Characterization of barren and mineralized hydrothermal systems in an impact structure: the granophyre unit and footwall of the Sudbury Igneous Complex, Ontario, Canada
Bibliographic record
Abstract
The Sudbury Igneous Complex (SIC) is the product of a differentiated impact melt sheet and one \nof the best preserved impact sites globally. The top 1.5 km of the 2.5 km-thick crystallized melt \nsheet, referred to as the granophyre unit (GR), exhibits strong textural, mineralogical, \ngeochemical, fluid inclusion, and oxygen isotopic evidence for a long and complex hydrothermal \nhistory. This hydrothermal system has not previously been documented, and is characterized by \nan early magmatic-hydrothermal stage that has been overprinted by a later hydrothermal stage. \nThe magmatic-hydrothermal stage was dominated by fluids exsolved from the GR and resulted \nin pervasive saussuritization of plagioclase, alteration of alkali feldspar and plagioclase to endmember \ncompositions, and precipitation of epidote and muscovite in pits and void spaces. The \noverprinting hydrothermal stage was dominated by modified seawater sourced from the \nhydrothermal system in the overlying Onaping Formation and produced a pervasive alteration \nassemblage characterized by epidote, ferro-actinolite, stilpnomelane, biotite, and titanite with \nlesser muscovite, chlorite, and ferrotschermakite. The results from this study record a previously \nunidentified complex and protracted post-crystallization history of fluid-rock interaction for the \nGR that is related to the ore-forming hydrothermal system in the overlying Onaping Formation. The relationship between the hydrothermal system in the GR and the mineralized systems in the \nfootwall to the Sudbury Structure (SS) has not previously been established. The Nickel Rim \nSouth (NRS) Cu-Ni-PGE deposit, located in the east range of the Sudbury Structure, Ontario, \nrecords textural and geochemical evidence of a complex, multi-stage hydrothermal history and \nprovides an excellent comparison to the GR. Results from fluid inclusion petrography and \nmicrothermometry are used in conjunction in order to characterize the hydrothermal system at NRS. The combined results of fluid inclusion petrography and microthermometry, evaporate \nmound analysis, oxygen isotopic values of quartz, and trace element chemistry of alteration \nminerals reveal a complex hydrothermal history at NRS related to the cooling SIC, which \ncontributed to hydrothermal remobilization of metals into the footwall. The hydrothermal fluids \nare notably different from fluids documented in other mineralized footwall systems that are \nrepresented by high temperature, multi-solid fluid inclusions inferred to be critical for ore \nremobilization. Instead, the hydrothermal system at NRS shares more similarities with the GR \nhydrothermal system, bringing into question the role of fluids represented by high temperature, \nmulti-solid inclusions in ore remobilization.
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How this classification was reachedexpand
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 | 0.000 | 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 teacher head, 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".