Fluid segregation and retention in deep‑seated rocks near percolation thresholds
Bibliographic record
Abstract
Fluid segregation in deep-seated rocks has profound implications for their physical and chemical properties. Gravity drives the segregation of fluids interconnected through grain edges and corners, along with the compaction of the rock matrix, whereas isolated fluids are retained in the rocks. For wetting fluids, the critical volume fraction (i.e., percolation threshold) separating these two cases is principally determined by the balance and anisotropy of solid-fluid interfacial tensions (i.e., dihedral angle and faceting effect); however, the processes controlling the percolation threshold for non-wetting fluids are unclear, despite their critical importance, especially in the amount of pore fluids down-dragged in subducting slabs to the Earth’s interior. Hence, we implemented a combined approach involving high-pressure rock synthesis, high-resolution synchrotron radiation X-ray computed microtomography (CT) imaging, and numerical permeability computation to better understand how the permeability decreases and fluids are retained at low fluid fractions. We chose quartzite as a well-studied natural rock analog that is simplified but does not lose its essence as a silicate polycrystalline aggregate. A mixture of finely ground quartz and amorphous silica powders was sealed in Pt-lined Ni capsules with C-O-H fluid sources at different fractions and compositions and hot-pressed using a piston-cylinder apparatus. The dihedral angles of the experimental systems were 52° and 61–71° for the wetting and non-wetting systems, respectively.In the wetting system, fluid connectivity rapidly decreased to approximately zero when the total fluid fraction decreased to 3.0–3.7 vol. %, mainly due to the grain faceting effect, consistent with the results of the previous study. In the non-wetting systems bearing CO2-rich fluids, the cutoff of fluid tubules isolated 4.8–6.2 vol. % of the fluid. A streamline computation based on the X-ray CT images of the experimental products revealed that the fluid flow just above this threshold focused on a few channels, establishing efficient channelized fluid pathways. These retained fluid fractions are higher than those in the previous assessment based solely on the dihedral angle, that is, the pinch-off condition for ideal (isotropic and homogeneous) fluid geometry and the equilibrium fluid fraction that minimizes the total interfacial energy of the fluid-rock system. Hence, the amount of aqueous fluids dragged down to the Earth’s interior could be higher than previously estimated, although the specific volume fraction depends on the anisotropy and heterogeneity of the system of interest.
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 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 | 0.000 | 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 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".