Study On Occurrence State And Enrichment Mechanism Of Associated Cobalt In Han-Xing Type Iron Deposit

Han-Xing area is located in the central part of North China Craton,the south segment of Taihang Mountain,which is the famous for Han-Xing type rich-iron deposits in China.The main industrial ore in the area is magnetite.There is a large amount of Co in the magnetite,and the Co element in the ore reaches the standard of associated utilization,but the occurrence state of Co in the ore has not been figured out.Whether there are independent minerals of Co has not been determined,and its enrichment mechanism has not been clarified.In order to study the occurrence state and enrichment mechanism of Co in the magnetite of Han-Xing area,the ore samples collected in the field in various mining areas of Han-Xing were studied by petrography.Themorphological characteristics,structure and structural characteristics of the ore and the minerals symbiosis and associated relationshipswere found out.By means of XRD powder diffraction,electron probe analysis of metal minerals and element composition mapping of major and trace elements,the chemical composition of cobalt-rich metal minerals was ascertained and the independent mineral of cobalt element in Han-Xing area was determined as cobaltite.The occurrence state and enrichment mechanism of Co in Han-Xing area are figured out,which can provide some reference for the recovery and utilization of key metal cobalt in the area.The main metal minerals in magnetite in Han-Xing area were systematically studied,and the major accomplishments are as follows:1)The ore structures in Han-Xing area include massive structure,disseminated structure,breccia structure and banded structure,among which massive structure is the most developed.The ore textures are:(1)The crystalline texture is the most developed,including euhedral-granular texture,subhedral granular texture and allotriomorphic granular texture;(2)the disseminated texture and reaction rim texture formed by metasomatism;(3)the solid solution separation texture.2)The main metal mineral in the area is magnetite and the main metal sulfide is pyrite.In addition,there are chalcopyrite,chalcoite,pyrrhotite,hematite,goethite,cobaltite and other metal minerals;non-metallic minerals are tremolite,diopside,garnet,phlogopite,calcite,dolomite,serpentine.3)The main cobalt-containing mineral in the Han-Xing area is cobaltite,which was formed by the late magmatic hydrothermal mineralization after pyrite crystallization and occurs as by the veinlets or allotriomorphic granular taxturesmetasomatizing pyrite,as observed by the microscope and BSE images.Secondly,the pyrite is the metal sulfide mineral with the highest Co content,and Co element mainly enters the mineral lattice instead of Fe element in metal minerals in the form of Isomorphism.4)Combining the cobalt element geochemical characteristics with the geological background of Baijian mining area,we consider the Co element enrichment in Baijian mining is due to the magmatic activities,basic magma mixing many times with the acidic magma brought Co elements,and constantly in the process of magmatic-hydrothermal migration,carbonate components in the surrounding rock are assimilated continuously,which provides the basis for Co migration.With the change of pressure,temperature,oxygen fugacity and other physical and chemical conditions,Co is finally precipitated and enriched.