Abstract:

Nephrite is an important mineral resource, and its geochemical characteristics are crucial for understanding the genesis of mineral deposits and assessing resource potential. This study investigates the basaltic rock-hosted nephrite from the Guizhou Luodian, Guangxi Dahua, and Guangxi Bama regions. Utilizing electron microprobe analysis and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), we systematically analyzed the major, trace, and rare earth element compositions of representative nephrite samples. The findings indicate that the primary chemical constituents of basaltic rock-hosted nephrite in the Qiangui region are SiO₂, CaO, and MgO, with average concentrations lower than the theoretical values for tremolite minerals. The SiO₂ content is found to be higher than that of ultramafic deposits, yet shows no significant difference when compared to neutral acidic nephrite, suggesting a relationship with silica supplied by surrounding rocks and late-stage hydrothermal fluids. Trace element analysis reveals pronounced positive anomalies for U, La, and Sm and a notable negative anomaly for Nb, while Ba exhibits no negative anomalies, providing a means to differentiate this nephrite from other genetic varieties. The rare earth element distribution patterns of Guizhou and Guangxi basaltic rock-hosted nephrite demonstrate significant similarity, with clear distinctions between light and heavy rare earth elements. Light rare earth elements are particularly enriched, and there are recognizable negative anomalies for Ce and Eu. Furthermore, the diabase associated with Guizhou and Guangxi nephrite shows strong affinity to Emeishan basalt, as reflected in their similar rare earth element distribution patterns. Finally, based on the variations in δCe, δEu, and ∑REE values among nephrite from different sources, effective differentiation can be achieved through dendrogram analysis.

Key words: nephrite, basaltic rock-hosted metasomatic deposit, major and trace element, rare earth element