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

欧亚大陆包含几个古老的克拉通地块，它们被年轻的山脉带所干扰；后者约占欧亚大陆的一半。在过去的5亿年里，这些大型欧亚板块的运动和阿尔卑斯-喜马拉雅-印度尼西亚带的演化相对明确，而古生代山脉带的构造历史仍然是一个谜。乌拉尔-蒙古带是其中最大的也是最不为人所知的，它连接了北欧、西伯利亚、华北和塔里木地区。在哈萨克斯坦的中部，乌拉尔-蒙古带的宽度很大，由大约三个或更多的马蹄形、强烈弯曲的结构组成。这些构造中岩石的年龄从大约5.2亿年到2.8亿年不等，它们都代表着古岛弧，毫无疑问，这些岛弧是在俯冲带之上建立起来的，在俯冲带上，大型古代海洋域被再循环到地幔中。这些构造是如何在哈萨克斯坦乌拉尔-蒙古带组装的，以及这些组装是如何在欧亚大陆晚古生代大规模合并中发生的，如果能够确定其构造元素的优先空间分布，将有助于更好地理解。对构造内不同年龄的岩石进行详细的古地磁研究可以实现这一目标。目前正在收集来自哈萨克斯坦高度弧形构造不同部分的岩石，以便确定岛弧单元在其组装成构造之前和期间的纬度运动。哈萨克斯坦单元的这些运动可以与欧亚大陆组装期间周围北欧、西伯利亚和塔里木克拉通的运动进行比较。此外，该项目还将验证一个假设，即哈萨克斯坦强烈弯曲的结构是由原本几乎笔直的一系列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，南欧晚古生代山带和几个晚前寒武纪带（如阿拉伯和非洲东北部）与哈萨克斯坦有重要的相似之处。哈萨克斯坦地区的成功模式可以作为其他前中生代超大陆合并过程中吸积过程的有用模拟。

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.