Jingwenite-(Y) from the Yushui Cu deposit, South China: The first occurrence of a V-HREE-bearing silicate mineral

Abstract

Abstract Jingwenite-(Y), Y2Al2V24+(SiO4)O4(OH)4, the first V-HREE-bearing silicate mineral discovered in nature, is an abundant component of a sediment-hosted stratiform Cu (SSC) deposit, Yushui, South China. The mineral occurs in bedded/massive sulfide-bearing ore and is associated with bornite, chalcopyrite, galena, xenotime-(Y), nolanite, thortveitite, roscoelite, barite, and quartz. Optically, jingwenite-(Y) is biaxial (+), with α = 1.92(4), β = 1.95(2), γ = 1.99(3) (white light), and 2V (calculated) = 83°. The dispersion is medium with r < v, and the pleochroism is with X = light brown, Y = brown, Z = dark brown. The color, streak, luster, and hardness (Mohs) are light brown, yellowish gray, vitreous, and 4½–5, respectively. Jingwenite-(Y) is monoclinic, with space group I2/a, Z = 4, and unit-cell parameters a = 9.4821(2) Å, b = 5.8781(1) Å, c = 19.3987(4) Å, β = 90.165(2)°, and V = 1081.21(4) Å3. The structure of jingwenite-(Y) has chains of edge-sharing Al(V,Fe)-O octahedra and V(Ti)-O octahedra extending along the b-axis and linked by insular Si-O tetrahedra, leaving open channels occupied by HREEs. Jingwenite-(Y) is a new nesosilicate structural type. Sm-Nd dating and Nd isotope signatures of jingwenite-(Y) reveal an epigenetic origin and suggest that HREEs and V were added to the SSC system via leaching of abundant heavy minerals in the footwall red sandstone by oxidized basinal brines. The abundance of jingwenite-(Y) at Yushui indicates that it could potentially be a valuable resource for HREE and V. Moreover, HREE and V mineralization can also occur in the same sediment-hosted Cu mineral system.