Geological, mineralogical and geochemical process controls on Ni tenor variations in the metasedimentary-hosted Thompson 1D orebody at Vale’s Thompson mine (T3), Northern Manitoba, Canada
Bibliographic record
Abstract
The Proterozoic Thompson Nickel Belt (TNB) contains rift-related mafic-ultramafic igneous rocks, in a collisional belt at the NW margin of the Archean Superior province in Northern Manitoba, Canada. The TNB hosts world class Ni-Cu-(PGE) mineralization, that has undergone polyphase deformation (D1 – D4) and upper amphibolite to lower granulite facies metamorphism, up to ~750ºC and 7.5 kbars (Lightfoot et al., 2017). Komatiitic magmas (1880 ± 5 Ma; Hulbert et al., 2005) fertile in Ni & PGE elements intruded Ospwagan Group metasedimentary sequences and through sulfur assimilation and segregation produced primary magmatic sulfides (Lesher and Burnham, 2001).\nThe TNB metasedimentary-hosted ores of the Thompson Deposit (T1 and T3) are interpreted to have formed from the complete remobilization and relocation of sulfides from primary ultramafic boudins (Bleeker, 1990). The aim of this study was to assess geological, mineralogical and geochemical controls on the Ni tenor of sulfide (% Ni normalized to 100% sulfide), and to understand why Ni tenor in the metasedimentary-hosted Thompson deposits is higher than those of primary ultramafic associated mineralization, like the Pipe and Birchtree Deposits. The research focused on the Thompson 1D orebody at T3 mine because of the large variability of nickel tenor, ranging from(8-16 wt% Ni).\nThe two most significant findings of this study are that; Ni-Co-Pd tenors are highest in shear-hosted massive sulfides and that there is a positive correlation between pyrite modal abundance and Ni-Co tenor. Pyrite is interpreted to be paragenetically-late, which strongly indicates a metamorphic modification of the ores. Understanding the processes responsible for pyrite generation is crucial to deconvoluting the cause of the Ni tenor variability across the Thompson 1D deposit.\nThis study is the first to document the occurrence of polymetallic sulfide melt inclusions (SMI) at Thompson, which indicates that partial melting of sulfide ores occurred during peak metamorphic conditions and modified the ores at Thompson.\nA staged mechanism for the formation of Thompson sulfide deposits is proposed, in which three principle stages exist: komatiitic emplacement and a primary magmatic origin for the sulfides; high P-T MSS reformation and repositioning of primary ultramafic sulfide, and partial melts, into sedimentary country rocks; and modification by hydrothermal fluids, contemporaneous localized partial melting, and shear-melting, which further modified the remobilized ores.\nResearch in this study has helped move the ore genesis models for Thompson forward and although nickel tenor upgrading of ores is not entirely explained, it seems to be related to pyrite and the late tectonic-metamorphic history of the deposit.
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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 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".