Bibliographic record
Abstract
A large number of Late Precambrian calc-alkalic epidote-bearing granitoids are found in the Central Structural Domain (CSD) - which comprises three segments: Serido Fold Belt (SFB), Cachoeirinha-Salgueiro Fold Belt (CSF), and Riacho do Pontal Fold Belt (RPF) - and in some other localities in Northeast Brazil. In the CSF, meta to peraluminous, epidote-bearing granodiorites and tonalites intruded phyllites around 620 Ma ago, while in the SFB a larger variety of plutons with igneous epidote intruded Jucurutu gneisses and Serido schists. Two-mica granodiorites with (±) garnet and igneous epidote (?) intruded amphibolite-grade metasediments of the RPF. Magmaric epidote is also present in tcondhjemitic and shoshonitic plutons that intruded, respectively, Salgueiro schists and basement rocks along the southern boundary of the CSF, as well as in plutons in the Surubim-Caroalina complex, Pajeu-Paraiba and Sergipean Fold Belts. It is found in four textural relationships, two of which indisputably magmatic and two others of sub-solidus reactions. In the CSF, epidote-bearing granitoids solidified, with one exception, around 6 kbar - 7 kbar, according to their Al contents in hornblende. Lower pressures obtained for quartz diorite enclaves are due to Al loss through sub-solidus reaction with plagioclase producing granular epidote. They differ from similar Mesozoic granitoids in North America because, although their pressures of solidification are high, they intruded greenschist fades metasediments likewise Paleozoic plutons in Argentina (Pampean Ranges), New England (Sherbrooke-Lewiston area) and Nov Zealand (Victoria Ranges). In the CSF, these granitoids exhibit moderate Sr, Ba and Zr, low Nb (<20 ppm), are LREE-enriched and HREE-depleted, with variable negative Eu anomaly. In the SFB (e.g. Sao Rafael batholith,), granitoids are higher in Sr, with Ba contents equivalent to the CSF granitoids, Zr slightly higher and low Nb. They exhibit less sterep REE-patterns and lack Eu anomaly. In the RPF, granitoids display Sr, Ba and Nb contents equivalent to those in the CSF, Zr twice as high, and REE patterns with negative slope - lacking or exhibiting a discrete Eu anomaly. Epidote - bearing plutons in the CSF exhibit high δ 18 O (11 permil - 13 permil), and amphibplite xenoliths, probably from the source, have δ 18 O around 10.5 permil. Equivalent plutons in the SFB display δ 18 O) values (6 permil - 8 permil) slightly lower than those typical for epidote-bearing tonalites and trondhjemites in northwestern North America (7.5 permil - 9.0 permil, e.g., Hazard Creek Complex, Idaho). This demonstrates that epidote-bearing plutons originate from more than one kind of source material, always in the presence of a component in the magma derived from sedimentary or altered volcanic rocks. Processes leading to their formation are repeated through geological time and magmas intrude different crustal levels.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot 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.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.003 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.008 |
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; both teacher heads agree on what is shown here.
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".