Geochemical Characteristics of Muscovite and Feldspars in Pegmatites: Significance for Rare Metal Pegmatite Mineralization in the Duanfengshan Area, Hubei Province, South China

Abstract

The Duanfengshan deposit is a newly discovered large pegmatitic-type Nb-Ta deposit in the central section of the Jiangnan orogenic belt, South China. There are three types of pegmatite in the Duanfengshan area: microcline pegmatite, microcline-albite pegmatite and albite pegmatite. Although several geological, geochronological and geochemical studies of this deposit have been carried out, the relationships between the evolution degree of different types of pegmatites and mineralization are still unclear. We address this problem through systematic petrographic and geochemical studies of muscovite and feldspars from two representative pegmatite veins, the No. 328 microcline-albite pegmatite vein, and the No. 610 albite pegmatite vein. The results of electron probe microanalysis (EPMA) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of muscovite and K-feldspar reveal that K/Rb ratios decrease with increasing Rb, Cs, Ga, Nb and Ta contents alongside decreasing Ba and Sr contents, suggesting that magmatic differentiation played a dominant role in rare metal mineralization. A comparison of the analytical results of this study with those from rare metal pegmatites globally suggests that the No. 610 vein has a high mineralization potential, whereas the No. 328 vein has relatively low mineralization potential. The results from this study may be applied to the evaluation of mineralization potential for other pegmatite veins in the Duanfengshan area and other rare metal pegmatite fields with similar geological settings.

Keywords

Duanfengshan / rare-metal pegmatite / EPMA / LA-ICP-MS / magma differentiation and evolution

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2025 Geological Society of China