Geochemical controls on coupled glauconite–feldspar diagenesis and its implications for fluid–rock interactions in glauconitic-rich sandstones
Bibliographic record
Abstract
Glauconite and K-feldspar, two abundant aluminosilicate minerals in natural glauconitic sandstones, undergo complex diagenetic dissolution in deep subsurface environments, influencing fluid chemistry and mineral reactivity. Their coupled dissolution forms a dynamic feedback system that influences fluid storage capacity and flow pathways in glauconitic sandstones, yet the mechanisms governing their interaction remain insufficiently understood. This study revisits the diagenetic processes controlling their coupled dissolution and its impact on secondary porosity evolution in deeply buried glauconitic sandstones of the Oligocene Songnan-Baodao Sag, Qiongdongnan Basin. By integrating petrography, geochemical modelling, and microstructural analysis of glauconite-feldspar interactions in varying partial pressure of CO 2 (pCO 2 ) and mineralogical conditions, we systematically investigate the dissolution characteristics and controlling factors of the coupled dissolution process. Geochemical modelling demonstrates that microfracture development in glauconite markedly increases its effective surface area, accelerating dissolution and enhancing accumulation of , , and in pore waters, which in turn modulates K-feldspar dissolution and precipitation dynamics. The pCO 2 critically controls mineral solubility with high pCO 2 sustaining continuous K-feldspar dissolution, whereas low pCO 2 leads to rapid solution saturation, suppressing further dissolution and potentially inducing re-precipitation that may occlude porosity. Furthermore, the glauconite-to-K-feldspar mass ratio governs their coupled behaviour, low glauconite content promotes feldspar dissolution, while high glauconite abundance inhibits it. This relationship is reflected in two distinct patterns of porosity development, one characterized by dominant glauconite dissolution with limited alteration of K-feldspar, and another where K-feldspar dissolution is more pronounced while glauconite remains relatively unaltered. These findings clarify key controls on glauconite-feldspar diagenesis and provide theoretical insight for predicting porosity evolution in deeply buried glauconitic sandstone reservoirs. They also highlight the broader implications for CO 2 storage and geothermal energy systems, where mineralogical variability exerts a strong influence on fluid-rock interactions in sedimentary basins.
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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 | 0.001 |
| 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) | 0.001 | 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 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".