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<b>Titanomagnetite Rims on Hornblende Phenocrysts in Intermediate Subvolcanic Intrusions, Torud–Ahmad Abad Magmatic Belt, Iran: Examination of</b> <b>Devolatilization and Oxidation Processes</b>

2025· article· en· W4407033326 on OpenAlex

Why this work is in the frame

A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.

affAt least one author lists a Canadian institution in the pinned OpenAlex snapshot.

Bibliographic record

VenueLithosphere · 2025
Typearticle
Languageen
FieldEarth and Planetary Sciences
TopicGeological and Geochemical Analysis
Canadian institutionsUniversity of New Brunswick
Fundersnot available
KeywordsPhenocrystGeologyGeochemistryHornblendeAndesitePyroxeneFelsicDioriteMaficVolcanic rockDaciteIgneous rockPetrologyOlivineBiotiteQuartzZirconVolcano

Abstract

fetched live from OpenAlex

Abstract Mafic to felsic adakitic intrusive and extrusive rocks in the Torud–Ahmad Abad magmatic belt occur south-southeast of Shahrood (north of the Central Iran Zone). These adakites, in the form of dykes and other hypabyssal igneous bodies, are emplaced into late Neoproterozoic amphibolite and mylonitized granites and a thick sequence of Paleocene to middle Eocene volcanic and volcano-sedimentary rocks. These high silica and low silica adakites (HSA and LSA) span a range of lithologies including basaltic andesite, andesite, trachyandesite, dacite, trachydacite, and dacite. The adakites are composed mainly of calcic pyroxene, Ca-Na amphibole, and plagioclase phenocrysts, with minor biotite and titanomagnetite. In these intrusions, iron-titanium oxides crystallized late (within the groundmass) or occur as secondary phases. One of the interesting features of these rocks is the opacitization (magnetite rich selvage) of ferromagnesian phenocrysts, such as hornblende, which is a localized replacement reaction. The intensity and color of these opacitized margins depend on the extent of titanomagnetite-magnetite formed. The SEM-EDS analysis results show that most of magnetite formed at temperatures &amp;gt;500°C related to pressure quenching of the melt due to emplacement and differential volcanic degassing. The phenomenon of opacitization is due to decreasing stability of Fe2+ and hydrous ferromagnesian phenocrysts, such as amphiboles, to form less hydrous to anhydrous pseudomorphs (selvage) in the near-surface environment with oxidative reactions linked to pressure quenching and differential devolatilization of H2 from the melt during hypabyssal emplacement. The rapid decrease in pressure during magma ascent causes hornblende instability and thus helps to create these opaque rims (opacitized) on ferromagnesian phases (magnetite and titanomagnetite-rich assemblage). Hornblende breakdown - destabilization increases due to melt degassing - devolatilization [decrease in P(H2O)] during the process of ascent—emplacement with reduction of magmatic total pressure (decompression) and/or melt oxidation due to differential degassing of H2.

Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.

Full frame distilled prediction

Teacher imitation

Not 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.

metaresearch head score (Codex)0.000
metaresearch head score (Gemma)0.000
Version: codex-gemma-dda1882f352aValidation status: machine_predicted_unvalidated
Candidate categoriesInsufficient payload (model declined to judge)
Consensus categoriesnone
DomainCandidate signal: none · Consensus signal: none
Study designCandidate signal: Observational · Consensus signal: Observational
GenreCandidate signal: Empirical · Consensus signal: Empirical
Teacher disagreement score0.125
Threshold uncertainty score1.000

Codex and Gemma teacher scores by category

CategoryCodexGemma
Metaresearch0.0000.000
Meta-epidemiology (narrow)0.0000.000
Meta-epidemiology (broad)0.0000.000
Bibliometrics0.0000.001
Science and technology studies0.0000.000
Scholarly communication0.0000.000
Open science0.0000.000
Research integrity0.0000.000
Insufficient payload (model declined to judge)0.0010.000

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.

Opus teacher head0.007
GPT teacher head0.199
Teacher spread0.193 · how far apart the two teachers sit on this one work
Validation statusscore_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it