Metal transport by oil: Application to ore genesis
Bibliographic record
Abstract
This thesis describes the results of an experimental study designed to measure and interpret the solubility of palladium oxide in crude oil, and the modification of a method for analyzing metal concentrations in crude oils. An approach that has been employed previously in the analysis of crude oils is to combust (dry ash) them and then leach the residues with acids to prepare an aqueous solution that can be analysed instrumentally. This method of preparation, however, has been criticized as being inaccurate because it led to underestimates of the metal contents of crude oil standards to which it was applied. In this study, modifications were introduced that now permit its reliable application. The modifications involved the use of PyrexTM tubes instead of platinum crucibles and addition of nitric acid and hydrogen peroxide to ensure that any residues remaining after dry ashing were completely oxidized. This modified method was tested by analyzing the nickel and vanadium concentrations of certified crude oil standards using this dry-wet-ashing preparation, leaching the residues with concentrated HCl, diluting them in Milli-Q™ water and measuring the concentrations of Ni, V in the resulting solutions using ICP-MS. The results show that the concentrations of the standards can be reproduced to ± 5% for concentrations ≥ 100 ppm and ± 10 for concentrations down to 1 ppm Ni or V. These results are similar to or better than those using other more costly or less accessible methods of analysis. This suggests, that at least for Ni and V, and probably for most other metals, concentrations of metals in crude oils can be analyzed reliably using the modified dry ashing – ICP-MS method described in this thesis. The solubility of palladium oxide was measured in three crude oils at temperatures of 150, 200 and 250 °C for a duration of seven days, which was shown by kinetic experiments to be sufficient to ensure equilibrium. The selected crude oils varied appreciably in their asphaltene, nitrogen and sulfur contents. Palladium concentration in the lightest crude oil (lowest asphaltene content) decreased systematically from 141 ± 34 ppb to 77 ± 17 ppb between 150 and 250 °C whereas in the other two crude oils, it reached a maximum at 200 °C. The concentration was highest in the heaviest crude oil, reaching 1183 ppb at 200 °C. This suggests that palladium can be dissolved in appreciable concentrations in liquid hydrocarbons and that its solubility is controlled by the proportion of asphaltene macromolecules. The concentration of palladium also increases with increasing nitrogen content and decreasing acidity, suggesting, as has been demonstrated for Ni and V, that it may be dissolved as porphyrin species, which are known to concentrate in the asphaltene fraction. The results of this study show that liquid hydrocarbons have the potential to transport palladium in amounts sufficient to form ore deposits, and emphasize the need for studies of environments in which palladium and hydrocarbons have been shown to be spatially associated.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".