Magmatic and metamorphic events recorded in the gneisses of the Wenquan region, East Kunlun Mountains, Northwest China: Evidence from the zircon U-Pb geochronology

The geochronology of the detrital zircons of the eclogite-hosting paragneiss and granitic orthogneiss in the Wenquan region, eastern part of the East Kunlun Mountains was studied by using LA-ICP-MS method in this paper. The ages of the detrital zircons of the paragneiss vary in a range of 2400 similar to 430Ma, with a peak age value range from 2000Ma to 1200Ma, and minor metamorphic zircons of 1. 0 similar to 0. 9Ga (Neoproterozoic) and 430Ma (Early Paleozoic) also found, implying that the protolith of the paragneiss deposited from Late Mesoproterozoic to Early Neoproterozoic (Pt2-3) and underwere metamorphism in Early Neoproterozoic and Silurian. Zircons of the granitic orthogneiss yield magmatic crystallization ages at 900Ma, with epsilon(Hf)(t) values of zircons from one sample varying from -7. 0 to + 5. 5, but most of them showing negative values, and their t(DM) values from 1. 8Ga to 1. 3 Ga, demonstrating that the granites sourced mainly from the older basement melting (maybe metasediments from the Jinshuikou Group). The Neoproterozoic magmatic and metamorphic events should be related to the formation of global Rodinia supercontinent. Although only minor zircons of the paragneiss contain the information of an Early Paleozoic metamorphic event, we infer this gneiss experienced Early Paleozoic eclogite-fades metamorphism, linking that the paragneisses bearing the eclogite formed in Early Paleozoic (450 similar to 430Ma) as well as the in situ relationship between the gneiss and the eclogite, and tectonic evolution of HP-UHP belt in northern margin of the Qaidam Basin (QB). Base on similar tectonic histories of both the southern and northern margins of the QB, we speculate that the basement of the QB suffered Neoproterozoic and Early Paleozoic tectonic events, and the basement itself was not a stable craton scince Proterozoic.