Rheic Ocean mafic complexes: overview and synthesis
Bibliographic record
Abstract
Abstract The Rheic Ocean formed during the Late Cambrian–Early Ordovician when peri-Gondwanan terranes (e.g. Avalonia) drifted from the northern margin of Gondwana, and was consumed during the collision between Laurussia and Gondwana and the amalgamation of Pangaea. Several mafic complexes, from the Acatlán Complex in Mexico to the Bohemian Massif in eastern Europe, have been interpreted to represent vestiges of the Rheic Ocean. Most of these complexes are either Late Cambrian–Early Ordovician or Late Palaeozoic in age. Late Cambrian–Early Ordovician complexes are predominantly rift-related continental tholeiites, derived from an enriched c. 1.0 Ga subcontinental lithospheric mantle, and are associated with crustally-derived felsic volcanic rocks. These complexes are widespread and virtually coeval along the length of the Gondwanan margin. They reflect magmatism that accompanied the early stages of rifting and the formation of the Rheic Ocean, and they remained along the Gondwanan margin to form part of a passive margin succession as Avalonia and other peri-Gondwanan terranes drifted northward. True ophiolitic complexes of this age are rare, a notable exception occurring in NW Iberia where they display ensimatic arc geochemical affinities. These complexes were thrust over, or extruded into, the Gondwanan margin during the Late Devonian–Carboniferous collision between Gondwana and Laurussia (Variscan orogeny). The Late Palaeozoic mafic complexes (Devonian and Carboniferous) preserve many of the lithotectonic and/or chemical characteristics of ophiolites. They are characterized by derivation from an anomalous mantle which displays time-integrated depletion in Nd relative to Sm. Devonian ophiolites pre-date closure of the Rheic Ocean. Although their tectonic setting is controversial, there is a consensus that most of them reflect narrow tracts of oceanic crust that originated along the Laurussian margin, but were thrust over Gondwana during Variscan orogenesis. The relationship of the Carboniferous ophiolites to the Rheic Ocean sensu stricto is unclear, but some of them apparently formed in a strike-slip regimes within a collisional setting directly related to the final stages of the closure of the Rheic Ocean.
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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 | 0.002 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.018 | 0.028 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.003 |
| Open science | 0.001 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.015 | 0.003 |
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".