Tungsten Isotope Composition of Archean Crustal Reservoirs and Implications for Terrestrial μ<sup>182</sup>W Evolution
Bibliographic record
Abstract
Abstract The evolution of Earth's major geochemical reservoirs over ~4.5 × 10 9 years remains a matter of intense study. Geochemical tools in the form of short‐lived radionuclide isotope ratios ( 142 Nd/ 144 Nd and 182 W/ 184 W) have expanded our understanding of the geochemical variability in both the modern and ancient Earth. Here, we present 142 Nd/ 144 Nd and 182 W/ 184 W data from a suite of rocks from the Slave craton that formed over a 1.1 × 10 9 year time span in the Archean. The rocks have consistently high 182 W/ 184 W, yet 142 Nd/ 144 Nd that is lower than bulk mantle and increased over time. The declining variability in 142 Nd/ 144 Nd with time likely reflects the homogenization of compositional heterogeneities in the silicate Earth that were initially created by differentiation events that occurred prior to 4.2 Ga. The elevated 182 W/ 184 W recorded in the Slave samples help refine models for the broader W‐isotope evolution of the silicate Earth. Globally, the Archean mantle that formed continental crust was dominated by 182 W/ 184 W elevated by some 10–15 ppm compared to the value for the modern upper mantle. The Slave craton lacks significant volumes of komatiite yet has elevated 182 W/ 184 W until 2.9 Ga. This observation, combined with the presence of other komatiite suites that have low 182 W/ 184 W, suggests that deep‐seated sources contributed low 182 W/ 184 W in the Archean Earth. The regional variability in 182 W/ 184 W may be explained by invoking chemical and/or isotopic exchange between a well‐mixed silicate Earth and the core or a portion of the lower mantle whose W‐isotope composition has been influenced by interaction with the core.
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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 | 0.000 |
| 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) | 0.000 | 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 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".