Permian radiolarians from the Engeerwusu suture zone in Alxa area of Inner Mongolia and its geological significance

Details of Permian albaillellarians from the exotic siliceous blocks within the Engeerwusu ophiolitic mélange along the Engeerwusu suture zone are presented for the first time. Among them, seven species belonging to three genera were systemically investigated. Most species recorded can be correlated with the Permian radiolarian zones in Japan and the USA. Two radiolarian assemblages were distinguished, indicative of Early Permian and late Middle to early Late Permian respectively. On the basis of the deep-water settings indicated by the albaillellarian fauna, the radiolarians extracted from the exotic siliceous blocks within the Engeerwusu ophiolitic mélange along the Engeerwusu suture zone may provide new evidence for the tectonic evolution of the Engeerwusu suture zone between the North China Plate and the Tarim Plate. According to the deep-water setting indicated by the latest radiolarian assemblage of late Middle-early Late Permian epoch, the authors hold that an ocean existed between the North China Plate and the Tarim Plate during late Middle to early Late Permian, and the closure of the ocean between the North China Plate and the Tarim Plate might have occurred during late Late Permian period.