Zircon and monazite U-Pb geochronology and trace elements unravel a Paleoproterozoic volcanic-sedimentary metamorphic type rare earth element deposit in NE China

Reported Paleoproterozoic rare earth element (REE) deposits worldwide are quite limited. Here, we present the first detailed studies on a volcanic-sedimentary metamorphic type REE deposit, namely the Shengtieling REE deposit in NE China, to give a further case. The Shengtieling REE deposit (central Liaoning) occurs in the Lieryu Formation of the South Liaohe Group and is located in the Paleoproterozoic Jiao-Liao-Ji tectonic belt. The BSE images, combined with the monazite LA-ICP-MS in-situ trace elements, show that the main REE minerals are monazite, xenotime, and apatite from the magnetite leptynite. According to zircon and monazite U-Pb geochronological results, the maximum depositional age for magmatic clastic zircon is 1.95Ga, but both metamorphic zircons and monazites give similar ages of 1.90~1.87Ga. Whole-rock trace elements data suggest a continental island arc origin for the magnetite leptynite samples, thus indicating that the protolith may be arc-related sedimentary rocks. Notably, the 1.90~1.87Ga metamorphism is consistent with the timing of regional metamorphism, confirming the existence of arc-continent collision during the formation of the Jiao-Liao-Ji tectonic belt. Thus, based on the above new results, the Shengtieling REE deposit should be a typical Paleoproterozoic volcanic-sedimentary metamorphic type REE deposit. More attention should be paid to exploring similar REE deposit types in NE China and elsewhere.