Using biotite composition of the Devonian Mount Elizabeth Intrusive Complex, New Brunswick, as a proxy for magma fertility and differentiation in W-Mo-Au-Sb mineralized magmatic hydrothermal systems
Bibliographic record
Abstract
The Early Devonian (418 ± 1 Ma, monazite U-Pb) Mount Elizabeth intrusive complex, New Brunswick, Canada, is a multiphase metaluminous to weakly peraluminous, high K calc-alkaline body that shows within plate affinity. The complex consists of apparently contemporaneous igneous suites including a mafic suite, an eastern peraluminous granite suite and a western alkali granite suite. The eastern part comprises compositionally and texturally homogenous biotite granite, whereas the western part is mostly heterogeneous and contains five different units. The most abundant phase of the western suite is medium- to coarse-grained alkaline equigranular granite. This complex poorly exposed so that most of the available data, including inferred contact relationships, is based on geophysical data. It should be added that no mineral occurrences have been reported so far from this complex. Fresh biotite from this intrusion was analysed from core to rim by electron microprobe, and laser ablation ICP-MS at the University of New Brunswick to test whether biotite preserves a record of magma evolution in terms of major and trace-element and halogen compositional variations. Subhedral to elongate biotite phenocrysts are less than 700 ?m long and reddish brown in colour indicative of a reduced I-type source. A calc-alkaline affinity is also suggested by biotite major element classification schemes. Biotite is locally altered to chlorite along cleavage planes, and typically contain iron oxides, monazite, ilmenite, apatite, xenotime, and zircon as mineral inclusions. Results of electron microprobe and laser ablation ICP-MS studies indicate that biotite grains are homogenous in major elements; however, they show variation in trace elements from core to rim. The biotite grains investigated have the highest Sn, W, Sb, and Mo concentrations recorded thus far among Devonian-related granitoid intrusions of New Brunswick (130, 40, 1, 3 ppm, respectively). There is no systematic correlation between major elements including FeTot, or FeTot/Ti and any of these trace elements. To further study trace-element distribution, a biotite from each of the phases was mapped with laser-ablation ICP-MS revealing patchy Ba, Rb, and Cs zoning. These patterns are interpreted to be a result of localized hydrothermal alteration and intracrystalline volume diffusion in these biotite grains. The intracrystalline distribution of Sn, W, Mo and Sb is homogeneous. Furthermore, halogen contents analysed by EPMA indicate that hydroxyl is the dominant component of hydroxyl site followed by fluorine. It also showed that these biotites formed from strongly contaminated and reduced I-type granite. As a result, high concentration of Sn in biotite is interpreted to be caused by crustal contamination, and lowtemperature hydrothermal processes (sub-solidus) rather than being magmatic in origin.
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.
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 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 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".