Copper-iron Polymetal Metallogenic Regularity And Election Of Targeet Areas In The Western Of Gangdise Metallogenic Belt, Tibet

The western Gangdese belt located in the south of Tibetan Plateau, experienced an evolution history including subduction orogeny of south and north Tethys oceanic basin, collision orogeny of Lhasa block-Qiangtangterrane-Himalayan terrane and intra-continental orgney at post-collision since the late Paleozonic, which developed several huge magmatic arc belt, and associated with iron-copper polymetallic mineralization at the same time. The deposit types can be divided into porphyry Cu(Mo,Au) deposit, skarn CuFe(Pb,Zn,Ag,Au) deposit, volcanic hydrothermal and magmatic hydrothermal type CuPbZn(Ag,Mo,W,Bi,Sn) deposit, etc.This thesis based onthe system study on metallogenic background, metallogenic environment, metallogenic conditions, metallogenic regularity, anomaly extraction and screening methods, made a series of progress on Cu-Fe polymetallicmetallogenic theory and practice at the western Gangdese belt. The main progress and understanding are as follows:1. Supplementing and improving the typical deposits metallogenic theory research in the western Gangdese, and discussing and summarizing the metallogenic characteristics, metallogenic environment and the genesis of different types of depositsAccording to the genesis types, the copper-iron polymetallic deposits in the study area can be divided into porphyry copper-gold deposit, porphyry copper-molybdenum deposit, porphyry-skarn copper-iron-lead-zinc deposit, skarn copper-iron-lead-zinc deposit, skarn iron deposit, skarn lead-zinc-silver deposit, skarn copper-gold deposit, volcanic cryptoexplosive breccia type lead-zinc-silver deposit, volcanic hydrothermal type lead-zinc-silver-tin deposit, magmatic hydrothermal type copper-lead-zinc deposit, hydrothermal type copper-silver deposit, etc.Different types of deposits are closely related to the volcanic-magmatic activity in the different times and different tectonic settings. The porphyry deposits mainly formed in the island arc, collisional, post collisional extensional environment, and predominately distributed in the four period which consist of the early time of Middle Jurassic, Late Cretaceous, Eocene, Miocene; The skarn deposits mainly formed in the island arc, collisional, post collisional extensional environment, and predominately distributed in the three period of Early Cretaceous, Late Cretaceous and Paleocene Eocene; The volcanic hydrothermal deposits formed in the island arc, collisional environment, and concentrated in the two period of the Early Cretaceous and Paleocene.2.This thesis systematically summarized the regional rock-controlling and ore-controlling factors.(1)The mainly stratas which are closely related to mineralization in the research area are the Cretaceous LangShan formation, Jiaga formation, Bima formation, Takenaformation,mamuxia formation and the middle permian series Xiala formation. The formation lithology of forming skarn type copper-gold deposit is limestone of intermediate volcanic rocks.limestone of siliceous rocks and volcanic rocks as formation lithology,which could forming lead-zinc deposit,the formation lithology of forming copper deposit are the crystalline limestone, siltstone, sandstone, etc.(2)The regional structures in the study area control the distribution of porphyry metallogenic belt (ore concentration area). The coupling area of the large magmatic belt and the cretaceous Marine sedimentary basin control the distribution of the skarn type deposits (belt). The thrust nappe structures mainly control the distribution of hydrothermal filling type copper lead-zinc deposits and the ductile shear zones controlled the output oftectonic altered rock type gold deposits.(3)There are two metallogenic characteristics of the volcanic rocks, the southern Lin Zizong group volcanic rocks mainly form the cryptoexplosion breccia type and the type controlled by structures lead-zinc-silver deposits; In the meanwhile, the northern Zenong group volcanic rocks mainly formed (subvolcanic) the volcanic hydrothermal type silver Cu-Pb-Zn-Sn deposits which are hosted by structures. All of these deposits’output are controlled by the faults that are in the edge of volcanic fault basin or the volcanic apparatus. The mineralization were formed in middle-late of the volcanic activity.(4)The copper iron gold polymetallic mineralization possess the characteristics of obvious multi-stage and centralized distribution that are controlled by the intrusive rocks in the study area. The petrogenic age related to the mineralization were concentrated in nearby peak of 115,90,80, 65 and 15 Ma, and following by are 175 and 140 Ma. The metallogenic rock-bodies of porphyry and skarn copper-iron deposits, possessing the characteristics of augen quartz phenocryst, are mainly quartz porphyry, granite porphyry, granodiorite and biotitemonzonitic granite, and belong to the the mantle source-lower crust source I type granite; However, The metallogenic rock-bodies of lead-zinc deposits are mainly granite porphyry and quartz porphyry, and belong to the shell source S type granite.3.Systematically divided the west Gangdese Ⅳ、Ⅴ metallogenic belt, and summarized the regional spatial distribution laws.In the study area there were two porphyry type copper polymetallicmetallogenic belt, four skarn type copper iron lead zinc gold metallogenic belt, two hydrothermal filling type lead zinc polymetallicmetallogenic belt, one structural altered rock type gold metallogenic belt, one magmatic type chromium nickel iron metallogenic belt, from south to north, appear in turn copper gold mine, copper molybdenum mine, copper iron lead zinc mine, gold and copper mine, chromium and nickel gold antimony lead and zinc mine, copper iron lead zinc mine. In the study area is divided into 13 grade IV metallogenic belt and the 31 grade V metallogenic belt, based on the division of national Ⅰ, Ⅱ, Ⅲ grade mineralization unit.4. On the basis of the detailed study on the time of forming rock and ore from the typical deposits in western Gangdese, I divide into five major metallogenic stage, and summarizes the law of time evolution.(1) The Cu-Au mineralization stage related to the northward subduction from the Yajiang oceanic basin during the early Jurassic:the metallogenic ages were concentrated in 180-170Ma and typical deposits were Xiongcun and Donggapu deposit. These deposits banded at the south of Gangdese belt and adjacent to the north of Yajiang junction belt. The deposit types were porphyry and epithermal Cu-Au deposits, which were metasomatised by the wedge mantle zone and the released fluid from the neo-Tethys oceanic crust in the subduction zone.(2) The Fe-Cu-Au-Ag-Pb-Zn mineralization stage related to the southward subduction from Bangong lake-Nujiang oceanic basin during the early Cretaceous:the metallogenic ages were concentrated in 120-110Ma and typical deposits were Nixiong, Shesuo, Longgeer, Zhulang, Balong, Doumaguo, Tiangongnile, etc. The main deposit types were skarn Fe-Cu deposits, volcanic hydrothermal Ag-Pb-Zn-Sn-Au deposits and magmatic hydrothermal Cu-polymetallic deposits. The Ag-Pb-Zn-Sn mineralization are new discoveries at present stage. The metallogenic magma rocks had the geochemical characteristics same as the island-arc and continental margin arc rocks. The diagenetic and metallogenic material might be derived from partial melting of crustal rocks, or came from crust-mantle mixing zone.(3) The Cu-Fe-Pb-Zn mineralization stage related to the syn-collision and post-collision from Qiangtangterrane and Lhasa terrane during the late of early Cretaceous to the middle of late Cretaceous. The skarn deposits had characteristics of porphyry mineralization such as Bazala, Galale, Gaerqiong, Cuoqinria, Bangbule and Jianglaangzong deposits, etc. These deposits built a porphyry-skarnmetallogenic system centered in small porphyries and the mineralization time were about 90Ma. These single skarn deposits such as Bangeria, Bangbule and Jianglaangzong,etc mineralized at about 75Ma. The εHf (t) of zircons from the metallogenicrokcs changed smaller, from positive to negative, decreased from eatlier to later. It showed the magmatic source area changed from the mantle to the middle-lower crust or mixed with crust-derived material. The genetic of rock types gradually changed from I-type granite to I-S type or became S-type granite.(4) The Cu-Fe-Pb-Zn mineralization stage related to the northward subduction from the Yajiang oceanic basin and the collision of Indian continent-European continent during the Late Cretaceous to the Eocene. The diagenetic and metallogenic time were mainly between the 70 ma and 45 ma, which is also the most important metallogenic stage in the whole research area. The mineral deposits include Jiru, Chagele, Qiagong, Dexin, Narusongduo, Sinongduo, Pusangguo and Renqinze etc. The main types of mineral deposits are composed of skarnPb-Zn-Fe deposits, porphyry Cu-Mo deposits, hydrothermal breccia Pb-Zn-Ag deposits, magmatic hydrothermal Pb-Zn-Fe deposits, and tectonic altered rock Cu-Au deposits and so on. Furthermore, it happened frequently that a representative combination of mineralization types in the same deposit consisted of porphyry and magmatic hydrothermal, skarn and magmatic hydrothermal, skarn and tectonic altered rock and so on. The ore-bearing porphyry mained formed from the Tethys oceanic crust metasomatised the mantle wedge. The magma mixed a certain degree of material from Lhasa crust during its ascent process. The metallogenic rocks of skarn deposits were S-type granite or I-S type granite which related to the partial remelting crust rock of the ancient Lhasa block induced by the under-plating mantle-derived magma caused by collision and back-arc extension of the continental margin.(5) The Cu-Mo-Pb-Zn mineralization stage related to the extension after the collision from the Indian continent-Asian continent during the Miocene. The Gangdeseorogenic belt changed from convergence-orogeny to extension-strike slippage. The diagenetic and metallogenic ages were concentrated in 25-15Ma. The typical deposits were Zhunuo, Chongjiang, Bairong, Gangjiang, Jiagang and Luobuzhen,etc. The main deposit types were skarn Cu-polymetallic deposits, followed by hydrothermal Cu-Pb-Zn deposits. The metallogenic material derived from the thickning lower crust and the partial melting of enrichment mantle.5.The methods and criterion of geochemical data processing and anomaly sieving had been studied and developed.(l)Puts forward the extraction and sieving of geochemical anomalies should abide by these principles that connotation, regional, comprehensive, efficient, emphasized endow the anomaly with geological connotation and highlight the anomalies related to mineralization, as far as possible to increase the proportion of the ore anomalies in the delineation of anomalies,and reduce field verification work.(2)The establishment of a data processing division principle:the different landscape partition must to separate, Similar geochemical background fields; the geological background and mineralization characteristics of subarea has intrinsic genetic connection with the geochemical field; for the difference of geochemical background fields is not obvious or reflect specific metallogenic tectonic environments (such as Cr, Co, Ni etc.) elements does not divide the geological and geochemical zoning, delineated sub area boundary should fully consider the migration problem of dispersion train anomaly and anomaly source.(3) The specific realize the compilation method of "metallogenic type of anomaly map", "element anomaly complexity map".6.The research on extraction of ore Prospecting Information and target optimization have been carried out systematically, and delineation a group of target area of prospecting value.There are a lot of prospecting target area have been delineated, contain 10 porphyry type copper polymetallic ore,48 multiple genesis Cu Fe Pb Zn Ag polymetallic ore,9 multiple genesis gold-copper ore mainly. Among them, Chajiasi, Gongma, Dongcuo, Zhongnong, Bangbule, Sangmola, Balong, Rendui, Baliele, Nuocang, Zhaobo and Jiesacuo etc. area have great prospecting potential, are expected to find new ore deposits or ore occurrences.7. we had found some new deposit types and mineral types for the first time, and widen the field of prospecting vision.we first found a Ag-Pb-Zn-Sn (Balong) ore deposit which hosted in the volcanic rocks in Nyainqentanglha area, a Bi mineralization zone in Bange-Nima-Geji area, and found some Sn-Au mineralization clues in southern of Gangdise area. These new findings widen the field of prospecting visiongreatly.8.Verification of prospecting target area made significant discovery.Through the verification of target, there are three lead zinc silver depositswere found with large middle type ore deposits prospect, five target areas discovered copper polymetallic mineralized points or ore occurrences and clues for prospecting, and more than ten small mineralized points and prospecting clues.Copper resources potential totaled more than one million tons,Pb+Zn is more than three million tons, the rich iron ore more than fifty million tons, Ag is more than 2000 tons and Sn more than 200000 tons.