Provenance of the Middle Permian Zhesi Formation in central Inner Mongolia, northern China: constraints from petrography, geochemistry and detrital zircon U-Pb geochronology

The exceptionally thick Middle Permian Zhesi Formation is considered key to understanding the late Palaeozoic tectonic setting of the North China-Mongolia segment of the Central Asian Orogenic Belt, yet its sedimentary environment and provenance remain ambiguous. An integrated approach incorporating detailed field observation and measurement, framework petrography, whole-rock geochemistry and detrital zircon U-Pb geochronology is applied here to investigate this problem. The framework petrography and whole-rock geochemical characteristics jointly suggest that the Zhesi Formation was derived primarily from felsic upper continental crust, with the source rocks undergoing intermediate weathering and short-distance transportation. Furthermore, the source rocks were composed of granites/granitoids that occurred in a transitional recycled orogen. LA-ICP-MS U-Pb detrital zircon data from sandstone samples show two main age groups of 480-410 and 290-265Ma. Accordingly, we deduce that the dominant provenance of the Zhesi Formation was northerly early to mid-Palaeozoic orogenic belt, late Palaeozoic granites/granitoids and volcanics, with a possible contribution from the Hunshandake Block. The subsiding depositional environment of this succession is in response to the Middle Permian extensional tectonic setting of the orogenic belt. Copyright (c) 2015 John Wiley & Sons, Ltd.