Petrology And Origin Of Crustal Xenoliths From Tumalo Cinder Cone, Central Oregon Cascades
Bibliographic record
Abstract
Tumalo Cinder Cone, a Quaternary High Cascades volcanic center located about 8 km southwest of Bend, OR, is well-known for its crustal xenoliths. The goal of this study is to characterize the petrology of these xenoliths and gain insight into the nature of the crust beneath central Oregon in an area near the inferred edge of the Columbia Embayment. Specifically, we seek to determine whether these xenoliths were derived from: (1) pre-Tertiary rocks at the western edge of the continent, (2) Oligocene-Miocene intrusions associated with Western Cascades magmatism, or (3) Pliocene or younger plutons associated with High Cascades volcanism. Approximately 40 xenoliths have been collected; they range between 3 cmX2 cm and 11 cmX7 cm size and weigh between 4 and 510 grams each. All appear to be broadly granitic in composition (quartz diorite-granodiorite) and many appear to have undergone partial melting during ascent as evidenced by their vesicular textures and the presence of mixing textures at the margins. Chemical analysis by XRF and ICP-MS indicate the xenoliths range from 63-79 wt.% SiO (sub 2) and are moderately LREE enriched (La (sub N) = 80-90; La/Yb (sub N) = 4.4-5.0; Eu/Eu* = 0.4-0.2). Spidergrams indicate the xenoliths originated in a subduction zone setting. Relative to data from Miocene granitic rocks in the Western Oregon Cascades, the Tumalo xenoliths have systemically lower CaO and higher Na (sub 2) O at equivalent SiO (sub 2) . A trend toward lower CaO/Na (sub 2) O with decreasing age has been observed among data from Cascade plutonic and volcanic rock, suggesting that these xenoliths are younger than Miocene. Zircons separated from one xenolith are being dated by LA-ICP-MS to further test this conclusion.
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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 | 0.000 | 0.000 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".