Experimental evidence for light Ba isotopes favouring aqueous fluids over silicate melts
Bibliographic record
Abstract
Barium (Ba) is a fluid mobile element and enriched in the Earth's crust, which has potential implications for constraining fluid activities during magmatichydrothermal processes. However, the behaviour of Ba and its isotopes during fluid exsolution from magma is poorly known. Here we present an experimental study on determining the Ba partition coefficient (D FLUID-MELT ) and equilibrium isotope fractionation factor ( 138/134 Ba FLUID-MELT ) between aqueous fluids and silicate melts with different chemical compositions at 700-900 C and 200 MPa using cold seal pressure vessels. The results show that D FLUID-MELT ranges from 0.02 to 0.20, while 138/134 Ba FLUID-MELT [1000 ( -1)] ranges from -0.62 to -0.14 . Both D FLUID-MELT and 138/134 Ba FLUID-MELT positively correlate with temperature, the salinity of fluid and alumina saturation index (ASI) of melt. The finding that light Ba isotopes are enriched in aqueous fluids relative to silicate melts suggests that the fluid exsolution process cannot explain the observed light Ba isotopic compositions of some granites. Moreover, the experimentally determined 138/134 Ba FLUID-MELT is useful for tracing fluid activities in felsic intrusion-related hydrothermal deposits and in seafloor hydrothermal 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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".