting relationships reveal several generations of the tube‐like features and imply the passage of hydrothermal fluids through the tubes. However, while significant alteration is apparent in the tube rims, little or no alteration is visible inside tubes at the hand specimen scale, but on a microscopic scale, the tube cores show alteration and extensive development of laumontite. Fluid‐flow features are grouped in moderately to well‐sorted sand beds and are underlain by layers with a higher silt component and exhibiting extensive bioturbation. These features imply that bedding‐controlled sediment porosity and permeability played a large role in determining the location of fluid‐flow conduits. The hot lava heated and pressurised the pore water, inducing horizontal hydrothermal fluid flow away from the lava and producing the mineral assemblage defining the fluid‐flow pathways.
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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 | 0.001 | 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".