Petrogenesis of Granite Porphyry in Mariaicuo Area,Shuanghu County, Tibet,and Constraints on the Evolution in the Middle Section of Bangonghu-Nuj iang Suture Zone
Li Faqiao
Liu Zhibo
Tang Juxing
Song Yang
Gao Ke
Li Haifeng
Zhao Zhiqiang
Teng Lei
Abstract：LA-ICP-MS zircon U-Pb dating,geochemical and Sr-Nd-Pb isotopic data analysis were conducted on the granite por-phyry in Mariaicuo area in order to determine its formation time,petrogenesis,structural setting and geological significance. LA-ICP-MS zircon U-Pb dating of the granite porphyry in Mariaicuo yields a crystallization age of 78.3±0.4 Ma,indicating that the rock formed in the late of Late Cretaceous.Petrogeochemically,the samples of the rocks are high in SiO2 (72.41%—74.06%)and rich in Na2O+K2O of 6.66%—7.14%,which belong to calc-alkaline series.Its A/CNK ratios of 1.01—1.07 are of characteristics of weakly peraluminous granites.They are enriched in the large-ion lithospile elements of Rb, Ba,U,K and Th,and strongly depleted in high field strength elements Nb,Ta,P,and Ti.The REE distribution mode is obvious right-leaning,indicating that it remains garnet-amphibolite facies in source area.Their isotopic compositions are char-acterized by low initial(87 Sr/86Sr)iof 0.705 2—0.706 0 and low positiveεNd(t)(1.5—2.3)values and relatively young second-stage model age(tDM2=692—758 Ma)of crust.It has relatively homogeneous Pb isotope composition with the evolution of oro-genic characteristics.Comprehensive analysis shows that the granite porphyry in Mariaicuo area may originate from the new partial melting of crust within extensional background,and its source region is enriched in fluid and remains garnet-amphibolite facies,excluding plagioclase.It formed in the post-collision extensional environment,which occurred after the closure of Bangonghu-Nujiang Tethys Ocean(BTO)and collision between tarranes on both sides,when the middle section of Bangonghu-Nujiang suture zone has entered the extension phase in Late Cretaceous.
Keywords：petrogenesispost-collisiongranite porphyryMariaicuo areamiddle section of Bangonghu-Nujiang suture zonepetrology
Publication Date：2018-01-01
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：19( 1051-1069 )