Geology, U-Pb geochronology and stable isotope geochemistry of the Heihaibei gold deposit in the southern part of the Eastern Kunlun Orogenic Belt, China : A granitic intrusion-related gold deposit?

The Heihaibei gold deposit is a newly discovered gold deposit in the southern part of the Eastern Kunlun Orogenic Belt. Its most distinctive features are that the gold mineralization is hosted in monzogranite, and that the presence of pre-ore (possibly syn-ore) monzogranite and post-ore gabbro allows to constrain the minerali-zation's formation age. Zircons from the monzogranites yield U-Pb ages of 454 +/- 3 Ma, while zircons separated from the gabbro dikes cutting the monzogranites and gold mineralized body yield U-Pb ages of 439 +/- 3 Ma, which is interpreted to be the minimum age of the Au mineralizing event. Combined with the regional geological background, we proposed that the Heihaibei Au mineralization occurred during the subduction stage of the Early Paleozoic Proto-Tethys ocean. The ore assemblage is dominated by pyrite, arsenopyrite and native gold. The hydrothermal alteration that has led to the peculiar enrichment of Au is not systematically distributed and displays no clear concentric zoning pattern. The main mineralization formed during three stages: the K-feldspar-quartz-pyrite (Py1)-arsenopyrite-sericite-epidote stage (I), the quartz-pyrite (Py2)-native gold-chlorite stage (II), and the quartz-carbonate stage (III). The main gold mineralization occurred during stage II. Fluid inclusion homogenization temperature and salinities decrease from stage I (Th., 268-412 C; W., 6.87-16.63 wt% NaCl equiv.) to stage II (Th., 183-288 C; W., 3.69-14.84 wt% NaCl equiv.). The 818O and 8D values (818OH2O = 4.9 to 9.7%o; 8DV-SMOW =-84.1%o to -81.1%o) of quartz samples from stage I and stage II are comparable to a magmatic-hydrothermal ore-forming fluid that possibly underwent fluid-rock interaction with the Nachitai Group metamorphic rocks during the early ore-forming stage. The relatively uniform 834S values (834SV-CDT = 7.7 to 8.5%o) are slightly elevated compared to magmatic 834S values, but could be derived from a magma if a significant crustal melt component is present. Moreover, the 834S values are within the S isotopic composition range of a granitic reservoir, suggesting that they are probably inherited from the Heihaibei monzogranites. The Pb and Hf isotope compositions imply a close genetic association between the gold mineralization and granitic magmatism, which are both the products of the mixing of crustal and mantle sources. The trace element compositions of pyrite provide additional evidence that the gold mineralization in the Heihaibei deposit was related to the magmatism. Compared with the typical characteristics of orogenic gold and intrusion-related gold systems (IRGS) deposits, the Heihaibei gold deposit may instead be classified as a granitic intrusion-related gold deposit.Peer reviewe

Unleashing the Power and Energy of LiFePO₄‑Based Redox Flow Lithium Battery with a Bifunctional Redox Mediator

Redox flow batteries, despite great operation flexibility and scalability for large-scale energy storage, suffer from low energy density and relatively high cost as compared to the state-of-the-art Li-ion batteries. Here we report a redox flow lithium battery, which operates via the redox targeting reactions of LiFePO₄ with a bifunctional redox mediator, 2,3,5,6-tetramethyl-<i>p</i>-phenylenediamine, and presents superb energy density as the Li-ion battery and system flexibility as the redox flow battery. The battery has achieved a tank energy density as high as 1023 Wh/L, power density of 61 mW/cm², and voltage efficiency of 91%. Operando X-ray absorption near-edge structure measurements were conducted to monitor the evolution of LiFePO₄, which provides insightful information on the redox targeting process, critical to the device operation and optimization

Influence of Ionic Liquid on Recombination and Regeneration Kinetics in Dye-Sensitized Solar Cells

Nonvolatile electrolyte solutions are necessary for dye-sensitized solar cells (DSCs) with good long-term stability. Such electrolytes usually contain room-temperature ionic liquids (RTILs) and consequently possess higher viscosity and ionic strength than the volatile electrolytes used in current champion cells. In this study, we systematically investigated the effect of an RTIL additive on the performance of DSCs employing either a classical Ru-complex dye or a recently developed organic D-A-π-A dye, in combination with either I^–/I₃^– or [Co­(bpy)₃]^2+/3+ as redox mediator. Using impedance spectroscopy and transient absorption measurements under various background illumination intensities, recombination and regeneration kinetics were examined. Recombination is accelerated in the I^–/I₃^– devices upon addition of RTIL, regardless of the dye used, but it is retarded in the [Co­(bpy)₃]^2+/3+ devices. Addition of RTIL slowed regeneration in I^–/I₃^– devices for both sensitizers, marginally accelerated it for [Co­(bpy)₃]^2+/3+ with the Ru-complex dye, and did not significantly affect it for [Co­(bpy)₃]^2+/3+ with the D-A-π-A dye. We show that these findings cannot be explained by diffusion limitations caused by increased solution viscosity or by a shift in the TiO₂ conduction band relative to the electrolyte redox level. These findings should be useful for future optimization of RTIL-based DSCs

<i>N</i>‑Annulated Perylene-Based Push–Pull-Type Sensitizers

Alkoxy-wrapped <i>N</i>-annulated perylene (NP) was synthesized and used as a rigid and coplanar π-linker for three push–pull type metal-free sensitizers <b>QB1</b>–<b>QB3</b>. Their optical and electrochemical properties were tuned by varying the structure of acceptor. These new dyes were applied in Co­(II)/(III) based dye-sensitized solar cells, and power conversion efficiency up to 6.95% was achieved, indicating that NP could be used as a new building block for the design of high-performance sensitizers in the future