Study On Metallogenic Regularity Of Porphyry Copper Deposit In Nimu-mozhugongka Area, Gangdise Metallogenic Belt

Study area is the eastern section of Gangdise metallogenic belt which is located on the northern side of Yarlung-Zanbo river, and the Geotectonic location of study area is Gangdise Volcanic-magmatic Arc (J-K). Tectogenesis-magmation happened frequently in the area, a lot of intermediate acid intrusions and Mesozoic-Cenozoic volcanic-sedimentary strata distributed along the tectonic-magmatic belt. There had more tectogenesis such as Neo-Tethys oceanic crust splitting & subduction action, plate collision between Indian plate with Eurasian plate, Qinghai-Tibet Plateau uplift and other tectogenesis after Neopaleozoic in Gangdise metallogenic belt. With the tectonic evolution, there happed a lot of magmation and metallogenesis, tectogenesis-magmation have a close relationship with metallogenesis.Gangdise metallogenic belt is an important porphyry copper belt in China ,Nimu-Mozhugongka is one of the most intensive porphyry copper deposit distribution area in Gangdise metallogenic belt. A lot of porphyry copper deposits such as Bairong, Gangjiang, Chongjiang, Tinggong, Dabu, Lakange, Qulong and others are distribute from west to east in the study area, and a lot of Skarn type copper-polymetallic deposits such as Tangbala, Jiama, Zhibula are distribute on the periphery areas of porphyry copper deposit.The paper selects Nimu-Mozhugongka as study area, summarized the achievements of former researches and had filed geological investigation, the paper extracted the distribution information of fault, instruction and deposit with the multi-source & multi-level prospecting information extraction method, and summarized the distribution characteristics of tectonic and deposit. Combined with the tectonic evolution and the characteristics of typical porphyry copper deposits, the paper analyzes the relevance and evolution regularity of tectogenesis-magmation-metallogenesis, and summarizes the metallogenic characteristic and regularity of porphyry copper deposit. The main contents and the main research results obtained as follows:(1)Based on the remote sensing interpretation of geological structure and the character analysis of linear structure, the paper indicates that linear structures in Gangdise metallogenic belt have zonal characters in south-north, and have differences in east-west.The remote sensing technology has advantage in acquiring the macro feather of areal geology, the paper extracts the information of linear structure with remote sensing technology and indicates that linear structure zonal distributes in east-west, and divided into three belts (south-middle-north) according to local characteristics. The characteristics of geological structure on the east side of Dangxiong-Yangbajing fault are different from the characteristics of geological structure on the west side, there formed difference linear structure system in the both sides.(2)Based on the analysis of spatial distribution characteristics of geological structure and deposit, the paper studies the relationship between geological structure and deposit at different spatial levels, and summarizes the spatial distribution regularities of deposits.The paper analyzes the relativity of geological structure and deposit at various spatial levels such as metallogenic belt, ore concentration area and typical deposit. The deposit zonal and nearly equality distributes in east-west, and concentrated distributes in some areas so as to form ore concentration area. In respect of ore-controlling structure, the metallogenic characteristics of Gangdise metallogenic belt are controlled by the first grade structure (e.g. Yarlung-Zanbo suture), the metallogenic characteristics of ore concentration area are controlled by the second grade structure (e.g. the fault on the margin of secondary structure), the distribution of deposits are controlled by the third grade structure, the positions where linear structures stack with circular structures are the favorable environment for mineralization. Coupled with geological data, the paper indicates that Chongjiang-Tinggong, Lakange-Qulong and other ore concentration areas distributed on the margin of Lhasa interarc basin, where are the transition belt between the basin and mountain. The positions near the boundary of secondary structure units (e.g. the transition belt between the basin and mountain) are the main distribution areas of porphyry copper deposit.(3)Analyzed on the distribution characteristics of geological structure and deposit, the paper indicates that tectogenesis and magmation have close relation with metallogenesis, geological structure and magma are the main ore-controlling factors of the porphyry copper deposit in the research area, coupled with tectogenesis and magmation, the metallogenesis of porphyry copper occurred in the area.Tethys expansion, plate subduction, collision orogeny, plate syntaxis and extensional strike-slip in post-collision stage and other tectogenesis coupling with multiphase volcanic-intrusive magmation after Neopaleozoic provide the favorable background for metallogenesis in Gangdese metallogenic belt. The porphyry copper(molybdenum) deposit formed in Miocene epoch(18~13Ma) when Gangdese orogenic belt transition from collision orogeny stage to extensional strike-slip stage. In terms of space and time, the diagenesis and metallogenesis synchronize with the tectonization- magmation in Himalaya period. The spatial distribution of deposit are double controlled by the tectonic zone and volcanic-magma belt, the metallogenesis in the area are characterized by multiphase, and have close relationship with the intermediate acid hypabyssal porphyry mass which intruded along the fault in Himalaya period.(4)Metallogenic prognoses are made at the end of the paper according to the metallogenic characteristics of porphyry copper deposit.Researched on the metallogenic characteristics of porphyry deposit, the paper delineates the ore prospective area and indicates that there have huge prospecting potential in the area. The periphery and deep of Chongjiang-Tinggong, Dabu, Lakange-Qulong and other metallogenic provinces are the key prospective area.(5)Established and applied concretely of the multi-source &multi-level prospecting information extraction method.The paper extracts the multi-level prospecting information and researches on the metallogenic regularity of porphyry copper deposit. There have some innovation and improvement about the multi-source &multi-level prospecting information extraction method, which provided technical references for the prospecting work in study area.