Metallogenetic Characteristics And Regularities Of Au-V Mineralization In Lower Cambrian Black Rock Series, Southern Qinling Moutain, China

One middle scale gold-vanadium deposits and another super-large scale vanadium deposit was hosted in black rock series in Shuigoukou Formation at the bottom of Cambrian in Southern Qinling Mountain,so the study of black rock and relevant deposits has very important significance of both prospecting practice and metallogenetic theory. Through field geological investigation together with lab testing,geological and geochemical characteristics of the black ore-bearing rock series,and especially the metallogenetic characteristics and regularities of gold-vanadium Mineralization in the black rock series were studied in the subject.The black rock series of Shuigoukou Formation in Southern Qinling occurs in the fault basin nearby a string of isolated paleo-uplifl,and consists of thin-interbed carbonaceous- pelitic-silicic slate.They are higher TOC content,lower dissolved hydrocarbons and hydrocarbons originated from kerogen cracking in black rock series. The features of Biomarkers indicate the organic matter has mainly come from marine microorganism and phycomycete.Biology and organic matter played an important role in concentration,migration and precipitation of the metallogenetic elements.The black rock series,enriched in Au,V,Mo,U elements and beneficial for ore forming,was hydrothermal sedimentary genesis→alternative sedimentary genesis between hydrotherm and normal condition→normal sedimentary genesis in the anoxic environment.Xiajiadian gold-vanadium deposit is a typical deposit hosted in the black rock series and controlled by the strata,favorable lithology and structure.The gold orebody is lenticular,platy-like.Gold occurs as independent mineral mainly in the inter grain of quartz and fracture.Wall-rock alteration is weak and the main alteration types in gold deposits are silicification and pyritization.The water mostly comes from strongly reconstructed meteoric water,according to the hydrogen and oxygen isotopes composition of inclusion of the mineralized quartz.On the basis of analysis PGE and Si isotopes,it is shown that the deposits probably come from many sources,but stratum is the main source. Metallogenetic characteristics indicate the ore deposit is alterative hydrothermal deposit. The vanadium orebodies,which have been controlled by the strata of black rock series,are simply layered.Ore grade and thickness are stable along strike and tread.There are 3 types of vanadium ore:①the argillaceous silicic slate -type,②the carbonaceous clay rock -type and③the carbonaceous silicic clay rock-type,usually the vanadium-rich one,all of the three types present mainly a structure of layered.Vanadium occurred as roscoelite,iron oxide and sefstromite etc.Sedimentary genesis is determined by the features and mineralization ways of the Vanadium deposit.Metallogenetic regularities of gold-vanadium mineralization hosted in black rock series:The black rock series originate from the fault basin and on the margin of isolated paleo-uplift,in which there were sufficient sedimentary substances of terrestrial sources and endogenous sources.The black rock series enriched in ore-forming elements,such as Au,V etc.,is not only ore source beds but also host ore beds.The interbeds of the carbonaceous silicic rock and carbonaceous clay slate with concretionary phosphate bed show the sedimentary environment of the interaction of the transgression and regression, which is favorable to vanadium ore-forming or preliminary gold enrichment and gold ore-forming by alteration in later period.The deference between the ore-forming way of the gold and that of vanadium is also revealed in this thesis.