New constraints on the magma distribution and composition beneath Volcán Uturuncu and the southern Bolivian Altiplano from magnetotelluric data
Bibliographic record
Abstract
Magnetotelluric (MT) data were used to create a three-dimensional electrical resistivity model of the Altiplano-Puna magma body (APMB) in the area surrounding Volcán Uturuncu in southern Bolivia. This volcano is at the center of a zone of surface deformation with a diameter of 150 km and persistent inflation of ∼10 mm/yr. Low electrical resistivities (<3 Ωm) at a depth of 14 + 1/–3 km below sea level (16–20 km below surface) are interpreted as being due to the presence of andesite melts in the APMB, and require a minimum melt fraction of 15%. The upper crustal resistivity structure is characterized by finite-length, dike-shaped conductors, oriented approximately east-west near sea level. A combination of dacite partial melts and aqueous fluids is required to explain the observed low-resistivity values. Geodetic data do not require any deformation in these shallow regions. The geometry of the upper surface of the APMB beneath Volcán Uturuncu is consistent with that predicted by geodynamic models that suggest that the APMB bulges upward directly beneath Volcán Uturuncu, near the measured inflation center (∼3 km west of Volcán Uturuncu). Viscosity estimates from the MT-derived resistivity model gives a maximum value of 1016 Pa·s and is consistent with models that propose diapir-like ascent of magma above the APMB. Resistivity models are compared and quantitatively correlated to seismic velocity models, showing good agreement on the spatial extent and depth of the APMB. A forward modeling study shows that the small differences in the depth to the top of the APMB between the different geophysical methods could be explained by variations in the composition of the magma body.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.002 | 0.001 |
| 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".