Magmatic recharge during formation and resurgence of the Valles caldera, New Mexico, USA: evidence from quartz compositional zoning and geothermometry
Bibliographic record
Abstract
The Valles caldera complex in north-central New Mexico, USA, represents the type example of resurgent caldera system, characterised by eruption of two voluminous high-silica rhyolite ignimbrites (the Otowi and Tshirege Members of the Bandelier Tuff) at 1.608 ± 0.010 Ma and 1.256 ± 0.010 Ma, respectively. Refined dating has shown that resurgence occurred shortly after eruption of the Tshirege, or Upper Bandelier Tuff (UBT). Central resurgence of ~1000 m was accompanied by small-volume eruptions of the Deer Canyon Rhyolite, followed closely by the Redondo Creek Rhyodacite. The Cerro del Medio Rhyolite lava dome complex is a product of ring fracture volcanism following resurgence, erupting at 1.229 ± 0.017 Ma. A central aim of this study was to find evidence for magmatic recharge during this geologically short (~ 27 ka) time period. We have combined cathodoluminescence (CL) imaging and titanium-in-quartz geothermometry techniques to individual quartz crystals from 1) different stratigraphic horizons of the UBT ignimbrite, 2) samples of the Deer Canyon Rhyolite and 3) the Cerro del Medio Rhyolite lavas. CL imaging reveals that ~80% of the erupted volume UBT ignimbrite contains unzoned quartz crystals (average concentration = 28 ± 2 ppm Ti), recording relatively isothermal temperatures of 647-696 °C. An abrupt occurrence of compositionally zoned quartz crystals ) within the mid-to-late erupted UBT ignimbrite units 3-5 reveals evidence for interaction with hotter magma. Corresponding titanium-in-quartz measurements of outer, bright CL rims (71 ± 9 ppm Ti) reveal temperature increases of ~100 °C relative to the start of the UBT eruption. We have discovered an interesting heterogeneity within the Deer Canyon Rhyolite lavas, with strong spatial control on eruption of porphyritic lavas containing complexly zoned quartz crystals onto the western regions of the resurgent dome. Conversely, crystal-poor to aphyric lavas containing small, unzoned quartz crystals are conf
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| 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".