Geochemistry And Tectonic Setting Of Early Jurassic Granites In Yanshou Area,Heilongjiang Province

Yanshou County of Heilongjiang Province is located in the east of Heilongjiang Province.It is located in the Songnen-Zhangguangcailing massif in the eastern part of the Central Asia Orogenic Belt.It sandwichs between the Siberia Craton and the north China Craton.It belongs to the Yichun-Yanshou magmatic belt.The early Jurassic Granites are widely exposed in the study area.The rock types include Monzonite,Syenite and Alkali Feldspar Granite.The origin and mechanism of Mesozoic magmatism in the eastern part of Heilongjiang have been disputed by scholars.Some scholars believe that it is influenced by the tectonic evolution of the Paleo-Asian Ocean,others think it is influenced by the evolution of the Circum-Pacific Ocean.In this paper,it's reported that the zircon LA-ICP-MS U-Pb dating and geochemical results for the early Jurassic granites within Yanshou area in Heilongjiang province in order to constrain the formation ages as well as their tectonic setting.The study area is located in the Lesser Xing'an-Jiamusi Mesozoic tectonic-magmatic belt.The Early Jurassic granites in the study area are widely exposed,and the rock types include monzogranite,syenogranite and alkali feldspar granites.The dating results indicate that the formation ages of monzogranite,syenogranite and alkali feldspar granites are 191 ± 1 Ma,199 ± 1 Ma and 189 ± 1 Ma,respectively.Geochemical characteristics of Early Jurassic granites in the study area indicate that they belong to typical I-type granitic rocks,have the characteristics of the series of high potassium calcium alkali and low aluminous rocks in the series of oversaturated aluminum.These findings,together with their geochemical characteristics and regional early Mesozoic tectonic evolution history,suggest that the formation of Early Jurassic granites in the study area is related to the subduction of the Paleo-Pacific plate under the Eurasian continent in Early Jurassic.