Hf(t)values(-19.3to-2.5),suggesting that their magmatic host rocks resulted from partial melting of theenriched mantle or ancient crustal materials.Combined with previous studies,we propose that the LateDevonian-Early Carboniferous magmatic rocks in the Lhasa terrane probably formed in an arc-back-arcsystem which resulted from the southward subduction of the Paleo-Tethys oceanic crust.The back-arc basindeveloped as the Sumdo Paleo-Tethys ocean,which began to shrink as oceanic crust subducted northwardsunderneath the North Lhasa terrane during the Late Carboniferous-Permian and finally closed during theTriassic.?The Late Paleozoic tectonic evolution of the Lhasa terrane remains poorly understood due to thepaucity of the Late Paleozoic magmatic rocks exposed at the surface.Detrital zircons in the sedimentary rockscan provide arecord of magmatic rocks that have been eroded.Here we report detrital zircon U-Pb ages,trace-element and Hf isotopic data of metasedimentary rocks from the Nyingchi Complex in the easternHimalayan syntaxis.Detrital zircons from the metasedimentary rocks yield major age populations of330-364Ma,490-800Ma,1000-1200Ma,and1500-1800Ma.The weighted mean ages of the youngest three detritalzircons indicate Carboniferous(~330Ma)depositional age for their sedimentary protoliths.Provenanceanalysis indicates that the sedimentary detritus was sourced from the Lhasa terrane itself.The presence ofabundant330-364Ma detrital zircons indicates that the Lhasa terrane was characterized by LateDevonian-Early Carboniferous magmatism.The trace-element compositions of the330-364Ma detrital zirconsindicate that their magmatic host rocks mainly include mafic rocks and granitoids,and minor carbonatite.Some mafic host rocks probably formed in rift-related tectonic setting,and the others formed in arc-relatedtectonic settings.The granitic host rocks were S-type granites.
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