Geochronology And Geochemistry Of Suotuhan Pluton In The Northern Great Hinggan Range And Its Tectonic Significance

This paper summarizes the geochemistry,zircon U-Pb ages of the Suotuhan Pluton K-feldspar granite and tectonic setting in northern Gerat Hinggan Range.The studies of the K-feldspar granite in this area will be significant in discussing the regional tectonic evolution in Gerat Hinggan Range.The LA-ICP-MS zircon U-Pb dating results of the samples are 139.5�0.56Ma,144�0.85Ma.it can be concluded that the Suotuhan Pluton K-feldspar granite were formed in Early Cretaceous.The Suotuhan Pluton K-feldspar granite in srudied area is characterized byhigh-SiO₂and alkali-rich,which belongs to high-K calc-alkaline series rocks,weakly peraluminous-peraluminous?0.99¹.04?.Fractionation of light rare earth elements is better,positive abnormality of Ce and strong depletion of Eu.Trace elements data show that they are enriched in Rb,Th,U,Ta,Hf and depleted in Ba,Sr,P and Ti.The zircons saturation temperatures of these granites are very high,which shows the same characteristics with A-type granites.In 10000�Ga/Al-Ce,Nb,Na₂O+K₂O ect.diagram,all fall into A-type granite distribution area.The K-feldspar granites in the Suotuhan intrusion are characterized by very low Sr,high Yb type granites and high Si,relatively alkali-rich,calcium-poor and magnesium-poor.It can be concluded that the K-feldspar granites in the Suotuhan area are the products of partial melting of lower crustal rocks.The Suotuhan Pluton K-feldspar granite formed in the post-tectonic extension environment.The stretch of tectonic setting may be closely related to the orogenic belt stretch after the Mongol-Okhotsk Ocean closure.