| The study area is located in the west of Yichun in Lesser Khingan Mountains,the early Mesozoic granites are widely distributed in this area,constitute a large scale of Mesozoic "granite sea" in northeast China.Belongs to an important part of Lesser Khingan Mountains in Heilongjiang province– Zhangguangcailing,Cu,Mo,Pb,Zn,Au,Ag,Fe etc.constitute a polymetallic metallogenic belt there,which is strongly associated with granitic mineralization.This paper mainly relies on the basis of research results of 1:50000 national basic geological survey project which developed in Lesser Khingan Mountains Yichun area in recent years.In terms of regional geology,collect and collate relevant information of Regional geologic features,strata,magmatic rocks and structurer to get a systematic and comprehensive understanding of the geological survey of the study area.In terms of age,carry out isotopic chronological study of different lithology combination of granite to determine its age.In terms of geochemical,through major and trace elements of granite and rare earth elements to discuss its petrogenesis and tectonic setting in different aspects.In terms of regional mineralization,combined with regional geological,focus on ore rocks,tectonic,alteration and ore-Forming geological conditions of main mineral type in study area,summarizes the Metallogenic regularity.Through the above methods to study the granites of Mesozoic in study area,author reached the following results:(1)Ages LA-ICP-MS zircon U-Pb isotopic in the monzogranite and syenogranite are 190±1Ma and 189.3±1.4Ma.Their diagenetic age is mainly concentrated with 189 ~ 192 Ma,which is the product of structural magmatic activity in the same period.Its age is tentatively intended to the early Jurassi.(2)The Early Jurassic granite changes from the early diorite to late metamorphic granite magma source area,transits from early impact extrusion of volcanic arc property to late tension crust-mantle mixed-source zone property.magmatic source area is mainly in the form of subduction and collision,which is related to the action of the earth's crust.Granodiorite and adamellite was formed in the same collision of the tectonic environment,but syenogranite is formed in postorogenic tectonic setting.The western region of Yichun in the Lesser Khingan Mountains of east Heilongjiang Province was in tensile stretching in the early Jurassic,deep-focus mantle material upwelled,which also caused the partial melting of the crust and formed a set of orogenic granites in the extended environment.However,granodiorite,monzonite granite and syenite granite's differences in chemical composition of rocks reflect the different magma sources,further identified that early jurassic granite's main body is made up of a complete set of magmatic evolutionary series of granodiorite ?syenogranite.(3)The granite porphyry of the early cretaceous is characterized by volcanic arcs.Its formation is closely related to the subduction and reduction of the plates.In the process of the mantle-derived magma,the granite porphyry of early cretaceous is formed by the mixture of crust material.It is the product of movement in the late-stage magma of the western Pacific plate.(4)Delineated mineralization prospecting area which is in connection with the early Mesozoic granite including copper,lead and zinc in Fuyu River-Jianshan River ? mineralization prospecting area and Yuejin Forest ? mineralization prospecting area. |
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