Magmatic mica and its potential as an indicator of magma fertility in the granitoids of New Brunswick
Bibliographic record
Abstract
The mineralized intrusions of New Brunswick are related to crustal growth processes that occurred during Acadian Orogeny, post Acadian uplift, and Neo-Acadian Orogeny. They were emplaced pre-, syn-, late-, and post-tectonically between 423 and 360 Ma. These intrusions have affinities ranging from primitive to highly evolved A-, S-, and I-types granitoids, and are associated with Sn, Ta, Li, Sb, W, Mo, Cu, and Au, as well as basemetals and U mineralization. Biotite crystallizes over a wide range of conditions and reacts very sensitively to physiochemical conditions of the magma; this sensitivity makes mica a great mineral for identifying the petrogenetic, mineralization, and alteration processes of the host granitic rocks. The following features make biotite a valuable probe of magma composition: 1) it is the most important reservoir of any excess aluminium in granites that do not contain modal garnet, cordierite, or the Al2SiO5 polymorphs; therefore, it directly reflects the peraluminosity of the host magma in such rocks; 2) it is the most readily available indicator of oxidation state; and 3) it can provide information about the F and Cl content of the magma. Mineralized and barren rocks are characterized by different chemical variations in biotite. For instance, mineralized biotite is characterized by lower Mg and Ti contents relative to biotite from barren rocks; they also have higher amount of Al comparing to biotite from barren phases. Several studies have shown that biotite, continuously equilibrates with the host liquids. Therefore, core-to-rim study of this mineral and its compositional zoning may provide a record of magma evolution so that the origin and evolution of granitoids can be discerned. Furthermore, the chemical composition and the colour of this mineral strongly reflects the tectonic origin of its host. For instance, the bright red colour of biotite indicates peraluminous collisional granitic pluton and reflects a high total Fe content with low Fe3+/(Fe2+ + Fe3+) and probably the presence of Ti4+. In part this study aims to calculate fluoride and chloride activity of aqueous fluids based on F and Cl contents in the minerals containing hydroxyl and halogens determined by combined electron microprobe and LA ICP-MS analysis. The final data will be compared to the whole rock geochemistry. These results are expected to help constrain crystallization conditions, volatile exsolution and fluorine-chlorine activity of fluids associated with these intrusions. They should also indicate the degree of subsolidus re-equilibration via various geothermobarometry techniques.
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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 | 0.004 | 0.003 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".