苏皖地块——特提斯演化阶段独立的构造单元

SU-WAN BLOCK: AN INDEPENDENT TECTONIC UNIT DURING PERIOD OF TETHYAN EVOLUTION

基于苏皖地区的基底性质、晚元古代—中生代特征的沉积—火成建造、区域成矿和构造专属性 ,结合古地磁资料 ,提出了苏皖地块是特提斯演化阶段独立的构造单元的观点。它以苏鲁洋与华北克拉通间隔。震旦纪—早古生代的建造及变形特征与扬子克拉通有差异。石炭纪末和早二叠世的沉积和生物群表明它当时是古特提斯洋域里的一个中间地块 ,此时它已独立于扬子克拉通之外。三叠纪时苏鲁洋发生过大规模的消减但未闭合 ,因而苏皖地块的晚三叠世植物群与扬子克拉通有较明显区别。苏皖地块与华北克拉通 (指胶辽地块 )碰撞可能发生在早白垩世 ,该地区超高压变质岩的折返与之有关。之后 。

Based on the basement features, the unique sedimento-igneous formation and deformation of the Sinian Mesozoic, and the exclusive characters for regional mineralization and tectono thermal events, as well as the paleomagnetic data, the Su Wan (an abbreviation for Jiangsu and Anhui Provinces) Block might be considered as an independent tectonic unit during the period of Tethyan evolution The Su Lu (an abbreviation for Jiangsu and Shandong Provinces) Ocean, which once separated the Su Wan Block from the North China Craton, finally closed in Late Jurassic and Early Cretaceous, and the Su Lu Orogen was a part of the East Asian Yanshanides The Early Precambrian of the Su Wan Block might be a part of the North China Craton It drifted away, and correspondingly the Su Lu Ocean opened in Middle-Late Proterozoic The Su Wan Block attached to the Yangtze tectonic domain during the Sinian and Early Paleozoic, and its sedimento volcanic formation and deformation had some differences from that of the Yangtze Craton The global tectonic framework changed greatly from Devonian when the Paleotethyan oceanic basins opened Glacial activity and cold water faunas characterized the Gondwana in Permian, while a mantle plume recorded by eruption of the Emeishan basalt featured the Yangtze Craton During that time the Su Wan Block, not affected by the mantle plume, might be a median block in the Paleotethyan marine, which was evidenced by the sediments being affected by the glacial activity and the mixed faunas (although no cold water faunas discovered) In other words, The Su Wan Block must have been independent away from the Yangtze Craton since the latest Carboniferous The Su Lu Ocean once subducted in Triassic, but not closed, so the Late Triassic plant fossils in Su Wan Block differed from that of the Yangtze Craton The remained ocean subducted and closed in Late Jurassic and Early Cretaceous, indicated by the widely occurred Andean type arc magmatism From then on the Su Wan Block collided with the North China Craton and became a part of the embryonic Asia continent