Characterization of ‘CCMb’ calcite from Carrara marble as reference material for microanalysis
Bibliographic record
Abstract
We document the development of a calcite reference material intended primarily for in-situ oxygen-isotope microanalysis by secondary ion mass spectrometry (SIMS). The major, minor and trace element composition of this material (designated “CCMb”) was also characterized by microbeam techniques (EPMA, LA-ICP-MS) applied to polished grains embedded in epoxy mounts and by bulk-grain techniques involving acid-digestion and analysis by ICP-MS and ICP-OES. A 3-gram sub-sample was cut from a hand-sized piece of calcium carbonate marble weighing approx. 300 grams. The set of chemical and isotopic parameters evaluated here yielded an overall material profile that is consistent with the marbles quarried in the mountains above the town of Carrara in northern Italy. The sub-sample was crushed and sieved into a fine fraction consisting of all material that passed a 425 µm sieve and a coarse fraction of grains falling between 425 and 710 µm screens (the main fraction used for nearly all analyses; 0.982-gram total yield). Two polished epoxy mounts (1-inch / 25 mm diameter) were prepared for microanalysis; the first mount contained a set of 6 grains (‘Mount-4’), with 25 grains on the other (‘Mount-1’). Characterization by in-situ microbeam techniques included the following: 1) imaging of grains using back-scattered scanning electron microscopy (BSE-SEM) to check for absence of chemical zoning and of inclusions of other carbonates; 2) analysis of grains by EPMA to determine the concentration of the dominant mineral-forming cations Ca and Mg; 3) analysis of grains by LA-ICP-MS to determine the concentration and variance of common trace elements; 4) analysis of grains by SIMS to determine whether the oxygen-isotope composition (δ18O) is acceptably uniform for use as a microanalytical reference material. A common acceptance threshold in the literature is a δ18O variance near 0.3-0.5‰ at the 2 standard deviation level (e.g., Valley and Kita, 2009), where 0.3‰ is effectively the method background noise level driven by ion counting statistics and instrument stability. A small piece of this marble has been deposited in the Geostandards collections of the Museu de Geologia Valentí Masachs at the Universitat Politècnica de Catalunya. The reference of this speciment is GSTD0020.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".