LA-ICP-MS U-Pb age of detrital zircons from Late Permian Linxi Formation in Ar Horqin Banner, Inner Mongolia

Abstract

The Taohaiyingzi geological section of the Linxi Formation in Ar Horqin Banner of Inner Mongolia is one of the typical sections in the north part of eastern China. The age of the section is late Late Permian according to the newly found conchostracans, pollen and spores. The Linxi Formation in Taohaiyingzi consists mainly of black and grayish black sandstone and slate association, with the sandstones being mainly feldspathic lithic rocks. Zircons from sandstone in the lower part of the section exhibit typical structures of magmatic genesis. LA-ICP-MS U-Pb dating of 96 zircons yielded six age populations: 248~301Ma (n=40, ca. 42%) with the peak age at 261Ma; 312~376Ma (n=12, ca. 13%) with the peak ages at 330Ma and 375Ma; 417~522Ma (n=14, ca. 15%) with the peak ages at 510Ma, 438Ma and 472Ma; 585~988Ma (n=18, ca. 19%) with the peak ages at 927Ma, 976Ma and 856Ma; the fifth group (n=7, ca. 7%) comprising 1091Ma, 1196Ma, 1198Ma, 1207Ma, 1368Ma, 1425Ma and 1548Ma; the sixth group (n=5,ca. 5%) comprising 1791Ma, 1927Ma, 1954Ma, 2089Ma and 2671Ma. On the basis of the youngest age peak 253Ma and the youngest discrete population of three zircons, of which the reliable ages are 248Ma±5Ma, 253Ma±5Ma, 254Ma±5Ma, the authors have come to the conclusion that the maximum depositional age of the Linxi Formation is 253Ma. The peak ages of 261Ma, 253Ma are consistent with the magmatic events of the collisional suturing and collage between the North China platform and the Siberia plate. This result and the biota fossils data from Linxi Formatiion provide reliable evidence that the continental collision between the northern margin of the North China plate and the Siberia plate culminated in the late Late Permian.