Multi-Phase Tectonic and Volcanic Evolution of a Nascent Backarc Rift: Impacts of Spreading Centre Reorientation, Subduction Reversals, Ridge Collisions, and Asymmetric Slab Rollback on the Northern New Hebrides Backarc
Bibliographic record
Abstract
Intra-oceanic backarc are characterized by crustal accretion along seafloor spreading axes; however, little is known about the initial rifting of the over-riding plate prior to the establishment of stable seafloor spreading. To address this knowledge gap, we investigate the ~3.5 Ma backarc troughs in the New Hebrides Subduction Zone. Using available bathymetric data, we developed remote-predictive geologic maps at a scale of 1:100,000 over an area of ~234,000 km2. Interpretation of seafloor morphologies, lineament analyses of seafloor fabric, fault kinematics revealed by earthquake moment tensor data, and cross-cutting relationships demonstrate distinct stress regime changes during sequential backarc rifting. South of 10.5°S, three phases of backarc opening are identified: 1) Initial arc rifting accommodating clockwise rotation of the arc, ~3.5–2.7 Ma (preserved in the Duff Horst and Graben Domain); 2) East-west-directed rifting and incipient seafloor spreading, ~2.7–1.1 Ma (preserved in the Jean Charcot Troughs); 3) Northeast-southwest- to NNE-SSW-directed rifting and counter-clockwise rotation of the arc, ~1.1 Ma-present (preserved in the actively rifting Santa Cruz Troughs). Two prominent roughly east-west oriented backarc volcanic corridors stretch from the relict arc and track arc migration along deep crustal-scale structures. North of ~10.5°S, two grabens formed from a single rift event occurring before the crustal scale ruptures that severed the Reef Islands Platform from the New Hebrides Arc. The outcome of this work reveals new insights in the geodynamic processes that bridge periods of stable subduction with the formation of mature backarc basins with crustal accretion occurring along spreading axes.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.002 | 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 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".