The Study On Geological Characteristics Of Lietinggang Iron Polymetallic Deposit, Tibet And Metallogenic Regularity Of Typical Deposits In The North Gangdese Metllogenic Belt

Lietinggang is in the north of Gandise-Nyainqentanglha magmatic arc. It is related to Paleocene-Eocene intermediate-felsic volcanic rock, and Gandise-Nyainqentanglha magmatic arc is the vital area of Metallogenic prospect areas. In this paper, based on iron polymetallic deposit of Lietinggang, the author research on deposit geology, geochemistry, metallogenic chronology and optimized technology methods to analyze metallogenic characteristics of the iron polymetallic deposits on the northern edge of Gangdese Metllogenic Belt, including Leqingla, Xingaguo, Jialapu. It summarize the metallogenic regularity of iron polymetallic deposits in the northern margin to improve metallogenic sub series and point out the regional prospecting direction.Based on Lietinggang’s geological investigation, drilling core, Optical film and flake identification, it systematically study on orebody characteristics, ore fabric, wallrock alteration and the vein types. Lietinggang deposit is divided the metallogenic stage and mineralization stage. Combined with the geological fact and geochemical analysis, potential fact, it judged the metallogenic potential of skarn iron orebody and porphyry copper, molybdenum orebody.Diagenetic geochronology show that granodiorite formed in 58.69 Ma, and granite porphyry formed in 60.69 Ma. Re-Os isotopic dating of Molybdenite determined that metallogenic epoch is about 62 Ma, which formed in the Paleocene. Geochemical characteristics of magmatic rocks shows that the rock forming material source area, in addition to a large amount of mantle derived mass, shell source material was added. The deposit formed in the environment of the India Asia continental collision.Geochemistry Reserch of isotope and fluid inclusions show that the stable fluid of main metallogenic stage is the mantle derived magma. A small amount of fluid in the crust source is mineralized. Late mineralization process, atmospheric precipitation is added. Ore-forming process experienced magmatic exsolution volatile, fluid, supercritical fluid and the fluid mixing process. The source of iron(copper, molybdenum) orebody is mainly from mantle, but crust is added into the source. On the basis of the above study, author establish the matallogenic model of Lietinggang.In the paper, the Gangdese Nyainqentanglha magmatic arc identify the mineralization of the Paleocene. It preliminarily summarize the types of iron polymetallicdeposits and tease out 4 different types of deposits in Gangdese Nyainqentanglha magmatic arc, which is the skarn Pb-Zn deposits, the skarn iron Polymetallic deposits, the porphyry Mo deposits and cryptoexplosive breccia type and skarn type Pb-Zn(Ag) deposits. It is the temporal and spatial distribution of the typical deposit framework. At last, author discusses its Metallogenic Geodynamic background. Hf isotopic geochemistry of the metallogenic rock and Pb isotope of ore sulfides systematically expounds coupling relationship of the typical deposits in the north Gangdese.The innovations of this paper:1.The study on the geological characteristics of the Lietinggang, author put forward a new understanding that is skarn iron orebody and porphyry copper, molybdenum ore body. It is quite different from the other typical copper, molybdenum deposit in the Gangdese metallogenic belt, such as the Jiama, Qulong and Bangpu, as well as the typical Pb-Zn deposits, such as Yaguila, Dongzhongla. 2. Based on the study of metallogenic regularity in the north of the Gangdise, typical deposits is divided into skarn iron polymetallic deposits, skarn Pb-Zn deposits, porphyry molybdenum deposits and cryptoexplosive breccia type and skarn type Pb-Zn(Ag) deposits. It conclude and analogy 4 different types of deposits in geological characteristics, metallogenic background, material source and the temporal and spatial distribution. Author consider that high emplacement with acidic magma, slow cooling, crystallization in magma, and carbonate formation contamination in the skarn iron polymetallic deposit(Lietinggang, Jialapu) and cryptoexplosion breccia type and skarn Pb-Zn(Ag) deposits(Naronsongduo). But the metallogenic specialization in the skarn Pb-Zn deposit(Yaguila, Dongzhongla) and the porphyry molybdenum deposit(Sharang) is acidic intrusive rocks and multi-stage mineralization. 3. Using U-Pb dating, Re-Os isotope of molybdenite dating and Ar-Ar dating, compared with Lietinggang, Longmala, Xingaguo, Jialapu, Leqingla, Mengya’a, Dongzhongla, Yaguila, Sharang, Qiagong, Sinongduo, Narongsongduo in the north of the Gangdise, there is a separate iron polymetallic metallogenic belt in the Gangdese Nyainqentanglha magmatic arc, parallelling to the Pb-Zn mineralization belt on the south.