Discovery of khondalite series from the western segment of Altyn Tagh and their petrological and geochronological studies

• Published in: Science China. Earth sciences 2000-06, Vol.43 (3), p.308-316
• Main Authors: Zhang, Jianxin, Zhang, Zeming, Xu, Zhiqin, Yang, Jingsui, Cui, Junwen
• Format: Article
• Language: English
• Subjects: Aluminium; Aluminum; Basalt; Biotite; Continental margins; Dating; Garnet; Garnets; Geochemistry; Geochronology; Geology; Gneiss; Lead; Metamorphism; Metamorphism (geology); Petrology; Radiometric dating; Schist; Schists; Sedimentary facies; Sedimentary rocks; Segments; Sillimanite
• ISSN: 1674-7313; 1869-1897
• DOI: 10.1007/BF02906827

The khondalite series, which are characterized by aluminum-rich gneisses (schists) consisting of sillimanite-garnet-biotite-monzonite gneiss, garnet-biotite-monzonite gneiss, graphite-sillimanite-biotite schist, and garnet-amphibole two-pyroxene granulites occurring as lenses and layers within gneisses (schists), were discovered in Tula area of western segment of Altyn Tagh. The petrology and geochemistry indicate that the protoliths of aluminum-rich gneisses (schists) are aluminum-rich pelitic and pelitic arenaceous sedimentary rocks, the protoliths of basic granulites are continental tholeiitic basalts. Therefore, the khondalite series may be produced at continental margin. They had suffered granulitic facies metamorphism with peak temperatures of 700–850°C and pressures of 0.8–1.2 GPa. The U-Pb and Pb-Pb isotopic dating of zircons provided the ages of 447–462 Ma representing the ages of peak granulitic metamorphism. The U-Pb dating of detrital zircons from aluminum-rich gneisses yielded older upper intercept ages which reflect the times of older materials derived from source rocks of the gneiss protoliths.