Rock‐buffered versus fluid‐buffered geochemistry of structurally controlled, hydrothermal dolomite: Insights from the Sichuan Basin, China
Bibliographic record
Abstract
ABSTRACT Structurally controlled hydrothermal dolomitization, commonly driven by high‐pressure, high‐temperature fluid–rock reactions, offers insights into the tectonic evolution of sedimentary basins and the geochemical composition of their diagenetic fluids. Despite the numerous conceptual models that have been proposed to explain mechanisms of hydrothermal dolomitization, the behaviour of trace and rare earth elements in these reactions remains inadequately explored. To address such knowledge gaps, this study presents a detailed petrographical and geochemical analysis of the Longwangmiao Formation (Lower Cambrian) in the Sichuan Basin, China. Petrographical examinations revealed several generations of planar‐s, replacive dolomite (RD) and non‐planar, saddle dolomite (SD). RD1 (10 to 50 μm) and RD2 (50 to 120 μm) have similar geochemical signatures, which are indicative of a seawater‐derived diagenetic fluid in a shallow‐burial setting. These paragenetic stages denote the transition from an open, fluid‐buffered system during replacement dolomitization to a closed, rock‐buffered system during recrystallization. SD1 and SD2 are coarsely crystalline (0.3 to 5 mm), with high T h values (168 to 178°C), salinities and δ 18 O fluid values (4.9 to 7.4‰ VSMOW). SD1 and SD2 are also characterized by high 87 Sr/ 86 Sr and [Fe + Mn] values, but they have markedly different Eu/Eu* SN values (SD1 = 1.26 ± 0.22; SD2 = 0.68 ± 0.01). These results indicate that SD1 and SD2 precipitated in an intermediate‐ to deep‐burial setting from a mixture of seawater and hydrothermal fluids that had interacted with underlying siliciclastic or metamorphic basement rocks. These paragenetic stages precipitated in two different fluid‐buffered systems that likely correlate with distinct tectonic activities linked to the (i) Emeishan Large Igneous Province (Permian) and (ii) Longmenshan orogeny (Late Triassic). Our findings establish a genetic connection between basin‐scale tectonism and hydrothermal fluid flow that is recorded in the trace and rare earth element signature of dolomite, offering a framework to differentiate between rock‐buffered and fluid‐buffered geochemical signatures in structurally controlled settings worldwide.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".