Oscillatory Zoned Liddicoatite from Anjanabonoina, Central Madagascar. III. Trace Elements
Bibliographic record
Abstract
Abstract Large crystals of liddicoatite (tourmaline) from the Anjanabonoina Pegmatite of Central Madagascar are well-known for their distinct patterns of oscillatory zoning. This study follows two previous investigations, in which the crystal chemistry (Lussier et al. 2011a) and variations of major chemical constituents (Lussier & Hawthorne 2011) were characterized in detail. Here, the variations of elements present only at the trace level are investigated. The measurement by laser ablation inductively coupled plasma mass spectrometry of 26 trace elements, with abundances spanning four orders of magnitude (∼10−1 to 103 ppm) is reported. Trace elements were analyzed along continuous analytical traverses from the core to the rim of the crystal. Abundance profiles for most of the trace elements quantified (21 of 26) show clear oscillations that coincide with optical oscillatory zoning features. Throughout the crystal, the occurrence of compositional oscillation is independent of trace-element abundance; even where mean abundance is low, ∼1 ppm (e.g., V3+, Y3+, Th4+), oscillatory behavior is clear. Conversely, the magnitude of the oscillatory amplitude shows a strong near-linear dependence on element abundance. Within individual oscillatory zones, four unique line-shapes are observed, each differentiated by (1) the direction of a compositional discontinuity at the zone limits and (2) the orientation of the nonlinear curvature across the zone. For any individual zone, the variation in element concentration, C, can be fitted to the equation C = ±Aeλ(x−Φ)+ Δ where A is the zone amplitude; Φ is a reference position, and λi and Δi are fitted parameters. Comparison of the fitted equations shows that linear correlation between element pairs is common, occurring between pairs consisting of trace–trace, trace–major, and major–major elements. The oscillatory behavior of constituent elements is related to the location of the trace element in the tourmaline structure, with elements at the X- and Y-sites typically showing increases and decreases in abundance over single oscillatory zones. Throughout each zone, Mg has high abundance (∼104 ppm) at the start of each zone, followed by an extremely abrupt decrease in abundance, typically over a distance of <1 mm, making its behavior different to that of other elements (both trace and major). Finally, there are systematic differences in trace-element abundances between pyramid {201} and prism {100} sectors of the crystal, echoing the differences observed for major elements between these two sectors and consistent with face-dependent differences in element uptake.
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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".