Petrological Characteristics Of Intrusions Of C?P Stage In The Yakeshi Distric,and Its Geological Significance

The studied area,yakeshi,is located in the central-north part of Great Xing,an Range,tectonically situated on the eastern part of Central Asian Orogenic Belt between the North China plate and Siberia plate.Based on the comprehensive research,the granitic rocks were classified into two stages:the early-stage Dioritoids which distributed mainly in the northwest side of the Toudaoqiao-Wunuer matching belt include the series diorite-quartzdiorite-granodiorite-tonalite-biotite granite whereas the late-stage granitoids which is mainly in the opposite side of the suture zone include the series monzogranite-syenogranite.The early-stage dioritoids are a set of calc-alkaline rock series in general,with the characteristics of typical ?-type intrusions,and the zircon LA-ICPMS U-Pb age is 314Ma?328Ma;however,the late-stage granitoids are a set of alkaline rock series in general(based on SiO2-AR diagran),With the characteristics of highly fractionated?-type granitoids,and the zircon LA-ICPMS U-Pb age is 274Ma?309Ma.The paper considers that the early-stage dioritoids have a source residure of eclogite.facies without plagioclase while the late-stage granitoids have a source residual of amphibolites faces without garnet.The studied area was determined to be volcanic arc in the stage of 314Ma?328Ma which associated with the northwest subduction of Paleopacific plate(between songnen terrane and xing'an terrane),and formed a.massive amount.of typical ?-type dioritoids;Age to the stage of 274Ma?309Ma,the studied area was in the position of the back-are and formed a massive amount of highly fractionated?-type granitoids including a few S-type granitoids.