Provenance analysis of Permian sandstones in the central and southern Da Xing'an Mountains, China: Constraints on the evolution of the eastern segment of the Central Asian Orogenic Belt

摘要

Modal, chemical and U-Pb zircon data from Permian sandstones in the central and southern Da Xing'an Mountains (eastern Inner Mongolia, China) constrain, for the first time, plate collision processes between the northern margin of the North China craton and the composite Erguna-Xing'an-Songliao block. The study area is located between the Ondor Sum-Xar Moron and Hegenshan suture zones of the eastern segment of the Central Asian Orogenic Belt. Modal and geochemical analyses of Permian sandstones suggest derivation from dissected continental arc and recycled orogenic sources. LA-ICP-MS U-Pb detrital zircon data from sandstones indicate Early Permian to earliest Triassic maximum depositional ages (278±4. Ma to 249±3. Ma). These data also show two uniform age groups of 270-280. Ma and 310-320. Ma, and we interpret their source to be mainly the Sonidzuoqi-Xilinhot-southern Xi Ujimqin magmatic arc in the north (the southern margin of the Xing'an-Erguna block). The sample from the Upper Permian to lowermost Triassic Linxi Formation in the Linxi area also contains zircons with age groups of ~. 1800. Ma and ~. 2500. Ma, consistent with derivation from the northern margin of the North China craton, which lies to the south. Therefore, the collision between the North China craton and the Xing'an-Erguna block began during the deposition of the Linxi Formation, and the final closure of the intervening oceanic basin occurred during ca. Late Permian-earliest Triassic times, forming the Ondor Sum-Xar Moron suture zone.