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[Ag6]4+ clusters are extremely rare in nature (only found in Ag-rich tetrahedrite group minerals). Due to their remarkable structures and some promising applications, a few synthesis phases that contain octahedral [Ag6]4+ clusters have been reported. However, the kinds of natural conditions that promote the formation of subvalent hexasilver clusters in tetrahedrite group minerals are still unclear. Kenorozhdestvenskayaite-(Fe), ideally Ag6(Ag4Fe2)Sb4S12□ is a new tetrahedrite group mineral containing a natural [Ag6]4+ cluster, found in the Yindongpo gold deposit, Weishancheng ore field, Henan Province, China. This new species occurs at the edges of galena crystals as anhedral grains of 2 to 20 μm in size and is associated with pyrargyrite, pyrrhotite, and siderite. Kenorozhdestvenskayaite-(Fe) is black in color with metallic luster. It is brittle with conchoidal fracture and has a calculated density of 5.329 g/cm3. The empirical formula calculated on the basis of cation = 16 apfu is M(2)Ag6M(1)(Ag2.41Cu1.20Fe1.84Zn0.71)Σ6.16X(3)(Sb3.82As0.01)Σ3.83S(1)S11.60S(2)□. It is cubic, with space group I 4 3m, a = 10.7119(6) Å, V = 1229.1(2) Å3, and Z = 2. Since kenorozhdestvenskayaite-(Fe) is a new tetrahedrite group mineral containing a natural [Ag6]4+ cluster, its structure is comparable to the synthetic ternary phosphide (Ag6M4P12) M 6 ′ . The presence of the unusual mineral assemblages, i.e., pyrrhotite and pyrargyrite, as well as the other keno-end-member tetrahedrites, indicates a low-fS2 state for the mineralization stage, probably a result of the fluid boiling process in an open system that likely contributed to the formation of S-deficient tetrahedrites. [ABSTRACT FROM AUTHOR]

The new mineral kenoargentotetrahedrite-(Zn), [Ag 6 ] 4+ (Cu 4 Zn 2) Sb 4 S 12□ , was discovered at the Yindongpo Au deposit, Henan Province, China. It occurs as black metallic anhedral grains or equant crystals up to 40 µ m in size. It is opaque in transmitted light and shows a greenish-grey colour in reflected light. Electron microprobe analysis for the studied material gave the empirical formula (on the basis of total cations being equal to 16 atoms per formula unit, apfu): M(2) (Ag 3.75 Cu 2.25) Σ6 M(1) [Cu 3.90 (Zn 1.18 Fe 0.69 Cd 0.26) Σ2.13 ] Σ6.03 X(3) (Sb 3.69 As 0.27) Σ3.96 S(1) S 11.94 S(2)□. Kenoargentotetrahedrite-(Zn) is cubic, I4‾ 3 m (no. 217), with a = 10.4624(4) Å, V= 1145.23(13) Å 3 , and Z= 2. The crystal structure has been refined to a final value of R1= 0.0247 on the basis of 274 independent reflections (Fo > 4 σ (Fo)) by using single-crystal X-ray diffraction data. The seven strongest X-ray powder diffraction lines (d in Å (I) (hkl)) are the following: 3.010 (100) (222), 1.844 (30) (044), 2.606 (22) (004), 1.572 (15) (226), 2.046 (9) (134), 7.35 (6) (011), and 1.909 (5) (125). Kenoargentotetrahedrite-(Zn) is isostructural with other keno-member tetrahedrites with the [Ag 6 ] 4+ cluster. The structure refinement result confirms the coupling between the site occupancy factor of subvalent hexasilver clusters at the M (2) site and that of the vacancy at the S (2) site. This relationship further substantiates the charge balance substitution mechanism of S-deficiency tetrahedrites: 6 M(2) Ag ++S(2) S 2-= M(2) [Ag 6 ] 4++S(2)□. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Bastnäsite-(Ce) and zircon from the Taipingzhen REE deposit have U-Pb ages of ∼408 Ma. • Partial melting of the lower crustal rocks provided the metallogenic materials. • Late Paleozoic large-scale U-REE mineralization occurred in North Qinling Orogen. Abstract The Taipingzhen deposit is a newly discovered REE deposit in the North Qinling Orogen (NQO), Central China. The REE ores are hosted in the altered fracture zones of Paleozoic strata and a granitic intrusion. The ore minerals mainly include bastnäsite-(Ce)[(Ce(CO 3)F], parisite-(Ce)[CaCe 2 (CO 3) 3 F 2 ], and synchysite-(Ce)[CaCe(CO 3) 2 F], and this deposit also contains some uncommon minerals, such as törnebohmite-(Ce)[Ce 2 Al(SiO 4) 2 (OH)], gatelite-(Ce) [CaCe 3 AlAl 2 Mg(Si 2 O 7)(SiO 4) 3 O(OH) 2 ], fluocerite-(La)[LaF 3 ] and F-rich cerite-(Ce)[(Ce,Ca) 9 Mg(SiO 4) 3 [SiO 3 (OH)] 4 F 3 ], which are identified here for the first time in China. To determine the timing of REE mineralization and explore possible genetic relationships between mineralization and granitic magmatism, the U-Pb ages of bastnäsite-(Ce) from ore and zircon from ore-hosting granite are obtained. The in situ LA-MC-ICP-MS U-Pb age of the bastnäsite-(Ce) provides a reliable 238U/206Pb-207Pb/206Pb lower intersection point age of 409 ± 16 Ma, and ID-TIMS analyses yield an U-Pb age of 407.8 ± 3.3 Ma; the U-Pb dating of the magmatic zircon reveals that the wall rock was emplaced at 457.1 ± 4.9 Ma, and the hydrothermal zircon age of 399.4 ± 3.5 Ma records the time of hydrothermal alteration, thus indicating that the REE mineralization in the Taipingzhen deposit occurred at approximately 409–400 Ma. This age coincides well with the U-Pb ages of the bastnäsite-(Ce) and zircon, revealing a genetic association between the hydrothermal fluid and the REE mineralization. The Hf isotopic compositions imply that the partial melting of Paleoproterozoic HP and UHP eclogite from the lower crust provided ore materials for the mineralization, and the deposit was generated in a retrograde metamorphic setting during the late Paleozoic postcollisional extension event in the NQO. Furthermore, combined with the geochronological data published for other U-REE metallic deposits in the NQO, our study indicates that the late Silurian-early Devonian granite-related U-REE metallic mineralization throughout the NQO mainly occurred during 421–395 Ma. [ABSTRACT FROM AUTHOR]

In Northern China, sandstone-type uranium (U) deposits are mostly developed in Mesozoic-Cenozoic basins. These U deposits are usually hosted in unvarying horizons within the basins and exhibit typical U-forming sedimentary associations, which is referred to as U-bearing rock series. This study describes the structural features of U-bearing rock series within the main Mesozoic-Cenozoic U-producing continental basins in Kazakhstan, Uzbekistan, and Russia in the western segment of the Central Asian Metallogenic Belt (CAMB), and Northern China in the eastern segment of the CAMB. We analyze the basic structural conditions and sedimentary environments of U-bearing rock series in Northern China and classify their structural styles in typical basins into river valley, basin margin, and intrabasin uplift margin types. The intrabasin uplift margin structural style proposed in this study can be used to indicate directions for the exploration of sandstone-type U deposits hosted in the center of a basin. At the same time, the study of structural style provides a new idea for exploring sandstone-type U deposits in Mesozoic-Cenozoic basins and it is of great significance to prospecting of sandstone-type uranium deposits. [ABSTRACT FROM AUTHOR]

A new mineral species of the mica group, fluorluanshiweiite, ideally KLiAl1.5□0.5(Si3.5Al0.5)O10F2, has been found in the Nanyangshan LCT (Li, Cs, Ta) pegmatite deposit in North Qinling Orogen (NQO), central China. Fluorluanshiweiite can be regarded as the F-dominant analogue at the A site of luanshiweiite or the K-dominant analogue at the I site of voloshinite. It appears mostly in cookeite as a flaky residue, replaced by Cs-rich mica, or in the form of scale aggregates. Most individual grains are <1 mm in size, with the largest being ca. 1 cm, and the periphery is replaced by cookeite. No twinning is observed. The mineral is silvery white as a hand specimen, and in a thin section, it appears grayish-white to colorless, transparent with white streaks, with vitreous luster and pearliness on cleavage faces. It is flexible with micaceous fracture; the Mohs hardness is approximately 3; the cleavage is perfect on {001}; and no parting is observed. The measured and calculated densities are 2.94(3) and 2.898 g/cm3, respectively. Optically, fluorluanshiweiite is biaxial (–), with α = 1.554(1), β = 1.581(1), γ = 1.583(1) (white light), 2V(meas.) = 25° to 35°, 2V(calc.) = 30.05°. The calculated compatibility index based on the empirical formula is −0.014 (superior). An electron microprobe analysis yields the empirical formula calculated based on 10 O atoms and 2 additional anions of (K0.85Rb0.12Cs0.02Na0.03)Σ1.02[Li1.05Al1.44(□0.47Fe0.01Mn0.02)Σ0.5] Σ2.99(Si3.55Al0.45) Σ4O10F2, which can be simplified to KLiAl1.5□0.5(Si3.5Al0.5)O10F2. Fluorluanshiweiite is monoclinic with the space group C2/m and unit cell parameters a = 5.2030(5), b = 8.9894(6), c = 10.1253(9) Å, β = 100.68(1)°, and V = 465.37(7) Å3. The strongest eight lines in the X-ray diffraction data are [d in Å(I)(hkl)]: 8.427(25) (001), 4.519(57) (020), 4.121(25) (021), 3.628(61) (1 12), 3.350(60) (022), 3.091(46) (112), 2.586(100) (1 30), and 1.506(45) (312). [ABSTRACT FROM AUTHOR]