Experimental and field investigations of serpentinization and rodingitization
Bibliographic record
Abstract
The chemical evolution of peridotites and felsic rocks included in or adjacent to them, and fluids during the hydrothermal alteration of these rocks is the subject of this study. Experiments using a flow-through hydrothermal apparatus, and studies of natural samples from the JM Asbestos chrysotile deposit in the Asbestos ophiolite, Quebec, were the means by which the various topics of this thesis were investigated. Open-system fluid-rock interaction was studied by flowing deionized water or a 0.1 m CaCl2 solution through olivine (Fo91) and lherzolite at a temperature of 300°C and a pressure of 300 bars. During these experiments, the original minerals (olivine, orthopyroxene and clinopyroxene) were altered to an assemblage, which consisted of serpentine-group minerals (conical, polygonal, and cylindrical fibers, and plates), brucite and magnetite. Reaction of lherzolite with deionized water and thermodynamic modelling indicate that the highest pH and calcium concentration are attained when pyroxenes are present in the unaltered rock, and that these parameters are at maximum in the presence of the buffering assemblage serpentine + brucite + diopside. Alteration of olivine by 0.1 m CaCl2 aqueous solution does not lead to the formation of secondary calcium phases. These results, supported by thermodynamic calculations, suggest that calcium-rich fluids can circulate through forsteritic olivine-rich lithologies without inducing calcium metasomatism. In the JM Asbestos mine, these Si-Al lithologies are largely felsic dykes, which, based on geological relationships, are interpreted to have been emplaced after serpentinization of the host peridotites began, but before obduction of the Asbestos ophiolite onto the Laurentian continental margin. Slates underlying and in thrust contact with serpentinite are also locally rodingitized. Mass balance calculations suggest that the calcium responsible for the rodingitization of the slates may have been derived locally, whereas the calcium responsible for the rodingitization of the felsic dykes was most probably derived from a source remote from the dykes. The strong dilution in rodingites and nephrites of the low-solubility minor and traces elements P, Cr and Zr suggests that very large amounts of fluids were involved in calc-silicate metasomatism of the felsic dykes and adjacent serpentinites. The absence of CO2 and presence of hydrocarbons (alkanes from methane to pentane) in the fluid inclusions of both episodes is an indication that the fluids responsible for calc-silicate alteration were derived from the serpentinites. (Abstract shortened by UMI.)
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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) | 0.001 | 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 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".