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August 19, 2025Open Access

Petrographic, Geochemical, and Geochronological Characteristics of the Granite in Yunnan and Its Constraints on Ion-Adsorption Rare Earth Element Mineralization

Key Points

Mineralized granites contain significantly higher total REE concentrations compared to non-mineralized granites, revealing their potential for economic extraction.
Detailed analysis showed two main periods for iREE-host granites: Early Cretaceous and Paleocene–Eocene, indicating diverse geological history.
Integration of petrology features and zircon U-Pb dating provides a systematic understanding of the Tuguanzhai granite's mineralization process.
The discovery of abundant easily leachable minerals suggests new avenues for exploring iREE mineralization, highlighting innovation in methodology.

Abstract

The TuguanZhai rare earth deposit in Tengchong, along with the Longan and Yingpanshan deposits in Longchuan, is a significant ion-adsorption type rare earth (iREE) deposit in Yunnan, China. Previous studies mainly focused on the geochemistry of residual regolith or the migration and enrichment mechanism of rare earth elements (REEs), but lacked systematic analysis of the protoliths. To constrain this deposit and its protolith rock, called Tuguanzhai granite, we systematically integrate petrology features, petrogeochemistry, zircon U-Pb date, and artificial heavy mineral separation (AHMS). Specifically, iREE-host granites include two main periods in this area: the Early Cretaceous (112.13 ± 0.75 Ma) and the Paleocene–Eocene (52.78 ± 0.28 Ma, 48.56 ± 0.19 Ma). The former includes three types of biotite monzogranite with different grain sizes, and the latter is mainly medium-grained biotite monzogranite with local mylonitization. Geochemical features show that these granites generally share high alkalinity compositions (w(K2O + Na2O): 7.15 to 12.75 wt%) and potassium contents (w(K2O): 3.89 to 8.36 wt%). The mineralized granites exhibit significantly higher concentrations of the total REEs than non-mineralized granites, along with a strong enrichment of light REEs. Moreover, the results of AHMS reveal that the REE contents of apatite, allanite, and titanite in mineralized granites are 4.98, 1.29, and 1.90 times more abundant than in non-mineralized granites, respectively. Due to REEs being released from these REE-rich minerals in humid environments, there exists significant potential for iREE formation and exploration in the Early Cretaceous granites in western Yunnan. We innovatively propose the “abundance of easily leachable minerals” as a key indicator for iREE mineralization and exploration, having found it to be better than the traditional total REE contents.

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Zhang et al. (Tue,) studied this question.

synapsesocial.com/papers/68af494dad7bf08b1ead4ead https://doi.org/https://doi.org/10.3390/min15080872

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