Water-rock Interactions in Geologically Diverse Regional Aquifers of Northeastern Ontario
Bibliographic record
Abstract
Information regarding the characterization and controls of groundwater chemistry in Precambrian silicate aquifers of northeastern Ontario is limited. This study utilizes the analysis of halogens, major ions, select trace ions, δ18OH2O, δ2HH2O, δ34SSO4, δ18OSO4 and tritium of 271 groundwater samples collected from Precambrian bedrock aquifers to present a characterization of groundwater chemistry for northeastern Ontario, in addition to 55 groundwater samples collected from Paleozoic aquifers of Manitoulin Island in Lake Huron. The analysis of 87Sr/86Sr on 98 of the total groundwater samples collected are also presented here. Aquifers are hosted in a variety of rock types including Archean rock of the Superior Province to the north of the study area, Paleoproterozoic Huronian Supergroup rocks in the west, metamorphosed Precambrian rock of the Grenville Province in the southeast, and Paleozoic carbonate rocks on Manitoulin Island. Water-types, Cl- versus Cl/Br bivariate plots, and other geochemical and isotopic methods were employed to discern sources of salinity and to identify zones of anomalous groundwater chemistry. The sources of salinity were identified as mixing with trace amounts of deep brines, water-rock interaction, and influence by surface contaminants, including road salt. A zone of anomalous chemistry forms a northeast-southwest linear trend within the Grenville Province running parallel to the Grenville Front. This zone is characterized by reducing conditions (as low as -130.8 mV), elevated TDS (up to 1250.7 mg/L), Br- (up to 3.44 mg/L), Cl- (up to 386.08 mg/L), I- (up to 192 µg/L), B (up to 2249.7 µg/L), and depleted Sr isotope values (as low as 0.708667). A group of samples characterized by Na-Cl geochemical facies, unconfined aquifer conditions, and parameters reflective of surface influence (oxidizing conditions, low pH, elevated TDS (up to 1304.4 mg/L) are commonly spatially associated with major highways. A zone of groundwater with a Na-K-HCO3 geochemical facies coincides with thick overlying Quaternary units of glaciolacustrine material deposited along the north shore of Lake Nipissing. The presence of a confining layer over this area reduces surface influence and allows for longer residence times leading to alkaline and reducing conditions and increased F- concentrations as a result of ion exchange. Groundwater along the north shore of Manitoulin Island with higher TDS (up to 7664.3 mg/L), Br- (up to 8.0 mg/L), Cl¬- (up to 4357.55 mg/L), I¬- (up to 134.0 µg/L), and B (up to 10475.0 µg/L) concentrations relative to the south shore of the island is likely related to the presence of shale and reducing conditions in the Georgian Bay and Blue Mountain formations. These results provide a general characterization of groundwater geochemistry in a geologically diverse region in northeastern Ontario and improved understanding of the controls of groundwater chemistry in silicate Precambrian aquifers.
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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 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".