Early diagenesis of inner-shelf phosphorite and iron-silicate minerals, Lower Cretaceous of the Orpheus graben, southeastern Canada: Implications for the origin of chlorite rims
Bibliographic record
Abstract
Abstract Wells in the Orpheus graben encountered the most proximal part of the deltaic Lower Cretaceous rocks of the Scotian Basin. More distal sandstones are important gas reservoir rocks, with good reservoir quality where Fe-rich chlorite (chamosite) rims on framework grains have inhibited quartz cementation. Cutting samples from the Orpheus graben show the presence of Fe-rich sheet silicates (berthierine or chamosite) and early diagenetic phosphorite. These minerals were analyzed by electron microprobe, and their textures were mapped with backscattered electron images. Studies in the North Sea have shown a relationship between high phosphorus and the presence of good chlorite rims in reservoir rocks. The mineralization of pore-water phosphorus, instead of its return to seawater, is favored by Fe-rich sediments and sorption on iron oxides during shallow sea-floor diagenesis. The Fe, Ti, and P contents are uncommonly high in Scotian Basin shales compared with global average shale compositions. The uncommon occurrence of inner-shelf phosphorite in this study is interpreted to be a consequence of the same high Fe content of the sediment that also favors the formation of Fe-rich sheet silicates. In rapidly deposited deltaic sandstones of the offshore reservoirs, the dominance of type 3 kerogen led to sulfate depletion occurring at depths of tens of meters and a corresponding great thickness for overlying Eh (oxidation potential)-controlled diagenetic zones. The thick Fe-reduction zone allowed the formation of early diagenetic berthierine, which on burial formed the chamosite rims that resulted in the improved reservoir quality in sandstones. The distribution of phosphorus minerals may be an indicator of conditions suitable for berthierine formation.
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 | 0.000 | 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) | 0.000 | 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 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".