| The group of massifs of Northeast China is located between the Siberia Craton, North China Craton and Western Pacific Plate, which have occurred large scale of structural deformation, magmatism and polymetallic mineralization, drawing lots of geologists around the world focused on this area. However, the tectonic backgroud of the igneous rocks is still on controversial. For this, we choosed three represented plutonic granitiods of Yichun-Yanshou Metallogenic Belt like Huojihe pluton, Luming pluton and Cuihongshan pluton as this study objects. We carried out the petrology, geochronology and geochemistry trying to understand the origin of the granitiods of Yichun-Yanshou Metallogenic Belt and their tectonic backgroud.Early works shows that the Yichun-Yanshou Metallogenic Belt is a sub metallogenic belt of Lesser Hingan Range-Zhangguangcai Range Metallogenic Belt. The plutons of this study located at the north of Yichun-Yanshou Metallogenic Belt, from north to south are Huojihe pluton, Cuihongshan pluton and Luming pluton. Huojihe pluton which is the host rock of porphyry deposit, also composed of granodiorite and monzogranite and the granodiorite related with the Mo mineralization. Cuihongshan pluton which is the host rock of skarn deposit, composed of granodiorite and monzogranite and the granodiorite has close relationship with the Fe mineralization and the monzogranite related with the Pb-Zn-Cu mineralization. Luming pluton is the host rock of porphyry deposit, composed of monzogranite and granodiorite, and both of them have relationship with the Mo mineralization.Zircon LA-ICP-MS U-Pb dating suggested that the age of the Cuihongshan monogranite is 484±4.7 Ma and the age of the monogranite is 198.9±1.6 Ma, repectively. Luming biotite-granodirite is 199.0±3.2 Ma, the age of the monogranite is 176.2±2.1 Ma, indicating that the magamatic activity through the whole time of early Jurassic. The Jurassic magamatic activity of Luming is consisted with the magmatic activity of Cuihongshan in Jurassic. Based on reported data that the Huojihe granotiods have the age of 184.0±1.5 Ma. Summarized the reported magmatic activity age data of this area and adjacent area, we suggested that the Yanshanian is an important epoch in Yichun-Yanshou Metallogenic Belt.Whole rock geochemistry indicating that the Huojihe and Luming granites are charatized by high SiO2, high Mg#, high Sr/Y and (La/Yb)N and low Cr, Ni contents, which have the affanity with the adakites drived from the delamination of the Crust. The granites from Cuihongshan have characters of high SiO2, Na2O+K2O, and enriched in Rb, Th, U and Pb, depleted in Ba, Sr, Nb, Ta, P, Ti and Eu, like A-type granite.The granites of Huojihe pluton, Luming pluton and Cuihongshan pluton are all enriched in Rb, Th, U, Pb and light rare elements(LREEs) and depleted in Ba, Nb, Ta and Ti. The whole rock Sr istopic elements and S istopic elements show restricted ranges, with 87Sr/86Sr between 0.706 and 0.709 and ?34S between 3.68‰ and 6.71‰. Combined with the previous study of Hf model age and Sr-Nd-Pb isotopic elements of this district, we suggested that the primary magmas are derived from Crust-depleted mantle interaction, which had been metasomatized by subducted slab-derived fluids/melts. The early Yanshanian magmatic-metallogenic events in the Yichun-Yanshou Metallogenic Belt are interpreted as a response to the postorogenic of the collision of the Jiamusi Massif and Songliao Massif which triggered by the subduction of the Paleo-Pacific Plate. |
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