Muscovite 40Ar/39Ar dating of the Palaeoproterozoic granitoid gneiss in the Zhongtiao Mountains and its geological significance

The Zhongtiao Mountains as one of the significant components of the Trans-North China Orogen, located in the southernmost part of Shanxi Province, comprise a basement of the Sushui Complex, Jiangxian Group, Zhongtiao Group, and a cover of Danshanshi Group dominated by conglomerate, and Xiyanghe and Ruyang Groups, separated from each other by unconformities and tectonic contact. The metamorphic rocks in the Zhongtiao Mountains are of vital importance in understanding the Precambrian tectonics and evolution of the North China Craton. However, the time of metamorphism so far is still poorly constrained. Herein, we present laser and conventionally 40Ar/39Ar analyses on fabric-forming metamorphic muscovite from a Palaeoproterozoic granitoid gneiss from the Sushui Complex in the Zhongtiao Mountains. The laser 40Ar/39Ar dating returned an isochron age of 1830Ma±20Ma, and the conventionally 40Ar/39Ar data yield a plateau age of 1852Ma±11Ma, which can be considered as minimum and optimal estimates of the muscovite argon closure temperature age, respectively. Furthermore, the plateau age of 1852Ma±11Ma is in excellent agreement with published U-Th-Pb Electron microprobe monazite prominent peak age, indicating that metamorphic muscovite recorded a late Palaeoproterozoic metamorphic event. Those metamorphic ages are also consistent with the metamorphic and deformation events occurred in the Huai'An-Lüliang-Hengshan-Wutai-Zanhuang regions of the Trans-North China Orogen, revealing that the Eastern and Western blocks of the North China Craton was stitched together along the Trans-North China Orogen at late Palaeoproterozoic, but not Neoarchean.