Geology and Au enrichment processes at the Paleoproterozoic Lalor auriferous volcanogenic massive sulphide deposit, Snow Lake, Manitoba
Bibliographic record
Abstract
The Paleoproterozoic Lalor auriferous volcanogenic massive sulphide deposit, located in the Snow Lake mining camp, Manitoba, is hosted in a complex volcanic package referred to as the Lalor volcanic succession. The deposit consists of stratigraphically and structurally stacked Zn-rich, Au-rich, and Cu-Au-rich ore lenses. The host volcanic succession comprises mafic to felsic tholeiitic to calc-alkaline extrusive to intrusive volcanic rocks of the ca. 1.89 Ga Lower Chisel subsequence, and the ore is hosted in both mafic and felsic rocks. Atypical of the other Zn-rich deposits of the Snow Lake district, the Lalor deposit is not situated at the top of the Lower Chisel subsequence, but is at a slightly lower stratigraphic position. The volcanic rocks that host the deposit were affected by intense and laterally extensive ore-related hydrothermal alteration. These altered rocks were subsequently subjected to syndeformational amphibolitegrade metamorphism that resulted in the development of distinct minerals and metamorphic mineral assemblages of varying composition from variably altered precursor lithologies. Five distinct alteration- and metasomatism- related chemical associations (K, K-Mg-Fe, Mg-Fe, Mg-Ca, and Ca) are recognized based on mineralogical (mineral assemblages) and bulk geochemical compositions. Mapping of the host volcanic rocks and ore-related mineral assemblages and chemical associations at Lalor indicates the following: 1) the Zn-rich massive sulphide lenses are preferentially associated with the low- to high-temperature K and Mg- Ca alteration zones; 2) the Cu-Au-rich zones, which occur at depth, stratigraphically below the Zn-rich mineralization, are hosted in transposed, presumably originally discordant high-temperature Mg-Fe altered rocks; and 3) Au has been in part locally remobilized into low-strain sites that are not now spatially associated with any particular chemical association. The Lalor volcanic succession is affected by polyphase deformation that has strongly influenced the geometry of the Lalor deposit. Pre-D2 (synvolcanic?) deformation is evidenced by the abrupt termination of the intensely altered Lalor volcanic succession to the southwest and the presence of chemically distinctive and unaltered volcanic rocks of the Western succession. The present geometry of the deposit is largely controlled by D2 deformational structures with important stretching (L2), flattening (S2), and structural staking (F2 folding and syn- to late-D2 transposition and shearing). The D2 deformation and associated peak metamorphic conditions are thought to be responsible for the local remobilization of Au sulphosalts and some sulphides.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 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".