Building the Eurasian Supercontinent: Paleomagnetic Study of Kazakhstan to Assess its Role in Uniting Baltica with Siberia

欧亚大陆包含几个较古老的板块，它们由介于其间的较年轻的山脉带连接在一起;后者约占欧亚大陆的一半。尽管这些大型欧亚大陆块体在过去5亿年中的运动以及阿尔卑斯-喜马拉雅-印度尼西亚带的演化相对明确，但古生代山脉带的构造历史仍然是个谜。其中最大但最不为人所知的是乌拉尔-蒙古带，它将北欧、西伯利亚、华北和塔里木地块联合起来。 在哈萨克斯坦的中部，乌拉尔-蒙古带的宽度很大，由三个或更多马蹄形的强烈弯曲结构组成。 这些结构中的岩石年龄范围从大约5.2亿到大约2.8亿年前，都代表着古老的岛弧，毫无疑问，这些岛弧是在俯冲带之上建造的，在俯冲带中，大型的古代海洋域被回收到地幔中。 这些结构如何成为组装在哈萨克斯坦的乌拉尔-蒙古带，以及如何在大规模的晚古生代欧亚大陆的融合组装发生可以变得更好地理解，如果可以确定其构造元素的空间分布。 对构造内不同年龄岩石的详细古地磁研究能够实现这一目标。 正在收集哈萨克斯坦高弧形构造不同部分的岩石，以确定岛弧单元在组装成构造之前和组装期间的纬向运动。 哈萨克斯坦单元的运动可以与欧亚大陆拼合过程中周围的北方欧洲、西伯利亚和塔里木盆地的运动相比较。 此外，该项目还将检验一种假设，即哈萨克斯坦强烈弯曲的结构是由一系列原本几乎笔直的岛弧大规模弯曲造成的。在最广泛的地质意义上，值得注意的是，南欧晚古生代山脉带和几个晚前寒武纪带（例如，在阿拉伯和非洲东北部）显示出与哈萨克斯坦重要的相似之处。 哈萨克斯坦域的一个成功的模型可以作为一个有用的模拟其他前中生代吸积过程中合并的超大陆。

Eurasia contains several older cratonic blocks that are united by intervening younger mountain belts; the latter account for about half of the Eurasian landmass. Whereas the motions during the last 500 million years of these large Eurasian blocks and the evolution of the Alpine-Himalayan-Indonesian belt are relatively well defined, the tectonic history of the Paleozoic mountain belts remains enigmatic. One of the largest and least understood is the Ural-Mongol belt, which unites the North-European, Siberian, North China, and Tarim blocks. In its central part in Kazakhstan, the Ural-Mongol belt attains great width and consists of a nest of some three or more horseshoe-shaped, strongly curved structures. The ages of the rocks in these structures range from about 520 to about 280 million years ago, and all represent ancient island-arcs, which undoubtedly were built above subduction zones where large ancient oceanic domains were recycled into the Earth's mantle. How these structures became assembled in the Ural-Mongol belt of Kazakhstan and how this assembly occurred within the large-scale late Paleozoic amalgamation of Eurasia can become better understood if the prior spatial distribution of its tectonic elements can be determined. Detailed paleomagnetic studies on rocks of varying ages within the structures are able to achieve this goal. Rocks from different parts of the highly arcuate structures in Kazakhstan are being collected in order to determine the latitudinal motions of the island-arc units prior to and during their assembly into the structures. These motions of Kazakhstan units can then be compared with the motions of the surrounding cratons of Northern Europe, Siberia and Tarim during the assembly of Eurasia. In addition the project will test the hypothesis that the strongly curved structure of Kazakhstan resulted from large-scale bending of an originally nearly straight series of island arcs. In the broadest geological sense, it is noteworthy that the late Paleozoic mountain belt of southern Europe and several late Precambrian belts (e.g., in Arabia and northeast Africa) show important similarities with Kazakhstan. A successful model for the Kazakhstan domain may serve as a useful analog for other pre-Mesozoic accretion processes during the amalgamation of supercontinents.