Wenlanzhangite–(Y) from the Yushui deposit, South China: A potential proxy for tracing the redox state of ore formation
Date
2024
Authors
Liu, P.
Li, G.
Sun, N.
Yao, W.
Yu, H.
Tian, Y.
Yang, W.
Zhao, F.
Cook, N.J.
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Advisors
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Journal article
Citation
American Mineralogist: an international journal of earth and planetary materials, 2024; 109(10):1738-1747
Statement of Responsibility
Peng Liu, Guowu Li, Ningyue Sun, Wei Yao, Hong Yu, Yongfei Tian, Wenqiang Yang, Fengshang Zhao, and Nigel J. Cook
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Abstract
Mineral phases in which vanadium (V) and heavy-rare-earth elements (HREEs) coexist are rarely documented. Here, we report a new V-HREE-bearing silicate mineral species, wenlanzhangite-(Y), which is a vanadiferous derivate of jingwenite-(Y) [Y2Al2V24+(SiO4)2O4(OH)4] coexisting with jingwenite-(Y) in bedded/massive ores at Yushui, South China. Wenlanzhangite-(Y) forms as a dark brown, 70–100 μm thick rim on a core domain of jingwenite-(Y), which occurs as 100–200 μm columnar crystals. The color, streak, luster, and hardness (Mohs) are dark brown, yellow-gray, vitreous, and ~4, respectively. Compared to jingwenite-(Y), wenlanzhangite-(Y) has higher vanadium and lower aluminum contents. Calculated on the basis of 8 cations, the empirical formula is (Y1.26Dy0.17Er0.11
Gd0.09Yb0.09Nd0.09Sm0.06Sc0.04Ho0.03Ce0.02Tb0.02Tm0.02Pr0.01)Σ2.00(V3+1.46Al0.54)Σ2.00V24+(SiO4)2O4(OH)4, which can be simplified to the ideal formula Y2V23+V24+(SiO4)2O4(OH)4.
Wenlanzhangite-(Y) is triclinic, with space group P1(#2), Z = 2, and unit-cell parameters a = 5.9632(7) Å, b = 9.599(1) Å, c = 9.9170(9) Å, α = 90.033(8)°, β = 98.595(2)°, γ = 90.003(9)°, and V = 561.28(10) ų. Wenlanzhangite-(Y) is approved by the International Mineralogical Association Commission on New Minerals, Nomenclature and Classification (IMA2022-142). The structure of wenlanzhangite-(Y) is composed of a-axis-oriented chains of [VO₆] octahedra consisting of edge-sharing octahedra linked by insular [SiO₄] tetrahedra, leaving open channels occupied by rare earth elements. Observed compositional variation and crystal structure demonstrate that V³⁺ can substitute for Al³⁺ in jingwenite-(Y), forming wenlanzhangite-(Y). The occurrence of wenlanzhangite-(Y) indicates a relatively more reducing hydrothermal environment, causing a reduction of V⁵⁺ in oxidized fluids to V³⁺ and thus represents a useful proxy for tracing the redox state of ore formation.
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