Regional Diagenesis and Fluid Flow Study of the Early Triassic Montney Formation as Related to H2S Generation
Bibliographic record
Abstract
The regional diagenetic evolution of the Early Triassic Montney Formation was investigated using detailed petrographic techniques (optical and SEM/EDXS/CL) and multiple bulk and in-situ isotope geochemical data to address the nature of diagenetic fluids, water/rock interaction, and geological, geochemical, and structural processes controlled the formation of sulfates (anhydrite and barite), sulfides (H2S and pyrite), and carbonates (calcite and dolomite). According to the results of this study, the Montney Formation contains both early and late diagenetic anhydrite and late barite cement mainly formed by the Montney Formation pore water and incursion of structurally-controlled Devonian-sourced hydrothermal sulfate-rich fluids. Three pyrite forms, i.e., framboidal, recrystallized, and coalesced with distinct δ34S values, were identified. The sulfur isotope composition of anhydrite/barite, H2S, and pyrite demonstrates both microbial and thermochemical sulfate reduction (MSR and TSR) controlled the diagenetic sulfur cycle of the Montney Formation. The present-day produced-gas H2S was dominantly originated from the in-situ thermochemical sulfate reduction process and partially migrated from underlying formations. The Montney Formation is also comprised of three and four generations of early to late calcite (C1-C3) and dolomite (D1-D4) cement, respectively. Bulk δ13C and δ18O values, and 87Sr/86Sr isotope ratios of carbonate cement suggest water/rock interaction between hot basinal brines, Precambrian metasediments, and siliciclastics in the basin. Moreover, hydrothermal fluids as well as burial diagenesis appear to have contributed to the formation of carbonate cement. The overall diagenetic evolution of the Montney Formation was controlled by intraformational (Montney Formation pore water), and cross-formational fluid flow driven by hydrothermal activities and tectonic evolution of the Canadian Cordillera.
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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 | 0.000 | 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".