Origin of Antecrysts in Igneous Rocks from the Salavat Range (NW Iran): an Explanation for the Geochemical Signature of Potassic Alkaline Rocks
Bibliographic record
Abstract
Abstract Abundant silica-undersaturated potassic lavas are found in the centre of the Turkish–Iranian plateau (NW Iran) as flows, pillows and dykes. They display abundant zoned clinopyroxene macrocrysts and xenoliths of igneous cumulates. We determined four types of zoned crystals (Type-I, -II, -III and -IV) on the basis of their composition and zoning patterns. Use of in situ compositional data, together with whole-rock major and trace elements and the isotopic signatures of the host lavas provided evidence for the derivation of the different types of zoned clinopyroxenes from at least two contrasting parental melts. Our findings are consistent with an origin of the ultrapotassic and sodic alkaline melts from the deep-seated compaction pockets inferred from our previous studies of the alkaline magmatism throughout the Turkish–Iranian plateau. The ultrapotassic melt, which accumulated at the top of the compaction pockets, eventually ponded close to the spinel–garnet mantle transition and generated colourless antecrysts (Type-I and Type-II) and clinopyroxenite cumulates. When the compaction pocket impinged on the continental lithosphere, interstitial melts segregated and flowed inside dykes where grass green antecrysts (Type-III) and zoned phenocrysts (Type-IVa) crystallized from a melt having a geochemical signature of sodic alkaline melt. Later, at the crustal level, melt crystallization processes produced Type-IVb zoned phenocrysts. Our results are at odds with the paradigm of potassic magmas in NW Iran being derived strictly from a single mantle source.
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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 | 0.002 | 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) | 0.001 | 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".