Weak B‐Type Olivine Fabric Induced by Fast Compaction of Crystal Mush in a Crustal Magma Reservoir
Bibliographic record
Abstract
Abstract Understanding the deformation mechanisms of olivine has been considered as the crucial factor in tracing the dynamic processes from seismic anisotropy. Due to extensive overprinting of deformation and alteration, natural examples of original magmatic fabric of olivine are scarce. In this study we selected one wehrlite and three dunite samples from a deep borehole in the Poyi mafic‐ultramafic intrusion in the Tarim Craton. The fresh samples show adcumulate texture and plastic deformation of dry olivine (≤10 ppm H 2 O). Thermobarometer calculations yield crystallization conditions at 200–400 MPa and >1,124–1,275 °C. Olivine developed a B‐type fabric characterized by a concentration of [001] axes parallel to the interpreted lineation and that of [010] axes normal to the interpreted foliation. Activation of [001] and [100] dislocations is confirmed by microstructural observations. Simulation of gravity‐driven compaction process reveals extremely rapid compaction of kilometer‐scale crystal mush in the Poyi magmatic system. During the early compaction with high porosity, crystallographic habit of olivine may produce shape‐preferred orientation and the related B‐type fabric. In the final stage of compaction and crystallization, the initial shape‐preferred orientation was gradually overprinted, whereas the weak B‐type fabric has remained with dislocation creep and dislocation‐accommodated grain boundary sliding. Calculated seismic velocities of peridotite samples show low P and S wave anisotropies, with the fastest S wave polarization direction normal to the foliation. Hence, a mush‐dominated ultramafic intrusion exhibits weak seismic anisotropy, which has potential to better understand seismic anisotropy in the transcrustal magmatic systems.
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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 | 0.002 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 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".