Zircon U-Pb Dating And Geochemical Characteristics Of Granitic Rocks In The Steinnes Peninsula Region,East Antarctica

There are different types of granitic rocks in the Prydz Bay area of the southeast Antarctic.Previous studies on granitic rocks in places such as Lassman Hills in Prydz Bay have been carried out to varying degrees.However,few studies have been done on the Steinnes Peninsula and its nearby islands.Lacking of detailed chronological and geochemical studies,and there is short of in-depth understanding on the age and origin of its formation.In this paper,petrology,whole-rock geochemistry and zircon U-Pb chronology of the granitic rocks from the Steinnes Peninsula and its nearb islands in the Prydz Bay region of the southeast Antarctic have been comprehensively analyzed,and the following conclusions have been obtained:(1)The granitic rocksin the Steinnes Peninsula are mainly composed of granite containing biotite,muscovite and garnet.The mineral composition of granite containing biotite and muscovite is quartz + potassium feldspar + plagioclase ± biotite ± muscovite and a small amount of apatite,zircon,etc.The mineral composition of granite containing garnet is: quartz +plagioclase + potassium feldspar + biotite ±sillimanite± garnet and a small amount of apatite,zircon,etc.(2)Zircon U-Pb dating of granitic rocks from the Steinnes Peninsula and its nearby areas(islands)indicates that the emplacement ages of the granitic rocks are about 512?530Ma(the Pan-African period).The emplacement age of the granitic rocks in the Steinnes Peninsula is close to or slightly later than that of the regional peak metamorphism(530?545Ma),and the age of the granitic rocks is close to the regional peak metamorphism,which also indicates that the region experienced a strong tectono-thermal events during the Pan-African(?550Ma).(3)In terms of geochemical characteristics,the composition of granitic rocks from Steinnes Peninsula varies greatly,which arecharacterized by strong peraluminous characteristics with Al saturation index A/CNK=1.27?1.79.It is consistent with the occurrence of characteristic secondary aluminum-rich minerals(muscovite,sillimaniteand garnet)in the rocks,showing the characteristics of strong peraluminous S-type granite.Rich in potassium,low in calcium,low in magnesium and low in iron.Except for the positive anomaly of Eu,the heavy rare earth(HREE)exhibits aright-leaning distribution pattern of loss and enrichment of light rare earth(LREE).Negative anomalies of Nb,Sr,P and Ti appeared in the spider web.The estimated diagenetic temperature of the Steinnes Peninsula granite ranges from 595 to 865,Which roughly clustered around 700.The peraluminous S-type granites at Steinnes Peninsula should have been formed by partial melting of metasedimentary rocks in the crust.