| Yichun-Yanshou metallogenic belt is located in the eastest part of central Asian orogenic belt that is on active collaged zone between land mass of Jiamusi and Songnen. The Yanshanian granitic magma activity dramatically and form the granitic rocks who is accompanying a large number of Fe-Mo metal ore deposit in research area by the double impact of the regional tectonic system of the Pacific Rim and ancient Asian Ocean. Based on discuss the time-space evolution,origin and tectonic background of Yanshanian granitic Combined with the typical mineral anatomy, explore the inner-related between igneous activity and regional mineralization in research area.Yichun-Yanshou granitic rock Mainly includes granodiorite, Monzonite granite and granite porphyry, syenogranite who has a wide distribution range. granodiorite, Monzonite granite are NE, NNE to linear distribution in the study area, Granite porphyry in the form of smaller rocks output with volcanic rocks. The study concluded that biotite adamellite, adamellite of Cuihongshan U-Pb age is 198.3±3Ma、198.9±1.6Ma, biotite adamellite, adamellite of Luming U-Pb age is 194.8±0.7Ma、176.2±2.1Ma, Granite porphyry of Wudaoling U-Pb age is 194±2.4 Ma; the result of U-Pb isotopic test show that Yanshanian granitic in Yichun-Yanshou metallogenic belt occurs mainly in the early Jurassic who related to mineralization.Yichun-Yanshou granitic rock major element show that the granites are high potassium calc-alkaline-weak-alkaline, metaluminous-peraluminous a-type granites, rich in Si, K-Na and Al. The granties were enriched in LILE(Rb, Th, U, K) and light rare earth elements, depleted in HFSE(Nb, Sr, Eu, Ti). Distribution patterns of the rare-earth element are similar, right-light rare, left-heavy rare and Has obvious Eu anomaly, showing that they might be comagmatic products and Plagioclase residual source area. Trace elements and isotopes confirmed granitic magma is not only has characteristic of crustal magmatic, also has the display of the mantle-derived magmal composition,they might be crust-mantle products.Yichun-Yanshou granitic rock has geochemical characteristics of who formed in in volcanic arc and collision tectonic environment,belong to A2-type granite of A-type granite, The rock formation might be relative to crustal magma riched in mineral formed in partial,elting of the lower crust induced by underplating of mantle-derived basaltic magma. and the crustal magma occurs contamination of crust an mantle with the mantle-derived basaltic magma.It suggests that Yichun-Yanshou granitic rock might be the late orogenic extrusion and intermittent stretching environment products under the condition of bidirectional subduction of the Mongol-Okhotsk teceonic system and Circum-pacific tectonic system.Through the study of Yichun-Yanshou granite and key mining area, main ore-hosting strata are Wudaoling group and Qianshan group, the Leading to metallogenic rock mass main is Monzonite granite syenogranite and granite porphyry. Yilan-Yitong deep fracture is the main ore-controlling structures which is along the NE to distribution. Wall rock alteration mainly silicification, sericitization and skarn alteration. δ34S value of S isotope between 3.68‰ to 5.68‰, it show that mental ores may come from the mantle-derived magma and might be occurs contamination of other sources of S. Ore-forming fluid Has the characteristics of middle-high temperature, middle-low density, large Salinity range. It is suggest that Ore-forming fluid is the result of the mixture of magmatic water and atmospheric water, belongs to hypabyssal environment who Conform to the characteristics of the porphyry deposits. In combination with others molybdenite Re-Os age, found that in the region diagenetic and metallogenic all formed in early Jurassic.Under Subduction extrusion tectonic background of the Pacific Ocean, asthenosphere upwelling one side Provide a large amount of heat, partial melting in the crust, and blending in with the upwelling of mantle-derived magma formed regional magmatic hydrothermal mineralization system; another side in the process of crust-mantle magma mixed, elting of the lower crust induced by underplating of mantle-derived basaltic magma bring a lot of Pb,Zn,Mo,Fe metallogenic elements and enter regional magmatic hydrothermal mineralization system. At the same time,they along with the deep faults formation of Yilan-Yitong upwelling. With the continuous crystallization differentiation of magma, ore solution separation gradually. Part of them intrusion into carbonate rocks formed skarn deposits; the otherdue to the change of temperature, pressure and solution state of internal components in the process of migration, leads to the metallogenic elements precipitation in the same period magmatic granite porphyry formed Porphyry-type deposit. Eventually it formed the Yichun-Yanshou Yanshanian granite belt and Related Mo deposit. |
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