Detrital zircon U-Pb dating of Nanhua meta-tuffite in South Jiangxi and constraint on the time limit of the rift basin

Ion-adsorption type REE deposits is hosted in regolith of Neoproterozoic epimetamorphic rocks in South Jiangxi, China. LA-ICP-MS U-Pb dating of detrital zircons from two metamorphic tuff samples of the originally identified Kuli Formation of Qingbaikou System in a mine area yielded the harmonic ages of 88 groups and 110 groups respectively. They are predominantly Neoproterozoic and have ages ranging from 810 to 667 Ma with three age peaks at ca 798 Ma (n=55), 737 Ma (n=127) and 680 Ma (n=6). There are also a few Meso-to Paleoproterozoic zircon grains with ages scattering from 2.85 Ga to 1.08 Ga. The dating results probably suggest that the sedimentary age of the tuffite may be Nanhua Period. It is speculated that the provenance may be volcanic-sedimentary rocks of late Qingbaikou Period to Nanhua Period in the eastern part of Jiangnan orogenic belt (northeast Jiangxi-southern Anhui-western Zhejiang). The super thick marine volcanic-clastic sediments of the same period in southern Jiangxi might be formed in the rift basin after the breakup of the ancient continent of South China, and the sedimentary time of the secondary rift basin in southern Jiangxi is about 810-727 Ma.