The Renard 4 kimberlite : implications for ascent of kimberlites in the shallow crust
Bibliographic record
Abstract
Kimberlite rock types that compose the Renard 4 kimberlite in northern Quebec, Canada, record the transition between the root and diatreme zones of a Class 1 kimberlite pipe. Analysis of lithologic textures and the componentry (clasts, macrocrysts and groundmass) of these rock types provides information pertinent to describing the evolution of the kimberlite pipe as well as to understanding the dynamics of its emplacement. This study defines six rock types present in the Renard 4 kimberlite. Five of these are kimberlitic. The rock types include two volcaniclastic facies, coherent kimberlite, transitional kimberlite and country rock breccia. The two volcaniclastic facies are: 1) a tufiisitic kimberlite breccia facies which is further subdivided into four phases and 2) an 'accretionary' magmaclastic facies. Coherent kimberlite is divided into two subfacies: 1) massive coherent macrocrystic kimberlite and 2) macrocrystic kimberlite breccia. The coherent breccia is a contact zone of the massive coherent kimberlite with the rock it intrudes and comprises non-kimberlitic clasts in a matrix of coherent kimberlite. A multi-stage emplacement process is invoked to account for the presence and the geometries of the Renard 4 rock units. Prior to the kimberlite eruption, coherent kimberlite dykes were emplaced. The eruption and filling of the diatreme were succeeded by emplacement of late-stage coherent kimberlite dykes and the emplacement of a late-stage volcaniclastic facies. Textures in the volcaniclastic facies as well as the juxtaposition of volcaniclastic, transitional and coherent rock types indicates that the present day surface of the Renard 4 kimberlite represents a level between the lower diatreme and the root zone of a Class 1 kimberlite pipe. It is proposed that concentration of country rock clasts occurred in areas of highest ascent velocity in the volcanic conduit. The presence of each of the Renard 4 rock types and their spatial distribution has important implications for the emplacement model of this kimberlite and provide important insight for general models pertaining to the formation of the root/diatreme transitional zone in other kimberlite pipes. The accretionary magmaclastic textures seen in some volcaniclastic rock types in Renard 4 indicates that fragmentation of the kimberlite magma occurs as deep as 2 kilometres below the earth surface and that during emplacement these magmas are inflated to many times the volume they currently occupy. It is furthermore suggested that the kimberlite magma is inflated, and the fragmental textures are formed in systems which may never have breached the surface.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.003 | 0.002 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.006 | 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".