Geology and mineralization of the Dongping supergiant alkalic-hosted Au-Te deposit(>100 t Au)in Northern Hebei Province,China:A review

The Dongping deposit is the largest alkalic-hosted gold deposit in China containing>100 t of Au.This paper presents a new understanding for Dongping ore system,based on the previous studies.The mineralization originally occurred at 400-380 Ma,simultaneous with emplacement of the Shuiquangou alkaline complex,and was overprinted by the hydrothermal activity in the Yanshanian.Isotope compositions of ores indicate metals of the deposit are mainly provided by the Shuiquangou complex.Ore-forming fluids are characterized by increasing oxygen fugacity and decreasing sulfur fugacity,while tellurium fugacity increased in the Stage II-2 and decreased in Stage II-3.These systematic changes are closely related to the processes of mineral precipitation and fluid evolution.Sulfide precipitation from Stage Ⅰ to Stage Ⅱ was triggered by fluid boiling,which leads to the precipitation of Pb-Bi-Te,due to decrement of sulfur fugacity.Condensation of gas phase containing high concentration of H_2Te leads to precipitation of Te-Au-Ag minerals and native tellurium.Based on these hypotheses,this paper present a polyphase metallogenic model as follow.During the Devonian,fluids were released from alkaline magmas,which carried ore-forming materials form the surrounding rocks and precipitate the early ores.During the Jurassic-Cretaceous,fluorine-rich fluids exsolved from highly factionated Shangshuiquan granite,which extracted and concentrated Au from the Shuiquangou complex and the Sanggan Group metamorphic rocks,and finally formed the Dongping gold deposit.

Distribution and environmental impact factors of picophytoplankton in the East China Sea during spring

Marine picophytoplankton(Pico)as a major contributor to primary productivity in oligotrophic waters,play a very important role in marine material cycle and energy conversion,and their key role in the carbon cycle and global climate change is increasingly emphasized.To study the factors aff ecting the dynamic distribution of Synechococcus,Prochlorococcus,and picoeukaryotes in the East China Sea(ECS),a marginal sea of the Northwest Pacific,we investigated 27 stations in May 2017,and collected 148 samples of Pico and nutrients from the surface to the bottom.By means of flow cytometry,the abundance of Pico was measured,and then we estimated the carbon biomass and analyzed the distribution of Pico.Finally,combined with the ECS unique geographical situation and hydrological regime,we evaluated various factors aff ecting the Pico in the ECS.In Pico community,the picoeukaryotes cell abundance was between 0.49×10^(2)-1.44×10^(4) cells/mL.Prochlorococcus ranged from 1.36×10^(3)-3.47×10^(4) cells/mL and Synechococcus ranged from 0.69×10^(3)-1.15×105 cells/mL.Synechococcus was the most,both in abundance and in carbon biomass.Picoeukaryotes were the least in abundance,but has larger contribution to carbon biomass than Prochlorococcus.Water temperature,salinity,and stability of water column influenced Pico distribution.Picoeukaryotes were abundant in the shelf sea,whereas Synechococcus and Prochlorococcus were detected in the northeast of Taiwan,China.This study provided basic information for the study of Pico communities in the ECS and its adjacent marine ecosystem.

GEOCHEMISTRY STUDY OF GOLD SILVER DEPOSITS IN THE MIDDLE UPPER PROTEROZOIC SUBERATHEM IN SOUTHERN QINLING METALLOGENETIC ZONE

According to Ihe combinations of mctallogcnetic elements and minerals assemblages,the Au-Ag deposits in the Middle-Upper Proterozoic Suberathcm of the middle of northern margin of Yangtze Platform could be classified into four types,(l)Au-Ag-Pb-Zn type,(2)Au-Ag-Te type,(3)Au-quartz vein type,(4)Au-Ag-Pb-Zn-Ba type.The Yangpin formation and the upper Dangyuhe subformation,which belong to Wudangshan group,are regarded as favorable strata for Au-Ag mineralization by systematic assessments for Au-Ag bearing ability of the strata,as well as the felsic rocks of Bikou group.The mctallogcnetic physicochemical conditions and the stable isotopic compositions(S.Pb,H.O,C)have been studied in this paper.The sources of metallogenetic materials,origins of fluids and genesis of various deposits have also been studied.

Microheterogeneity of the Koupol Deposit Fahlores as a Reflection of Changing of Physicochemical Parameters of the Ore-Forming Solution

New data on a zonal structure of the Koupol deposit fahlores grains are given, and features of their chemism are shown. The fahlores chemical composition within the zones evolves from essentially arsenious （Fe-tennantite and Zn-tennantite）, through mixed fahlores （Zn-tennantitetetrahedrite arsenious and Zn-tennantite-tetrahedrite antimonous）, to essential antimonous （Ag-bearing Zn-tetrahedrite）. Varying chemical composition manifested as mineralogical-geochemical zonation of the fahlores grains is caused by changes of physicochemical conditions of the ore forming process during the time.