试论郯城—庐江断裂带的形成、演化及其性质

郯(城-)庐(江)断裂带由前白垩纪的3条重要的边界断裂连接而成:古郯庐断裂曾是连接秦岭—大别洋与苏鲁洋的转换断层,辽渤断裂是华北克拉通与胶辽克拉通之间的分界,敦化—密山断裂则是西伯利亚次大陆与一系列拼贴的外来(移置)地体间的分界。早白垩世,随亚洲大陆雏形的出现,郯庐断裂带形成并扩大其规模(如包括了依兰—伊通断裂)。江西的赣江断裂和鄂东南湘东北的团(风-)麻(城)断裂白垩纪时与郯庐断裂有相同的活动方式,可视为郯庐断裂带的南延。从本质上说,郯庐断裂带是一条斜向(左行)汇聚—剪切造山带,这一造山作用在中生代里是一个连续的分阶段进行的过程,左行走滑活动始自三叠纪,至早白垩世造山带形成,始于早白垩世晚期并于晚白垩世达到全盛的张裂活动则是造山带坍塌的反映。新生代起东亚地区进入新的地史阶段,郯庐断裂带进入消亡期,更新世时已明显解体为活动方式各不相同的若干段。文章还简要讨论了古郯庐断裂的形成时代、印支期走滑活动的性质和东亚大陆边缘地区的构造格架等问题。

AN APPROACH TO THE TANCHENG-LUJIANG FAULT ZONE:ITS CREATION, EVOLUTION AND CHARACTER

The Asian continent is a composite one, in which a large-scale shear zone might be, generally, created by connection of some boundary fractures of microcontinents. The predecessor of the Tan(cheng)-Lu(jiang) fault zone in eastern Asia was composed of three boundary fractures. The Paleo-Tan-Lu fault in the Tethyan domain was a transform fault connecting the Qinling-Dabie and the Su-Lu oceans, the former closed in the Indosinian orogeny and the latter in the Yanshanian orogeny respectively. The Liao(ning)-Bo(hai) fault, which might be related to the transform system in the Paleo-Asian(or Paleo-Mongolian) oceanic domain, was a demarcation between the North China and the Jiao-Liao microcontinents. The Dunhua-Mishan fault in NE China was a boundary of a series of allochthonous terranes accreated during Mesozoic, for example, the Xingkai, the Nadanhada-Bijin and the Central Sikhote-Alin terranes. Following the closure of the Su-Lu and the Mongolia-Ochotsk oceanic basins in Late Jurasic, an embryonic form of the Asian continent created in Early Cretaceous, on which the Tan-Lu fault zone appeared by connecting of the Paleo-Tan-Lu, the Liao-Bo and the Dunhua-Mishan faults. In addition, some pre-Cretaceous intra-continental(intra-plate) fractures, such as the Yilan-Yitong, the Ganjiang and the Tuan(feng)-Ma(cheng) faults, were evolved into the Tan-Lu fault zone in Cretaceous. As concerns the character of the Tan-Lu fault, there once existed two main opinions: a sinistral wrench fault, or a continental rift. The paper represented that the Tan-Lu fault zone was, in essential, an oblique (sinistral) convergence-shearing orogen, which should be third-type interplate orogen juxtaposed the subduction-type and collision-type orogens. The oblique convergence-shearing orogeny occurred along the Paleo-Tan-Lu fault by stages during Mesozoic, with the first stage being the Indosinian orogeny. The Tan-Lu oblique convergence-shearing orogen finalized the design in Early Cretaceous, and the Yanshanian orogens in East Asia collapsed in Late Cretaceous. Since the sinistral orogeny migrated northwards, the collapse-related rifting had such a tendency: earlier in the south and later in the north. The Tan-Lu fault zone entered its period of disintegration during Cenozoic. Owing to varied velocity and extent of the Asiam continent creeping to the Pacific ocean, and the local tectonic stress fields occurring, each sector of the former Tan-Lu fault zone displayed different developing, for example, the Ganjiang and Liao-Bo faults being normal faulting in Pleistocene, while the northern Anhui sector of the Tan-Lu faultt being a situation of compression.