Modeling the growth of laccoliths and large mafic sills: Role of magma body forces
Bibliographic record
Abstract
[1] The use of elastic plate theory to model the emplacement of laccoliths and large mafic sills has been debated for nearly 40 years. These intrusions typically attain a horizontal width that is large relative to the emplacement depth. Provided that large-scale plasticity and/or heterogeneity is not observed in the overlying host rock, it should then be valid to approximate its deformation based on analysis of a thin elastic plate with effective properties that are the consequence of interaction among heterogeneities that are small relative to the size of the intrusion. But the predictions that are usually cited from elastic plate theory are characterized by bell-shaped geometry, in contrast to the flat-topped, steep-sided geometry typical of many laccoliths or the nearly uniform thickness typical of large mafic sills. This fact has motivated several alternate explanations of laccolith and large mafic sill emplacement. Nonetheless, elastic plate theory should be revisited in light of the fact that previous elastic plate-based predictions have, in general, not taken into account an appropriate fracture propagation condition, fluid flow in the growing intrusion, and, importantly, the influence of the weight of the magma on intrusion growth. We present a model for the growth of circular intrusions that accounts for all of these factors. The model predicts the appropriate geometry for both laccoliths and large mafic sills. The predicted thickness to length relationships are also consistent with field data. Hence, while it may sometimes be appropriate, there is, in general, no fundamental need to appeal to large-scale rock plasticity in order to explain observed intrusion geometries, and it may, in fact, be appropriate to understand the growth of laccoliths and large sills in light of a single underlying mechanical model.
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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 | 0.001 | 0.001 |
| 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) | 0.002 | 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".