CARBONATITES FROM A LAMPROPHYRIC DYKE-SWARM, SOUTH WESTLAND, NEW ZEALAND
Bibliographic record
Abstract
A late Oligocene – early Miocene alkali lamprophyre dyke swarm was emplaced in western South Island, New Zealand, during transtensional development of the Alpine Fault plate boundary. Intrusive rocks comprise ultramafic and feldspathic lamprophyres, tinguaites, trachytes and carbonatites, the evolved members of which cause intense local fenitization of the country rock, producing aegirine–riebeckite schists. Carbonatites show a wide range of compositions from calcite- through dolomite–ankerite- to siderite- and norsethite-rich varieties. Carbonates and phosphocarbonates of Sr, Ca–Sr, Ca–Ba and REE occur in accessory amounts. Ratios of Sr, Nd, and Pb isotopes and nodule petrology indicate magma derivation from a previously metasomatized source in a part of the mantle dominated by the FOZO component. Very restricted ranges in radiogenic and stable isotope values indicate that all members of the swarm are cogenetic. Efficient fractional crystallization of a camptonite-producing magma yields a phonolitic or tinguaitic residuum that then separates immiscibly to form carbonatitic magma. Not all carbonatites are derived from a single lineage, so immiscibility may operate repeatedly during late fractionation. The final stages of carbonatite evolution (<400°C) are dominated by carbothermal processes, during which the carbonatites and associated silicate rocks develop a LREE-depleted, MREE-enriched pattern.
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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 | 0.000 |
| 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".