Abstract: The East Kemptville tin-base metal deposit, Nova Scotia: documentation of the magmatic to hydrothermal transition in a highly-fractionated, F-rich environment
Bibliographic record
Abstract
The East Kemptville tin-base metal deposit, in operation from 1985–1992 as the only primary producer of tin in North America, is hosted by a 376 Ma topaz-muscovite leucogranite (EKlcgr). Mineralization (i.e., 56 Mt @ 1.65% Sn) occurred as structurally controlled, zonedand massive-, tin-topazsulphide greisens. Geochronological (Rb-Sr, 40Ar/39Ar, Pb-Pb, U-Pb, Re-Os) and petrological studies indicate that the EKlcgr represented the end product of crystal (Plg-Bt-Kfs)-fl uid fractionation of a zoned, peraluminous magma. This zoned magmatic complex, referred to as the Davis Lake Pluton, is one of several plutonic centres comprising the large (7800 km2), 380 Ma South Mountain Batholith. The EKlcgr (ca. 1 km2) was emplaced at ca. 3.5–4 kbar and represents the apical portion of a zoned, F-rich magma within which occurred periodic cycling of fl uid pressure. The preserved textures and petrological features that refl ect this once dominant process include: (1) gradation and heterogeneity of granitic textures inwards from the contact (i.e., roof ); (2) a variety of miaroles near the roof zone, some of which contain primary cassiterite; (3) distribution of paired aplite-pegmatite sheets; (3) crenulate layering and USTs marginal to the contact; (4) abundant stockscheider; and (5) an unfractionated chemistry (e.g., whole rock and Kfs)for pegmatite versus the host EKlcgr. Related to the cyclicity of fl uid pressure was emplacement of the EKlcgr into an active shearzone environment, evidence of which includes: (1) the elongate outline of the intrusion; (2) orientation of quartz grains in the EKlcgr and endogenic pegmatites; (3) stockscheider alignment; and (4) the structural control of mineralized greisens and veins (e.g., fi bre veins on growth faults). Stable isotopic data (O, D, S) and fl uid inclusion studies indicate that the magma evolved as a closed system with no evidence of second boiling (i.e., fl uid unmixing), the latter feature of which is commensurate with the depth of formation. The above observations are interpreted to suggest that the mineralized environment evolved due to injection of a volatile-rich, chemically-evolved (i.e., Sn-, Cu-, Zn-, F-rich) magma into a fault zone within which periodic pressure release related to seismic events facilitated exsolution of a mineralizing fl uid. Migration of this fl uid into structural sites (i.e., fractures) and its subsequent interaction with and neutralization by the wallrock EKlcgr resulted in the formation of zonedand massive greisens.
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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 | 0.000 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".