Genesis of fahlore in the Tianbaoshan lead–zinc deposit, Sichuan Province, China: a scanning electron microscopy–energy dispersive spectroscopy study

The Tianbaoshan deposit, located in the southwestern part of the Yangtze Block, is a representative Pb–Zn deposit in the Sichuan–Yunnan–Guizhou Pb–Zn metallogenic province. The Pb–Zn orebodies are hosted in the upper Sinian Dengying Formation dolostone. The predominant minerals are sphalerite, galena, pyrite, chalcopyrite, quartz, and calcite with minor arsenopyrite,fahlore, and dolomite. The deposit is characterized by relatively strong Cu mineralization. However, the relationship between Pb–Zn and Cu mineralization is unknown. We analyzed the mineralogy and composition of fahlore, chalcopyrite, arsenopyrite, sphalerite, and galena using scanning electron microscopy–energy dispersive spectroscopy, with the aim of providing new evidence for the genesis of the Pb–Zn–(Cu) ore. The results show that the Cu ore in the deposit is dominated by chalcopyrite and fahlore, both of which formed before or during the Pb–Zn ore-forming stage. The fahlore showed dramatic compositional variation and was characterized by negative correlations between Ag and Cu, and between As and Sb,suggesting substitution of Ag for Cu, and that As and Sb substitute in the same site in the fahlore lattice. Based on backscattered electron images and composition, the fahlorewas divided into two types. Type I fahlore crystallized early and is characterized by enrichment of Cu and depletion in Ag and Sb. Type II fahlore formed after Type I, and is rich in Ag and poor in Cu and As. Moreover,galena and fahlore are the host minerals of Ag. The variation of valence state with As host mineral—from fahlore to arsenopyrite—indicates the metallogenic environment changed from relatively oxidizing to reducing with a high p H. In the light of Gibbs energies of reciprocal reactions and isotherms for cation exchange, the composition of the fahlore implies its ore-forming temperature was lower than220 °C, corresponding with typical Mississippi Valley-type(MVT) deposits. Based on the geologic character and geochemical data of this deposit, we suggest that the Tianbaoshan deposit belongs to the MVT deposit category.

Geological significance of nickeliferous minerals in the Fule Pb–Zn deposit, Yunnan Province, China

Abstract The Fule Pb-Zn deposit is located in the Sichuan-Yunnan-Guizhou Province, and it is an important and giant low temperature metallogenic domain in China. In our research area, the Pb-Zn deposits are mainly hosted in the Permian Yangxin Formation and are composed of dolostone and limestone. The distance between the ore bodies and the Permian Emeishan basalt ranged from 50 to 160 m. In this study, the nickel rich minerals, including vaesite, polydymite and millerite, were reported for the first time in the Fule deposit. These minerals occurred as xenomorphic mineral aggregate and were sporadically distributed in the sphalerite-galena-calcite vein, which is the main ore type in the deposit. Our study indicated that the paragenetic sequence of minerals in the Fule deposit is the following order： polydymite → vaesite → mil- lerite → sphalerite → galena → tetrahedrite （tennantite）. The geological occurrence characteristics of those nicke- liferous minerals suggested that the Permian Emeishan basalt is a possible barrier layer of Pb-Zn ore-forming fluid, and it is an important source for the Ni and part of the Cu in the deposit. The Sichuan-Yunnan-Guizhou Pb-Zn mineralization province is a world-class production base of Pb and Zn, in which the Permian Emeishan basalt and Pb- Zn deposits have uniformly spatial distribution, but the relationship of mineralization between them is still under debate. This report provides new evidence for understanding the relationship between Pb-Zn mineral- ization and Permian Emeishan basalt in the Sichuan- Yunnan-Guizhou Pb-Zn mineralization province.

A visualization pipeline for in vivo two-photon volumetric astrocytic calcium imaging

Astrocytes,the multi-functional glial cells with the most abundant population in the brain,integrate information across their territories to regulate neuronal synaptic and cerebrovascular activities.Astrocytic calcium(Ca^(2+))signaling is the major readout of cellular functional state of astrocytes.The conventional two-photon in vivo imaging usually focuses on a single horizontal focal plane to capture the astrocytic Ca^(2+)signals,which leaves>80%spatial information undetected.To fully probe the Ca^(2+)activity across the whole astrocytic territory,we developed a pipeline for imaging and visualizing volumetric astrocytic Ca^(2+)time-lapse images.With the pipeline,we discovered a new signal distribution pattern from three-dimensional(3D)astrocytic Ca^(2+)imaging data of mice under isoflurane anesthetic states.The tools developed in this study enable a better understanding of the spatiotemporal patterns of astrocytic activity in 3D space.

利用定量单病毒示踪技术探究SARS-CoV-2与细胞膜融合动态过程

Viral envelope fusion with the host plasma membrane(PM)for genome release is a hallmark step in the life cycle of many enveloped viruses.This process is regulated by a complex network of biomolecules on the PM,but robust tools to precisely elucidate the dynamic mechanisms of virus-PM fusion events are still lacking.Here,we developed a quantitative single-virus tracking approach based on highly efficient dual-color labelling of viruses and batch trajectory analysis to achieve the spatiotemporal quantification of fusion events.This approach allows us to comprehensively analyze the membrane fusion mechanism utilized by pseudotyped severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)at the singlevirus level and precisely elucidate how the relevant biomolecules synergistically regulate the fusion process.Our results revealed that SARS-CoV-2 may promote the formation of supersaturated clusters of cholesterol to facilitate the initiation of the membrane fusion process and accelerate the viral genome release.