Dataset for Dendritic Growth Controls Forsterite-Phosphorus Coupling/Decoupling in Olivines: A Novel Proxy for Growth-Dominated Zoning

This dataset presents high-precision electron probe microanalysis (EPMA) quantitative data of euhedral olivine phenocrysts extracted from Datong alkaline basalts, structured into two complementary subsets (Table S1 and Table S2) to capture mineral microcompositional variations. Table S1 focuses on microzone compositional profile data, covering multiple olivine grains and targeting broad compositional gradients across different crystallization stages. Table S2, by contrast, is dedicated to a single olivine grain, containing data from 9 carefully positioned profiles—each annotated with specific location details (e.g., dendritic primary branches, secondary branches, or phosphorus-depleted regions) and corresponding crystallographic orientations ({110} or {021} faces) to track fine-scale compositional changes within the same grain.
Key measured parameters in both tables include forsterite content (Fo, expressed in mol%, calculated as Mg/(Mg+Fe)×100) and phosphorus pentoxide content (P₂O₅, in wt%), alongside 2σ standard deviation errors. These error values are derived from comparing the consistency of results between EPMA X-ray mapping (for large-area compositional visualization) and single-spot analysis (for high-precision point measurements) of the same microregions, ensuring the error assessment reflects the actual analytical workflow and data reliability.
Notably, the dataset captures three distinct covariation patterns between Fo and P₂O₅ (coupling, decoupling, and no correlation) that emerge during olivine dendritic growth—patterns critical for distinguishing growth-dominated versus diffusion-dominated mineral zoning. This data resource directly supports the validation of magmatic crystallization kinetic models, aids in interpreting the evolutionary history of continental intraplate basalts (like the Datong volcanic system), and provides a benchmark for cross-studies of olivine compositional signatures in global igneous settings.