THE TANCO PEGMATITE AT BERNIC LAKE, MANITOBA. XVI. ZONAL AND BULK COMPOSITIONS AND THEIR PETROGENETIC SIGNIFICANCE
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
The Tanco pegmatite deposit at Bernic Lake, in southeastern Manitoba, is a virtually completely hidden, essentially undeformed, subhorizontal, bilobate, saddle-shaped body ~1520 m long, 1060 m wide and up to ~100 m thick. The highly fractionated pegmatite of the LCT family, rare-element class, petalite subtype, consists of nine internal zones. The outer zones are concentric, whereas the layered inner zones are segmented and locally complex in shape. A 3D computer model representation of the pegmatite assisted in calculation of volumes and compositions of individual zones and of the whole pegmatite, based on 102 km of 1355 drill-hole intersections, underground observations, measured and estimated mineral modes of the zones, zone-specific compositions and densities of minerals, and ore grades. The early outer zones tend to show granitic modes, but the inner zones strongly deviate in proportions of feldspars, or by high enrichment in lithium minerals, and some of the zones are virtually monomineralic. The bulk mode of Tanco is granitic, except ~9 vol.% petalite (including spodumene + quartz pseudomorphs). Despite also being economically significant for Cs, Ta and Li, the pegmatite contains less than 1 vol.% of any other non-micaceous minerals, and less than 0.1% of most of them. The bulk chemical composition closely reflects the modal relationships: it is peraluminous, and granitic, with prominent enrichment in Li, Rb, Cs and F, moderate contents of Tl, Be, B, Ga, Sn, Nb and Ta, and remarkable depletion in Fe, Mn, Mg, Ca, Ba, Sc, Ti and Zr. A very high degree of fractionation is shown for the bulk pegmatite by the values K/Rb 4.7, K/Cs 9.3, Rb/Cs 2.0, Rb/Tl 137, Fe/Mn 0.63, Mg/Li 0.02, Al/Ga 917, Zr/Hf 2.6, Zr/Sn 0.21 and Nb/Ta 0.19. Zonal and bulk chemical composition is in rough agreement with the experimental thermal trough in the system Ab + Qtz + Ecr at 2 kbar P(H2O), but shifted toward the Ab apex by elevated B, P and F, and by the voluminous wall-zone. The composition of the wall zone (20) is remarkably similar to that of bulk Tanco, except for the elevated contents of rare elements in the latter that are concentrated in the intermediate and inner zones. In turn, zone (20) is very close to the composition of nearby, somewhat less fractionated peraluminous leucogranites that are parental to local genetically related pegmatite groups. The wall zone (20), which composes 44 vol.% of Tanco, represents by analogy a petrogenetic link between an undisclosed parent leucogranite and the Tanco deposit. These relationships document derivation of the Tanco pegmatite and its analogues elsewhere by igneous differentiation from a fertile leucogranitic magma.
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.
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 it