Alkali-rich Porphyry Petrology And Geochemistry In Jianchuan In Yunnan Province

Cenozoic alkali-rich porphyry widely developed along the Ailaoshan-Red River fault zone in western Yunan.JianChuan is in the eastern zone,This paper exert a detail research to Cenozoic alkali-rich porphyry in this region by the means of field geology,petrography,whole rock geochenmical data and Sr-Nd isotopes and zircon LA-ICP-MS U-Pb ages and Hf isotopes analysis.Besides,the paper discusses deep process of magmatism in the area by analyzing the nature of the source and petrogenesis,Alkali-rich porphyry in JianChuan region include amphibole syenite porphyry and monzonitic porphyry of JinHe,biotite quartz monzonitic porphyry of YuZhaokuai,granite porphyry of TaoHua,amphibole quartz monzonitic and syenite of XiaoQiaoTou.Alkali-rich porphyry enrich of K,LILE and LREE,lack of HFSE and HREE and geochemical properties of the Eu abnormal is not obvious.Rocks can be invided into two types,shoshonitic and adakite.amphibole syenite porphyry,syenite and monzonitic porphyry have the nature of shoshonitic,belong to prealuminous alkaline potassium,with high Sr and Y geochemical characteristics,?Hf(t)value is-1.2~4.4,?Nd(t)value is-4.1~-2.5,T2 DM is 1.05~1.18Ga;Quartz monzonitic porphyry is similar to granite porphyry,the chemical properties of has the nature of adakite,belong to peraluminous high potassium alkaline-alkaline series,with high Sr,low Yb and Y geochemical characteristics,?Hf(t)value is-3.5 ~ 5.7,?Nd(t)value is-3.2~2.7,T2 DM is 0.62~1.11 Ga.The age of alkali-rich porphyry is 35.4 to 36.6 Ma in this paper.The age of amphibole syenite porphyry was 35.8 ±0.3 Ma,the age of syenite was 35.0±0.2 Ma,the age of the biotite quartz monzonitic porphyry was 35.4±0.2 Ma and 36.6±0.4 Ma,the age of granite porphyry was 35.5±0.2 Ma,the age of amphibole quartz monzonitic porphyry is 35.7±0.2 Ma,35.8±0.4 Ma and 35.6±0.2Ma.Containing inherited zircons of 816±3.6 Ma indicates that the basement of the neoproterozoic Yangtze platform inherited zircon.Alkali-rich porphyry may be formed in after the collision stage of India and Eurasia,after lithosphere shortened thickening,then thinning,result in the residual lithospheric Mantle and the thickening of the crust.partial melting.