The impact of CO2-charged fluids on the aqueous geochemistry of terrestrial aquifers
Bibliographic record
Abstract
Understanding the formation and evolution of subsurface CO 2 -rich terrestrial fluids and reservoirs is key for modelling the storage of CO 2 in the crust, fracture-controlled fluid flow, and/or diffusive transport of fluids from deep crustal settings. However, migration and exchange mechanisms associated with CO 2 -rich environments remain poorly constrained. In at least one natural CO 2 -rich setting, a Precambrian crystalline brine component has been postulated based on δ 18 O and δ 2 H signatures which plot above the Global Meteoric Water Line. In this study we evaluate the intriguing potential role of migration and mixing of deep fluids in the shallow subsurface using a novel geochemical and microbiological framework approach which incorporates noble gas, stable isotope, and microbial diversity-based approaches. Through targeting a series of 10 springs which sample depths of up to 250 m at Saratoga Springs, NY, USA, this integrated approach finds no evidence of a deep shield brine component and reveals only migration of a principally deep crustally-derived CO 2 (87.2–99.3 %) with a minor mantle component. Instead, this study reveals how putative CO 2 dissolution-enhanced water–rock interaction coupled with ≤17 % CO 2 -H 2 O 18 O isotopic exchange can produce the observed aqueous geochemical composition, including the apparent shield brine signal. Microbial community data presented here also suggest distinct assemblages between shallow, freshwater and deep, saline spring fluids in line with geochemical interpretations. Crucially, our novel integrated approach highlights how migrating CO 2 -rich phases in subsurface environments can overprint and drive geochemical reactions in the subsurface to produce aqueous geochemistries which mimic characteristics of unrelated deep fluid systems.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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 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".