Mantle Xenoliths from the Southeastern Slave Craton: Evidence for Chemical Zonation in a Thick, Cold Lithosphere
Bibliographic record
Abstract
We present the first data on the petrology of the mantle lithosphere of the Southeastern (SE) Slave craton, Canada. These are based on petrographic, mineralogical and geochemical studies of mantle xenoliths in Pipe 5034 of the Cambrian Gahcho Kué kimberlite cluster. Major types of mantle xenoliths include altered eclogite, coarse garnet or spinel peridotite, and deformed garnet peridotite. The peridotites belong to the low-temperature suite and formed at T=600–1300°C and P= 25–80 kbar in a thick (at least 220–250 km), cool lithosphere. The SE Slave mantle is cooler than the mantle of other Archaean cratons and that below other terranes of the Slave craton. The thick lithosphere and the relatively cool thermal regime provide favourable conditions for formation and preservation of diamonds beneath the SE Slave terrane. Similar to average Archaean mantle worldwide, the SE Slave peridotite is depleted in magmaphile major elements and contains olivine with forsterite content of 91–93·5. With respect to olivine composition and mode, all terranes of the Slave mantle show broadly similar compositions and are relatively orthopyroxene-poor compared with those of the Kaapvaal and Siberian cratons. The SE Slave spinel peridotite is poorer in Al, Ca and Fe, and richer in Mg than deeper garnet peridotite. The greater chemical depletion of the shallow upper mantle is typical of all terranes of the Slave craton and may be common for the subcontinental lithospheric peridotitic mantle in general. Peridotitic xenoliths of the SE Slave craton were impregnated by kimberlitic fluids that caused late-stage recrystallization of primary clinopyroxene, spinel, olivine and spinel-facies orthopyroxene, and formation of interstitial clinopyroxene. This kimberlite-related recrystallization depleted primary pyroxenes and spinel in Al. The kimberlitic fluid was oxidizing, Ti-, Fe- and K-rich, and Na-poor, and introduced serpentine, chlorite, phlogopite and spinel into peridotites at P < 35 kbar.
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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 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| 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".