关键词: 阿鲁科尔沁旗, 林西组, U-Pb同位素年龄, 晚二叠世晚期, 构造意义

Abstract: The Taohaiyingzi section at Aluke'erqin Qi, Inner Mongolia is one of typical Linxi Formation in north eastern China. The age
of the section is late Late Permian according to the newly discovered conchostracans, pollen, and spores. The Linxi Formation in
Taohaiyingzi consists mainly of black and gray-black sandstone and slate associations. The LA-ICP-MS U-Pb isotope analysis was
performed on zircons of the feldspar lithic sandstone from the 61st layer of the profile. The obtained concordant ages from 96 zircons and
the published 97 zircon data of clastic rocks from the first layer, amounting to a total of 193 detrital zircon data ages, were analyzed. The
193 detrital zircons can be divided into five groups according to age and frequency distribution characteristics: 248-302 Ma (n=80, ca.
41%) with peak ages at 263 Ma, 312-388 Ma (n=24, ca. 12%), 417-523 Ma (n=26, ca.13%), 564-991 Ma (n=38, ca. 20%), and 1000-2775 Ma
(n=25, ca.13% , 207Pb /206Pb age). The weighted average age for the youngest age group is 263±1.7 Ma (MSWD=1.7, n=80), which
coincided with the minimum peak age of 263 Ma. It was speculated that the maximum depositional age of the Linxi Formation is 263 Ma.
The detrital zircon age spectrum indicates the diversity and complexity of its sediment source. The main source should come from all
over the northeast and there is provenance information of North China plate and Siberian plate (1637±26 Ma, 1791±24 Ma, 1927±31 Ma,
1954 ±24 Ma, 2089 ±31 Ma, 2671 ±21 Ma, 2775 ±21 Ma). The peak age of the youngest group of detrital zircons obtained is 263 Ma,
indicating that the final closure between North China plate and Siberian plate occurred after Late Permian.

Key words: Alukerqin Qi, Linxi Formation, U-Pb isotopic age, the late Late Permian, tectonic significance