| Lietinggang iron polymetallic deposit is located in the northwest corner of Linzhou basin in Tibet, and it is governed by the Deqing village of the Duilongdeqing county.Tectonic location of this deposit belongs to the Gangdese back-arc fault zone.Moreover,Lietinggang deposit is a newly discovered skarn iron polymetallic deposit in Fe-Mo-Cu-Pb-Zn ore concentration area of Linzhou basin in recent years.The strata of Lietinggang deposit is relatively simple, which mainly includes lower Triassic Chaqupu Group(T1-2c) carbonate rocks and Quaternary(Q). Faults and fissures are the main important overall structure style of this deposit.There are many types of intrusive rocks,including porphyritic monzonite granite, porphyritic granodiorite, diorite porphyry and huang-amphibolite rock.The mineralization is closely related to porphyritic monzonite granite and porphyritic granodiorite. Lietinggang deposit consists of nine ore bodies that are very different in size,scale and ore-grade.The orebodies mainly are lenticular and irregular.The No.II orebody is the largest scale orebody of this deposit,which is mainly occurred in the contact-zone skarn of the granite and carbonate rocks.Combined with the field observations,a comprehensive study of indoor mineral chemical characteristics, we can conclude that the skarns of Lietinggang deposit are mainly calcareous skarns and formed mainly in calcareous system. Skarn mineral assemblages mainly are: garnet, amphibole, pyroxene, epidote, chlorite and tourmaline. Among them, the garnet primarily belongs to the andradite-grossular series(And18.37~99.95Gro0.03~79.05Ura+Pyr+Spe0.52~14.47); pyroxene diopside belongs to Ca-Fe diopside series(Di53.56~99.91Hd1.61~44.55Jo0.08~5.11);hornblende amphibole are mainly calcium, actinolite+small amount of iron magnesium hornblende; chlorite is mainly Fe-Mg chlorite. The mineral chemical characteristics of garnet and amphibole can indicate that this deposit is a polymetallic deposit, which is consistent with the geological facts. There are many types and species of metallic minerals, including magnetite, molybdenite, chalcopyrite, pyrite, galena, sphalerite, pyrrhotite, etc. Among them, magnetite is the most important industrial and genetic types of ores, which mainly include growth massive,disseminated and vein magnetite.Mineral chemical characteristics of magnetites and the discrimination diagrams can suggest that both three types of magnetite belong to the hydrothermal magnetite. Pyrite mainly includes the euhedral-shaped granular ordinary pyrite and concentric annular plastic pyrite.Based on the detailed field geological survey and laboratory microscope observation,Lietinggang deposit can be divided into two mineralization periods and five mineralization stages:the early stage of skarn rock+degenerate alteration stage(skarn period)+early stage of hydrothermal quartz-sulfide stage+carbonate phase(hydrothermal phase),different mineralization stage has different types of mineral assemblages.The skarn period of mineralization:garnet+amphibole+pyroxene+epidote +tourmaline+massive magnetite+molybdenite and so.The hydrothermal mineral assemblages are the chalcopyrite+pyrrhotite+pyrite+galena+sphalerite and other sulphides.With the ongoing process of mineralization, the evolution of skarn period? hydrothermal period(early skarn stage?carbonate phase),the temperature,oxygen fugacity and salinity of the ore-forming fluid continue to decrease.The physical and chemical conditions of ores is relatively oxidizing environment,and then gradually evolved into a relatively reducing environment,which provide favorable conditions for the various minerals. |
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