| In the history of continental crust formation and development, granitoids played a very important role and it was one of the object in geology science research. The formation and evolution of granitoids, whose activity was controlled by the activities of plate tectonics, was closely related to tectonic environment and the evolution of the crust. The granitoids were major component of continental crust and the direct result of tectonic movement, and their geochemical characteristics can reflect the the nature of the source region, also they were important magma records of tectonic time.It was found that granites with varied causes of formation were formed in different tectonic environments and showed different geochemical characteristics. Granite types and tectonic setting has been always an important theoretical and practical significance in earth science research, with different opinions and heated debate for a long time. In the 20th century, 70s, Chappell and White divided into two types of granites: I-type granites and S-type granites. In 1980s, a number of scholars related causes of granites and tectonic environment and put forward many granites classification programs. According to material sources, modes of the formation and tectonic location, Xu Keqin divided granites into continental crust transformation type, syntectic type and mantle-derived type. In 1990s, it was more thouhgt about the interaction between crust and mantle, and that the components of granites were affected by many factors such as tectonic environment, source rock composition, melting conditions, physico-chemical reaction, crustal contamination, magmatic evolution mechanism. Therefore, the causes of granites and tectonic environment research should be considered not only the source of rocks and classical dynamic features of plate tectonics, but also from the regional and temporal evolution. Songpan-GarzêOrogenic Belt, which had been known as Chinese"Geological Bermuda"and"Geological Museum", located in the east of Qinghai-Tibet Plateau, and went through Paleotethys Orogenesis and Neo-Tethys Orogenesis. Tectonic trackway was so complicated, but principal distortion occurred in Late Triassic Epoch. In Songpan-GarzêOrogenic Belt, intermediate-acidic intrusive rocks, which outcropped extensively and emplaced in Triassic Xikang Group, were one of the important part in the development of orogenic belt structure, and complex tectonic evolution of the region was paid a wide attention. Researching on granitoids in Songpan-GarzêOrogenic Belt, it can be revealed the nature of the crust source region, petrogenesis, and many important informations in complex history of tectonic evolution and dynamic mechanism. As yet, many granite bodies in this Orogenic Belt has been researched in detail, which involved geochemical characters, geochronology, petrogenesis mechanism etc. However, the research on granitoids in Yanggonghai area were merely built on the basis of age of geochronology, and it was lack of geochemical characters, genesis etc.This paper relyed on the"Project of China Geological Survey: 1:25 million Ruoergai County, Hongyuan County, Luhuo County, Barkam County Geological Survey measured the regional repair"which assumed by Sichuan Geological Survey. Investigating on the granite bodies in Yanggonghai area (involve Yanggonghai body and Dagaizhai body, Erdaoqiao body, Jianke body etc. in its neighboring area), combining regional geological setting, using petrology, mineralogy, geochemistry, geochronology etc., it was researched geochemical characters of main elements and trace elements in the area, analysised Zircon U-Pb geochronology characters. Moreover, this paper cited a number of data on previous results, such as one Sr-Nd isotope and two zircon SHRIMP U-Pb dating data of Yanggonghai body by Hu Jianmin, as well as several trace elements data by Zhao yongjiu; in addition, it was analyzed and compared with geochemical characters of southern China granitoids. Based on these studies, it was discussed the formation mechanism and tectonic environment of the granitoids in the area.By this research, it was recognized that:1. From the geochemical characteristics of main elements, granites in the area can be roughly divided into two classes: monzonitic granites and granodiorites, both of which showed high-K calcium alkaline and metaluminous to weak peraluminous characters. Trace elements were enriched in LILE (large-ion lithophile element) such as Rb, Ba, Sr, Th, with negative anomaly in HFSE (high field strength element) such as P, Ti Nb. REE distribution patterns were steeply right tilted and smooth, and enriched in LREE, with similarδEu andδCe, which mostly had not obvious anomaly or weak negative anomaly. Similar trace element model and REE distribution patterns showed that the two kinds of granitoids were productions of comagmatic evolution, and evolved from granodiorites to (biotite) monzonitic granites.2. By LA-ICP-MS zircon U-Pb dating, it was found that Yanggonghai granite body were formed in Late Triassic Epoch (211.7±1.3Ma) probability, and the result was in accordance with age-dating results (Late Indosinian to Early Yanshanian) of many bodies in the area, so that the result may indicate that magmatic emplacement in Yanggonghai area might be happened in Late Indosinian. Moreover, based on the picked Proterozoic era zircon (899Ma～1505 Ma), it can be speculated that ancient continental crust fundus may existed in the under-part of Songpan-GarzêOrogenic Belt.3. Granitoids in Yanggonghai area possessed both characters of I-type granites and S-type granites, and showed the interaction between crust and mantle, which was mainly and probably the underplating by mantle magma. So it can be considered that granites in Yanggonghai area mainly formed from partial melting lower crust, with underplating by mantle magma. In addition, HREE and Y/Yb characteristics may reflect that the source region were mainly hornblende residual phases.4. Tectonic environment of granitoids showed post-collision granite characters in Yanggonghai area. Additionally, high-K calcium alkaline characters, crust-mantle dual characteristics, regional magma emplacement and intense folding orogenesis, all reflected the characteristics of post-collision. So it was can be speculated that granitoids in research area were probably formed in intracontinental post-collision environment after major collision; they belonged to syn-tectonic granites, and were the productions of regional large-scale orogenic movement.
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