内蒙古阿拉善地区恩格尔乌苏缝合带二叠纪放射虫及其地质意义

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

报道了采自恩格尔乌苏缝合带的蛇绿混杂岩硅质外来岩块中的二叠纪阿尔拜虫目放射虫化石,包括3属7种,可以划分为2个放射虫化石组合,能够与日本、美国的放射虫化石带进行对比,其地质时代分别为早二叠世和中二叠世晚期—晚二叠世早期。恩格尔乌苏缝合带位于华北板块和塔里木板块之间,这些放射虫化石的发现为研究恩格尔乌苏缝合带的构造演化提供了新的证据。鉴于其中最新的放射虫组合的地质时代为中二叠世晚期—晚二叠世早期,认为华北板块与塔里木板块之间自中二叠世晚期—晚二叠世早期曾经存在古海洋,即华北板块和塔里木板块的拼合时间是晚二叠世晚期。

Details of Permian albaillellarians from the exotic siliceous blocks within the Engeerwusu ophiolitic melange along the Eng-eerwusu suture zone are presented for the first time. Among them, seven species belonging to three genera were systemically investi-gated. 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 ophiol-itic melange 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 assem-blage 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.