Origin of volcanic seamounts at the continental margin of California related to changes in plate margins
Bibliographic record
Abstract
Volcanic samples collected with the Monterey Bay Aquarium Research Institute's ROV Tiburon from eight seamounts at the continental margin offshore central to southern California comprise a diverse suite of mainly alkalic basalt to trachyte but also include rare tholeiitic basalt and basanite. All samples experienced complex crystal fractionation probably near the crust/mantle boundary, based on the presence in some of mantle xenoliths. Incompatible trace elements, poorly correlated with isotopic compositions, suggest variable degrees of partial melting of compositionally heterogeneous mantle sources, ranging from MORB‐like to relatively enriched OIB. High‐precision 40 Ar/ 39 Ar ages indicate episodes of volcanic activity mainly from 16 to 7 Ma but document one eruption as recent as 2.8 Ma at San Juan Seamount. Synchronous episodes of volcanism occurred at geographically widely separated locations offshore and within the continental borderland. Collectively, the samples from these seamounts have age ranges and chemical compositions similar to those from Davidson Seamount, identified as being located atop an abandoned spreading center. These seamounts appear to have a common origin ultimately related to abandonment and partial subduction of spreading center segments when the plate boundary changed from subduction‐dominated to a transform margin. They differ in composition, age, and origin from other more widespread near‐ridge seamounts, which commonly have circular plans with nested calderas, and from age progressive volcanoes in linear arrays, such as the Fieberling‐Guadalupe chain, that occur in the same region. Each volcanic episode represents decompression melting of discrete enriched material in the suboceanic mantle with melts rising along zones of weakness in the oceanic crust fabric. The process may be aided by transtensional tectonics related to continued faulting along the continental margin.
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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 | 0.001 |
| 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) | 0.006 | 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".