Author(s)

PeiYuan Sun^*, JiaYun Zhou

Affiliation(s)

Chinese Academy of Geological Sciences, Chengdu 610041, Sichuan, China.

Corresponding Author

PeiYuan Sun

ABSTRACT

Ion-adsorption-type rare earth element (REE) deposits represent a dominant resource in China. In-depth research on these deposits is crucial for enhancing the security of China's critical metal resources. Laos, a key country along the "Belt and Road" initiative, is rich in mineral resources, with significant discoveries including iron, gold, copper, lead-zinc, bauxite, and potash. In recent years, Laos has made substantial progress in REE exploration, identifying numerous deposits with development potential, among which REEs constitute a vital component. This study focuses on the weathering crust profile and fresh biotite monzogranite from the Ban Nam Ao ion-adsorption-type REE deposit in Houaphanh Province, Laos. Whole-rock major and trace element analyses, mineral composition determinations, and zircon U-Pb geochronology were conducted to elucidate the geochemical characteristics of the parent rock, its mineralogical features, and the enrichment behavior of REEs within the weathering crust. The zircon U-Pb age of the biotite monzogranite is (246.5 ± 0.59) Ma. The Ban Nam Ao granite exhibits high SiO₂ (average 69.07%), Al₂O₃, and K₂O contents, with an average Rittmann index of 1.5, classifying it as a calc-alkaline magmatic rock. The biotite monzogranite is characterized by high total REE concentrations and abundant easily decomposable REE-bearing minerals, making it an excellent source for ion-adsorption-type REE mineralization. Within the weathering profile, REE concentrations are generally elevated from the topsoil to the completely weathered layer and semi-weathered layer, with the highest REE enrichment observed at the transition zone between the completely and semi-weathered layers.

KEYWORDS

Biotite monzogranite; Ion-adsorption-type REE deposit; Petrogenesis; Ban Nam Ao

CITE THIS PAPER

PeiYuan Sun, JiaYun Zhou. Mineralogical and geochemical characteristics of the biotite monzogranite and associated Ion-Adsorption rare earth element deposit at Ban Nam Ao, Houaphanh province, Laos. Academic Journal of Earth Sciences. 2025, 3(1): 19-26. DOI: https://doi.org/10.61784/ajes3011.

REFERENCES

[1] Dutta T, Kim K H, Uchimiya M, et al. Global demand for rare earth resources and strategies for green mining. Environmental Research, 2016, 150: 182-190.

[2] Roskill R E. Rare Earths and Yttrium: Market Outlook to 2015. London: Roskill Information Services Ltd, 2011.

[3] Gulley A L, Nassar N T, Xun S A. China, the United States, and competition for resources that enable emerging technologies. Proceedings of the National Academy of Sciences of the United States of America, 2018, 115: 4111-4115.

[4] Sláma J, Kosler J, Condon D J, et al. Plesovice zircon — A new natural reference material for U-Pb and Hf isotopic microanalysis. Chemical Geology, 2008, 249: 1-35.

[5] Fan P F. Accreted terranes and mineral deposits of Indochina. Journal of Asian Earth Sciences, 2000, 18: 343-350.

[6] Li M Y H, Zhou M F. The role of clay minerals in forming the regolith-hosted heavy rare earth element deposits. American Mineralogist, 2020, 105: 92-108.

[7] Li M Y H, Zhou M F, Williams-Jones A E. Controls on the dynamics of rare earth elements during sub-tropical hillslope processes and formation of regolith-hosted deposits. Economic Geology, 2020, 115.

[8] Anenburg M, Mavrogenes J A, Frigo C, Wall F. Rare earth element mobility in and around carbonatites controlled by sodium, potassium, and silica. Science Advances, 2020, 6(41).

[9] Lu Y Q, Wang R C, Lu X C, et al. Reprint of Genesis of halloysite from the weathering of muscovite: Insights from microscopic observations of a weathered granite in the Gaoling Area, Jingdezhen, China. Applied Clay Science, 2016, 119: 59-66.

[10] Wang D, Zhou M F. REE fractionation in alkaline rock weathering profiles. Chemical Geology, 2023, 632: 121234.

[11] Zhang Y, et al. Geochemistry of the Bayan Obo REE deposit: Implications for ore genesis. Ore Geology Reviews, 2018, 101: 1-15.

[12] Wang X C, et al. Metamorphism and tectonic evolution of the Bayan Obo Group, Inner Mongolia. Precambrian Research, 2020, 342: 105650.

[13] Chao E C T, et al. The origin of the Bayan Obo Fe-REE-Nb deposit: A review. Economic Geology, 2016, 111(6): 1279-1308.

[14] Liu Y, et al. Mineralogy and REE enrichment mechanisms in the Bayan Obo carbonatites. Lithos, 2021, 384-385: 105992.

[15] Yang K F, et al. Extreme LREE enrichment in alkaline rocks: Insights from the Bayan Obo deposit. Chemical Geology, 2022, 588: 120682.

[16] Deng X H. Hydrothermal alteration and REE remobilization in the Bayan Obo deposit: Evidence from in-situ mineral analysis. Geochimica et Cosmochimica Acta, 2023, 342: 78-95.

[17] Hoshino M, Sanematsu K, Watanabe Y. REE mineralogy and resources. Handbook on the Physics and Chemistry of Rare Earths, 2016, 49: 129-291.

[18] Ichimura K, Sanematsu K, Kon Y, Takagi T, Murakami T. REE redistributions during granite weathering: Implications for Ce anomaly as a proxy for paleoredox states. American Mineralogist, 2020, 105(6): 848-859.

[19] Farrah H, Pickering W F. pH effects in the adsorption of heavy-metal ions by clays. Chemical Geology, 1979, 25(4): 317-326.

[20] Ohta A, Kawabe I. REE(III) adsorption onto Mn dioxide (delta-MnO2) and Fe oxyhydroxide: Ce(III) oxidation by delta-MnO?. Geochimica et Cosmochimica Acta, 2001, 65(5): 695-703.

[21] Quinn K A, Byrne R H, Schijf J. Sorption of yttrium and rare earth elements by amorphous ferric hydroxide: Influence of pH and ionic strength. Marine Chemistry, 2006, 99(1-4): 128-150.