K isotopes reveal fluid exsolution and Li enrichment in the Koktokay No. 3 pegmatite dike
Year: 2026
Type: article
Abstract: Introduction: Lithium–cesium–tantalum pegmatites are critical sources of rare metals, yet the mechanisms of their formation, especially the role of fluids in elemental and isotopic fractionation, remain debated. Materials and methods: We investigated the Koktokay No. 3 pegmatite dike, the largest rare-element pegmatite in China, using K isotopes and chemical compositions of K-feldspar and muscovite across its concentric zones (I–VIII), combined with petrological modeling. Results: The results show a strong link between fluid exsolution, Li enrichment, and negative δ41K shift, corresponding to abrupt release of fluids and a rapid decline in solid phase abundance. Modeling indicates that low fluid–melt partition coefficients (Dfluid/melt = 0.1 for Li) best reproduce the observed Li enrichment, highlighting fluid exsolution as a key driver of rare-element accumulation. Conclusions: These results provide compelling evidence that late-stage fluid exsolution controls elemental enrichment and modulates K isotopic fractionation, offering new constraints on the petrogenesis of evolved pegmatite systems.
DOI: 10.20935/acadeps8254
Authors: Shan-Ke Liu, Ben-Xun Su, Wen-Jun Li, Dong-Mei Tang, Qi-Feng Zhou, Yang Bai, Ke-Zhang Qin, Ping Shen
Language: English
Subfield: Geophysics
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W7156226954