^1,2,3,4Wei Wu, ^2,3,4Yigang Xu, ⁵Zhaofeng Zhang
Geochimica et Cosmochimica Acta (in Press) Link to Article [https://doi.org/10.1016/j.gca.2026.01.014]
¹School of Tourism and Geography, Shaoguan University, Shaoguan 512005 Guangdong, China
²State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 Guangdong, China
³Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), 511458 Guangdong, China
⁴School of Earth and Planetary Science, University of Chinese Academy of Sciences, Beijing 100049, China
⁵Research Center for Planetary Science, College of Geosciences, Chengdu University of Technology, Chengdu 610059 Sichuan, China
Copyright Elsevier

To constrain calcium isotopic fractionation during magma differentiation and its significance for planetary geochemistry, this study analyzed δ44/40Ca compositions of whole rocks, clinopyroxene, and plagioclase in mafic–ultramafic intrusions from two major large igneous provinces: the Tarim Large Igneous Province (Xiaohaizi intrusion) and the Emeishan Large Igneous Province (Panzhihua intrusion). Whole-rock δ44/40Ca ranges from 0.75 to 1.00 ‰ for Xiaohaizi and 0.82 to 0.97 ‰ for Panzhihua, while Pl δ44/40Ca varies from 0.69 to 1.07 ‰ (Xiaohaizi) and 0.78 to 0.99 ‰ (Panzhihua). Disequilibrium in selected samples is attributed to distinct geological processes: magma replenishment (Panzhihua) and crustal material assimilation (Xiaohaizi). For equilibrium samples, the Ca isotopic fractionation factor between Pl and melt (1000lnαPl-melt) exhibits no correlation with Pl An content and remains stable under specific temperature–pressure conditions for mafic to ultramafic plagioclase. By integrating this new dataset with published Δ44/40CaCpx-Pl data (including ab initio predictions and magmatic evolution model results), we determined 1000lnαPl-melt at 1273 K is −0.07 ± 0.10 ‰ (2SD, N = 28). This study clarifies the role of Pl in magmatic Ca isotopic fractionation, providing a reliable framework for tracing magma evolution and reconstructing early crust formation processes of terrestrial planets.