Crustal evolution of alkali basalts: A case study of the Cenozoic Datong volcanoes, North China Craton

This dataset is used to study the crustal evolution of alkaline basalts from the Cenozoic volcanic group in Datong, Shanxi. The hypothesis is that the geochemical and mineralogical characteristics of these basalts provide crucial information on the differentiation and storage conditions of magma in the crust, revealing the magmatic evolution mechanisms during ascent and emplacement.
Data Collection Methods：
1.Point Counting Method: Modal mineral composition analysis of basalt thin sections was performed, providing quantitative data for olivine, clinopyroxene, plagioclase, and the matrix.
2.Electron Probe Microanalysis (EPMA): An electron probe was used to analyze the major elements of key mineral phases, including olivine, clinopyroxene, plagioclase, and the matrix. Probe conditions typically included an accelerating voltage of 15 kV and a beam current of 20 nA, ensuring precise measurements of mineral chemical compositions.
3.Whole-rock Major and Trace Element Analysis: Major elements were determined by X-ray fluorescence (XRF), and trace elements were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Standard and blank samples were used for calibration to ensure the accuracy of the data.
Key Findings：
1.Mineral Composition: The composition of olivine phenocrysts suggests fractional crystallization. The chemical composition of clinopyroxene indicates crystallization in evolved magmas. Compositional variations in plagioclase reflect dynamic conditions within the magma system. The presence of clinopyroxene-olivine-plagioclase glomerocrysts indicates magmatic mixing and storage processes.
2. Geochemical Trends: Whole-rock major element data reveal the alkaline nature of the basalts, while trace element data indicate significant magmatic differentiation. Differences in SiO2 and MgO content between Group 1 and Group 2 samples suggest varying degrees of magmatic evolution and storage depths.
3. Insights into Crustal Evolution: Mineral-melt equilibrium thermobarometry calculations show that Group 1 and 2 basalts crystallized in different magma chambers. Continuous magmatic replenishment may have driven the evolution of the volcanic conduit system, resulting in differing differentiation histories for the two groups.
These data help reconstruct the petrogenetic evolution of the Datong basalts, highlighting the role of fractional crystallization and magmatic replenishment within the crust, providing strong support for the evolution of alkaline basalts in the crust.
This dataset can be used for regional petrological comparisons, crustal evolution studies, and further crust-magma interaction modeling. Researchers should consider possible uncertainties in the analysis process and calibration standards to ensure accurate interpretation. This dataset provides significant support for volcanic petrology and regional crustal dynamics research.