| This paper focused on three categories of porphyry-type Cu, Mo polymetallicdeposits, which situated on the eastern of Gandise metallogenic belt, Tibet. Study ongeologic feature, magmatic activities related to the regional tectonic evolution,geochemical characteristics of three typical deposits, according to discuss deposit’stype, ore-controlling conditions and metallogenic regularities, to established regionalstructural-ore controlling model.Gandise volcanic-magmatic island arc was distributed on the northern YarlungZangbo River Collision belt. From Late Paleozoic Era to the Mesozoic Era, island arcunder plate subduction, to formed composite volcano-magmatic arc belt. It becomesone of the most important metallogenic belt and even the whole country. Throughgeologic&mineral resource prospecting work, it already become one of mostimportant resource base in China.From the author’s view, during the phase of oceanic crust subduction, Xiongcuncopper-gold deposit stand for Porphyry copper gold formation, with late-stagesuperimposed mineralization. There are:1)study on ore-controlling structure inXiongcun copper-gold deposit,“two fault with one fold” ductile-brittle property tocontrol the distribution of ore body.2) study on the ore characteristics, geneticmineralogy indicated that Xiongcun copper-gold deposit own the metal mineralcombinatorial complexity.(sphalerite combined with14kinds of metal minerals,chalcopyrite with16s), same mineral with multiple occurrence status, same mineralwith different typomorphic-type, same typomorphic with complexity combination, et,al.these phenomenon shows it exist multi-periods, and superposition mineralization.3)monomineral REE geochemistry shown the total content of quartz rare earth elementswith four generation（∑REE=0.596706～5.423752（×10-6））greater than totalcontent of pyrrhotite, pyrite（（∑REE=0.126854～0.883578（×10-6））, from earlygeneration to late generation, total content of quartz REE has a growing tendency,LREE enrichment degree has a decreasing tendency, HREE loss degree has decreasingtendency, HREE of sulfide higher than Chloride quartz. It turns out ore-fluidsuperposed mineralization derived from basic magma, and high oxygen fugacity, et,al. 4）geochemical characteristics of trace monomineral trace elements show that metalsulfides related to basic and neutral magmatism, hydrothermal properties of multistagemineral varies markedly.5) Isotope geochemical characteristics shows multistageSuperposition metallogenic. Both mineralization backgrounds of Pb isotope shows thatthe composite area oforogenic belt&ocean island, and magma source area&magmaticemplacement had a certain relationship with underthrusting&orogenesis. ore-formingmetal material in source area between upper crust and mantle, even more with mantle.Source area of sulfide comes form magmas/deep source. Oxyhydrogen isotopegeochemistry mainly magmatic water, with few formation water. However, fewformation water in ore-forming activities, more formation water at the front part.6)monomineral Pb-Pb model age&quartz HAESRDQ52.7～70.4Ma., which showsmultistage superposition mineralization.In the collision background, Sharang molybdenum deposit belongs to Porphyrymolybdenum deposits, study shows that:1）study on deposit geology, explorationgeochemistry characteristics and exploration geophysical characteristics, Porphyrymolybdenum deposits belongs to collision background, indicator element W-Bi-Mo-Re、Zn. Highly mineralization area has lower resistance, medium-high polarizationfeatures(Polarimetric can reach12％).2) Through alteration mapping, establishdeposits alteration model, show the earth’s surface of Sharang molybdenum depositmerely formed in clayiztion-sericitization belt, and overall denudation level very low.3)lithogeochemistry results suggests that ore-bearing rock mass belongs to Volcanic-typegranite, from calc-alkalic to high-K calc-alkalic to K-shoshonitic series. All rocks wasenriched by LREE&LILE(Rb，Th，Pb，P), deficiency in Ba，Sr&HFSE(Nb，Ta),granite porphyry of metallogenic deficiency in Ti.4) LA-ICPMS zircon U-Pb datingindicated that matallogenic rock age52.9±0.5Ma～52.3±0.4Ma-51.6±0.4Ma, Re-Osisotope dating of molybdenite52.01±0.20Ma，MSWD=0.58.5) Magma source areasituated in the area of damphibolite melting, eclogite area hardly consists of thickencrust. Miocene granodiorite-porphyry formation was partial melting in source region ofdiorite, mineralization rocks has partial melting with EMII.Qulong Cu polymetallic deposits was product in the stretch background andcollision process, indicated that:1) study on petrology of magmatic rocks,petrochemical characteristics, to ensure quartzdiorite, granodiorite, biotite adamellite,granodiorite-porphyry, adamellite porphyry, allgovite, diorite porphyrite, quartzporphyry, Ansan porphyrite and granite appear in the form of stocks, apophysis anddike, to constitute a complex volcanic-magma system.2) magma of Qulong mine areaderived from partial melting of new lower crust. In the late stage, increasing ancientmaterial from magma source area.3) study on orebody geological, alteration zoning,geophysical exploration, geochemistry characteristics exploration and remote sensingcharacteristics, to summarized deposits guiding, to establish the model of deposits.To sum up,Cu-Mo features in the main porphyry deposit of Gandise metallogenic belt belongs to mantle, Mo own the lower crust features, Pb mainly derived from stablecratonic crust-Pb,Zn derived from crust. Deposit space distribution exists somedisparities, and point out: prospecting potential of mesozone is maximum in theGandise mineralization belt.According the zircon LA-ICP-MS U-Pb age of intermediate-acidic intrusive rocks,roughly divided the magmatism of Gandise porphyry metallogenic into three phase:200～80Ma、60～45Ma、25～10Ma, the consequence mineralization concentratedin three phase:180～160Ma、65～40Ma、20～12Ma, thus formed island arcbackground of Xiongcun porphyry copper gold deposits, continental interiors collisionbackground of Sharang porphyry molybdenum deposits, collision-extensionalbackground of Qulong porphyry Cu(Mo) deposits,et,al.Thus, according to regional tectonic evolution, established tectonic-magmaticore-control model of Paleocene-Eocene flower-like nappe structure fan in the YarlungZangbo suture zone, thrust-gliding model of Gandise mesozone, thrust fan-magmaticcontrol model of northern Gangdise metallogenic belt.Innovations of this paper:1）Set up multistage composite mineralization of Gandise Cu(Au) deposits.2） Establish tectonic-magmatic deposits control model of Paleocene-Eoceneflower-like nappe structure fan in the Yarlung Zangbo suture zone, thrust-glidingdeposits control model of Gandise mesozone, thrust fan-magmatic deposits controlmodel of northern Gangdise metallogenic belt.3）Bring up ore-forming geological settings was the response from Yajiangthrusting to collision. |
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