Tonalite–Trondhjemite and Leucogranodiorite–Granite Suites From the Rio Maria Domain, Carajás Province, Brazil: Implications For Discrimination and Origin of the Archean Na-Granitoids
Bibliographic record
Abstract
Abstract The Mesoarchean Na-granitoids exposed in the Rio Maria domain, southeastern Amazonian craton, are represented by tonalite–trondhjemite and leucogranodiorite–granite suites. The 2.98–2.92 Ga tonalite–trondhjemites are the most voluminous rock type in the Rio Maria domain and host 2.86 Ga leucogranodiorite–granite plutons. These rocks share common geochemical characteristics, such as relatively high Al 2 O 3 and Na 2 O and low Yb and Y contents, as well as the behavior of the REE. However, based on an extensive geochemical data set, it is possible to show that the leucogranodiorite–granites have higher K 2 O, Ba, Sr, and Rb and lower CaO contents than the tonalite–trondhjemites. The latter are compositionally similar to typical tonalite–trondhjemite–granodiorite (TTG) series and probably originated from partial melting of garnet amphibolites, derived from tholeiitic rocks or from metabasalts of the Identidade greenstone belt, at pressure conditions suitable to produce high, medium, and low La/Yb tonalite–trondhjemite groups. The leucogranodiorite–granites show geochemical affinity with the Transitional TTG of the Yilgarn craton and are related to the Hybrid granitoid group. The ambiguous geochemical character of the Rio Maria leucogranodiorite–granite suite, which shares some characteristics that are typical of the tonalite–trondhjemite rocks and others more commonly observed in the sanukitoid suites, may be related to complex processes involving TTG and sanukitoid magmas. The discrimination of these two Na-granitoid groups helps us estimate the true volume of TTG magmatism in the Rio Maria domain and in understanding the dynamics of petrogenetic processes in the terrane at the end of the Archean.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".