Cathodoluminescence features, trace elements, and oxygen isotopes of quartz in unidirectional solidification textures from the Sn-mineralized Heemskirk Granite, western Tasmania
Bibliographic record
Abstract
Distinctive quartz-rich unidirectional solidification textures (USTs) occur in apical carapaces of the Sn-mineralized Heemskirk Granite in western Tasmania (SE Australia). They are spatially associated with abundant tourmaline-filled orbicules and cavities that have been overprinted by widespread tourmaline-quartz veins. Multiple UST-quartz layers that are intercalated with aplitic layers, and can locally extend for hundreds of meters. Individual UST layers consist dominantly of hexagonal quartz (>95%) with minor K-feldspar, plagioclase, biotite, muscovite, and magnetite. Scanning electron microscope-cathodoluminescence (SEM-CL) reveals that the aplitic quartz is homogeneous and CL-bright with minor CL-dark patches. The bases of the UST quartz crystals are homogeneous and CL-bright with minor thin CL-dark fractures, whereas the trigonal apexes of the UST-quartz display CL-oscillatory growth zones. LA-ICP-MS analyses show that UST-quartz has lower Ti, Li, and Sn than aplitic quartz, but higher Al, Li, Na, K, Mn, Fe, Ge, Rb, and Cs concentrations. At a pressure of ca. 1.3 kbar, the Ti-in-quartz geothermometer yields temperatures of 545 40 and 580 20 C for the UST and aplitic quartz, respectively. The UST-quartz has higher Al/Ti values of 5.8 to 32, and Ge/Ti values of 0.02 to 0.16, than quartz phenocrysts in aplite layers, which is consistent with crystallization from a highly evolved fluid. The O-isotopic compositions (+5.1 to +10.2) of UST and aplitic quartz are consistent with magmatic source circulated by minor meteoric and/or formation waters. Magnetite crystals in USTs have low Cr, V, Ni, Co, Cr, Sc, and high Ti, Al, Mn, Sn, Ga contents, and are overgrown by chlorite. These minerals are interpreted to have formed at UST-melt interface where hydrothermal fluids reacted with igneous minerals. The results show that the UST layers in the Heemskirk Granite precipitated from magmatic-hydrothermal aqueous fluid exsolved from granitic melt during emplacement into the shallow crust (610 km). Such UST layers are characteristics of mineralized intrusions, and therefore provide significant indications for mineral exploration.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| 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".