Alkaline hydrothermalism in S-, rare metal and P-rich black shales
Bibliographic record
Abstract
Alkaline hydrothermal fluids favor phosphate chemistry and the dissolution of organic acids and bases, and were proposed as a possible scenario for the emergence of life in the Archaean (Russell & Hall, 2002). In high S2 environments, Fe-sulfide membranes would have thus played a major role. Most of the studies on microfossils in Archaean chert plead however for acidic fluids. Furthermore the record of sulfurized microfossils in S-rich cherts is poorly known (Rasmussen, 2000). To improve the experiential knowledge in this field, we studied Upper Devonian black shales from a continental margin (Selwyn Basin, Canada) for micromineralogy and mineral chemistry (SEM-EDX-EMPPIXE-NR). The sediments have been pervaded by alkaline fluids (< 260°) that precipitated successively Na-, Kand BaK-feldspar, quartz, Caand REE-phosphates, U-Ti-oxides and Ag-Cd (Cl) alloys. Tube worms (about 30μm) as known from hydrothermal vents, are preserved as Fe-(Ni)-sulfides. Biogenic silica bands are separated by nanometric Znsulfides, probably derived form microbial reduction. Sulfurized worm tubes host several hundreds to thousands ppm of Se, Mo, As, Sb, Tl. Diagenetic abiogenic sulfides are Ni and Se rich. Nitrogen was analysed in biogenic and abiogenic sulfides (about 400 ppm), phosphatic fossil fragments (800 ppm), organic matter (OM, 6000 ppm), quartz (800 ppm). Highest contents occur in hydrothermal feldspars (1-2 wt.%). A two-step N release is proposed for the present N-repartition: (1) OM breakdown provides nutrients for the tube worms. (2) Biomineralisation of the fauna partly releases N to the diagenetic fluids and is incorporated in abiogenic sulfides and quartz. Ammonium (NH4 ) derived from the breakdown of organic matter is fixed in feldspars (at high T), where it replaces K in the silica structure.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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) | 0.021 | 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 teacher head, 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".