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.

本数据集提供了取自大同碱性玄武岩的自形橄榄石斑晶的高精度电子探针显微分析（electron probe microanalysis, EPMA）定量数据，分为两个互补子集（表S1与表S2），以完整捕捉矿物微区成分的变化特征。表S1聚焦于微区成分剖面数据，涵盖多颗橄榄石颗粒，旨在覆盖不同结晶阶段的宽泛成分梯度。与之相对，表S2仅针对单颗橄榄石颗粒，包含9条精心定位的剖面数据；每条剖面均标注了具体的微区位置（如树枝状原生枝、次生枝或贫磷区域）与对应的晶体学取向（{110}或{021}晶面），以追踪同一颗粒内的微尺度成分变化。
两类表格中的核心测量参数包括镁橄榄石含量（forsterite content, Fo，以摩尔百分比表示，计算公式为Mg/(Mg+Fe)×100）与五氧化二磷（phosphorus pentoxide, P₂O₅，重量百分比），同时附带2σ标准偏差误差。此类误差值通过对比同一微区的电子探针X射线面扫分析（用于大区域成分可视化）与单点分析（用于高精度点测量）结果的一致性得出，确保误差评估契合实际分析流程与数据可靠性。
值得注意的是，本数据集捕捉到橄榄石树枝状生长过程中，镁橄榄石含量与五氧化二磷含量之间的三种显著协变模式（耦合、解耦合与无相关性）；这些模式是区分生长主导型与扩散主导型矿物环带的关键依据。本数据集可直接用于验证岩浆结晶动力学模型，助力解释大陆板内玄武岩（如大同火山岩系）的演化历史，并为全球火成岩环境下的橄榄石成分特征跨研究提供基准参照。