Using biotite composition of the Devonian Lake George granodiorite, New Brunswick, as a case study for W-Mo-Au-Sb mineralized magmatic hydrothermal systems
Bibliographic record
Abstract
The granodioritic Lake George polymetallic deposit is located approximately 35 km southwest of Fredericton, New Brunswick. This intrusion is a metaluminous to weakly peraluminous, calc-alkaline body that shows an evolved I-type, volcanic arc affinity. Based on an Early Devonian age determination, (412 +5/-4 Ma, zircon U-Pb) it is related to the Hakshaw granite phase of the Pokiok Batholith. The Lake George stock is cut by Hibbard stibnite -quartz veins and quartz-scheelite-molybdenite veinlets that contain significant amounts of gold. Fresh biotites from this intrusion were analyzed at both the core and rim by electron microprobe, and along rim to rim transects by laser ablation ICP-MS at the University of New Brunswick to build an understanding of the halogens responsible for mineralization and trace element distribution within this deposit. Biotites of this intrusion are reddish brown in colour (indicative of reduced I-type source) and mostly altered to chlorite. They usually contain apatite, zircon, titanite, ilmenite, rutile, and sulphide minerals as mineral inclusions. Temperature was calculated with the Ti-In-biotite geothermometer, in which the results showed a variation between 583 and 745°C. Two depths of emplacement were determined based on the Al in hornblende and biotite geobarometries confirming the porphyritic texture of this intrusion (4.3 and 1.5 km, respectively). Forming amphiboles at that depth clearly indicates a high water content of the source magma; in addition, hydroxyl is the most dominant component of the hydroxyl site (Average 1.89 wt%) in biotites. The limited range of IV(F/Cl) values of the Lake George biotites suggested that they all equilibrated with one fluid. Even though there is no noticeable difference in major elements from core to rims, evidence of magma evolution is recorded by biotite grains by their trace elements. For instance, Cu, Rb, Cr, K, Mo, Sn, Cs and W increase from core to rims, whereas Ba, Ni, Mn, and Li act inversely. Sb has a negligible variation from core to rim. Interestingly, the partition coefficient (biotite/whole-rock) is significantly small for Sb, W, and Mo (main associated mineralization) with 0.06, 0.28 and 0.13 in pure magmatic biotites and increase to 0.77, 1.93 and 0.20 in more altered biotites reflecting enrichment of these elements towards the late stage fluid. Based on these observations, the concept of using mica composition to help identify fertile Acadian magma systems was proved; this method may be a useful tool to indicate the difference between barren and mineralized granophileelement rich systems.
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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".