| The mineralization of Black-rock-series has been focused by scholars at home and abroad.Recent years,Geologists have studied the mineralogical characteristics,occurrence forms,formation environment,metallogenetic epoch and metallogenetic mechanism of polymetallic minerals in the Black-rock-series at the bottom of Cambrian,and obtained a series of valuable achievements.However,the sequence of enrichment and mineralization of polymetallic elements at the bottom of Cambrian system and the correlation and division of the ore bed area have not been deeply studied.Meanwhile,the basic geological characteristics,mineralization material source,formation environment and genesis have been investigated in Cengong vanadium mining area.Study on the lithology and fabric characteristics of polymetallic key bed have gotted preliminary progress.However,the geochemical characteristics and relationship between the vanadium ore formation and siltstone of the key bed in the Cengong vanadium depposit is lacking.Based on the study of the Black-rock-series polymetallic ore and Cengong vanadium deposit at the Cambrian bottom in Guizhou,the metallogenic age,diagenetic metallogenic environment and geochemistry of barite,vanadium,nickel-molybdenum and phosphorus polymetallic layers at the bottom of Cambrian system were deeply discussed,and the metallogenic sequences of nickel-molybdenum,vanadium and phosphate were compared and analyzed.In the fine field measurement of the typical ore bearing profile of the largest Black-rock-series vanadium deposit in Cengong,a systematic study of petrology,mineralogy and elemental geochemistry has been carried.The relationship between the formation environment,genesis and key bed of the deposit and the mineralization of vanadium deposit in this area is discussed.Through the study,the following conclusions are drawn:(1)From lower to upper,the metallogenic process was divided into four sequences:phosphate,barite,vanadium and nickel-molybdenum mineralization sequences.(2)The light grey-green siltstone key bed,which distributes in the dark grey-black siliceous rocks and carbonaceous shales of the Sinian-Cambrian system Liuchapo formation and the first member of the Jiumenchong formation of the Cambrian is a direct indicator of vanadium ore prospecting.The mineral composition in key bed contain quartz,clay mineral,chlorite,pyrite,vanadium magnetite,barite,which have microscopic scale structure,layer and nodular structure.The key bed and the carbonaceous mudstone nearby enriched in V,Mo,Ni,Ba,P,Cr,Mg,Zn,K,Na,Al.(3)The ?Ce,Ceanom,and lithological characteristics in the light green siltstone layer and carbonaceous shales nearby,indicated an oxidative sedimentary environment in key bed,and a reductive to oxygen-poor environment the black shale,siliceous rock and limestone.(4)The enrichment of polymetallic elements,the diagram of Al2O3-SiO2,the diagram of w(REE)-w(La/Yb)N,and U/Th ratios indicate the progress of hot water and deep-source materials in the deposition.According to the characteristics of the strata geochemistry and mineralogy,establish the vanadium ore metallogenetic mechanism,in which metallogenic material is provided from sea bed,and siltstone riched in clay minerals,which is formed in oxidation environment,flow into the anoxic basin as clastic.The clastic flow carried oxygen to the bottom of sea,meanwhile,the mica,clay,magnetite mineral and organic matter in siltstone,reacted with V in seawater by metasomatism and adsorption,forming the vanadium deposit. |
PDF Full Text Request