苏皖地块构造演化、苏鲁造山带形成及其耦合的盆地发育

郯庐断裂带一度是古特提斯洋域中的转换断层,其东的苏皖地块和胶辽克拉通分别是曾经独立于扬子克拉通和华北克拉通之外的构造单元。苏皖地块原属中朝构造域,因中元古代时苏鲁洋的张开而向南漂移,震旦纪起归入华南构造域。受北东东-近东西向的江南断裂和江绍断裂右行走滑活动控制,苏皖地块及怀玉地块在石炭纪末-三叠纪时脱离华南构造域,成为古特提斯洋域中的中间地块。中国东部地区东亚燕山期山系的形成受两个地球动力学系统制约:一是苏鲁洋的消减及闭合后苏皖地块与胶辽克拉通的碰撞,二是江南断裂和江绍断裂的先剪后压,苏皖地块与拼合了的扬子-华北克拉通间发生斜向会聚和剪切造山,怀玉地块仰冲超叠在苏皖地块上。分5个阶段(印支期消减,早-中侏罗世斜向会聚,晚侏罗-早白垩世消减,早白垩世碰撞和燕山造山带坍塌)叙述了中生代造山作用的表现和特点,探讨了与各阶段造山作用耦合的盆地类型和时空分布。因燕山造山带的坍塌而燕山运动构建的“盆”“山”关系解脱,中国东部第三纪的伸展盆地直接叠加在燕山造山带的坍塌裂谷上。

TECTONIC EVOLUTION OF THE SU-WAN BLOCK, CREATION OF THE SU-LU OROGEN AND OROGENESIS-COUPLED BASIN DEVELOPING

The Tan Lu fault zone was once a transform fault in the Paleotethyan ocean, which separated the North China Craton and the Yangtze Craton to the west of the fault from the Jiao Liao (abbreviated from Shandong Liaoning) Craton and the Su Wan (abbreviated from Jiangsu Anhui) Block to the east of the fault. In other words, the latter two were tectonic units indenpendent of the North China and Yangtze Cratons respectively during the period of Tethyan evolution. The Su Wan Block was, originally, attached to the Sino Korea tectonic domain. The Su Lu (abbreviated from Jiangsu Shandong) Ocean opened in Middle Proterozoic, which accompanied with the Su Wan Block drifting far away from the Jiao Liao Craton, and turning over to the South China tectonic domain since Late Proterozoic. Controlled by the dextral strike slipping of the Jiangnan and Jiang Shao faults in strike of NEE WE, the Su Wan and Huaiyu Blocks became a median mass in the Paleotethyan ocean during the latest Carboniferous, Permian and Triassic, which was evidenced by the Early Permian Gondwana affinity or mixed Yangtze Gondwana fauna, the oxygen carbon isotopes influenced by the glacial activities in Gondwana, the Late Triassic phytocoenosis indicating a tropical subtropical environment, etc. The creation of the East Asian Yanshanides was constrained by two geodynamic systems. One was subduction and closure of the Su Lu ocean and followed continent continent collision of the Su Wan Block and the Jiao Liao Craton. Another was earlier shearing (left lateral) and later compression of the Jiangnan and Jiang Shao faults so that an oblique convergent and shear orogenesis occurred between the Su Wan Block and the amalgamated Yangtze North China Craton, and the Huaiyu Block obducted and overstacked the Su Wan Block. The Mesozoic orogenesis could be divided into five episodes, namely, the Indosinian subduction type orogenesis (the Nanxiang movement), the Early Middle Jurassic oblique convergent one (the Ningzhen movement), the Late Jurassic Early Cretaceous subduction and closure of the Su Lu Ocean, the Early Cretaceous collision and shearing orogeneses, and the orogen collapse in the latest Early Cretaceous and Late Cretaceous (the Maoshan movement). Every episode of Mesozoic orogenesis was evidenced by igneous activities, thrust or sliding thrust structures and unconformable contacts. The volcano sedimentary basin coupled every episode of Mesozoic orogenesis was illustrated, the tectonic settings, spatial temporal distributions and formation characters of the basins were concluded. The relation between orogenic movement and basin developing set up by the Yanshanian orogenesis was decoupled by a rapid collapse of the Yanshanides, and the Tertiary extensional basins in east China overlapped, directly, the collapse rifts of the Yanshanides, which was obviously different from the West China, where the coupling relation between orogenic movement and basin developing set up by the Indosian orogenensis was inherited during the Yanshanian period, and decoupled by the Himalayan orogenesis.