Collaborative Research: Strike-Slip History of the East Gobi Fault Zone, Mongolia: Modes of Intraplate Deformation, Sedimentary Basin Evolution, and Regional Fault Linkages

这项研究有助于了解大陆如何变形，以应对重大的构造事件，如大陆-大陆碰撞。亚洲大陆是一个天然的实验室，可以解决诸如以下问题：亚洲内部如何因印度和亚洲的碰撞而变形？变形模式是如何以及为什么会随着时间而改变的？沉积记录如何反映这些事件？本项目利用构造地质学、年代学和沉积盆地分析等工具，重建了蒙古国东戈壁断裂带沿着的位移历史和沉积盆地演化。初步数据表明，这一主要的陆内剪切带被重新激活至少四次，因为晚古生代，这项工作的文件中的两个最小的约束情节的左行滑动（早中生代和早新生代）。由于缺乏蒙古东南部的资料，东戈壁断裂带基本上被用作亚洲构造“拼贴”演化模式的一个替代品。“例如，已发表的模型估计左侧偏移范围从大约200公里的中生代早期滑动到大约400公里的纯新生代滑动，引用尚未经过实地测试的区域地图关系。后一种解释意味着前中新世之间的联系阿尔金断层和假设-但在很大程度上还没有记录-走滑断层延伸通过蒙古东南部鄂霍次克海。本研究测试是否允许这种运动学联系通过映射附近的中蒙边境地区，西南部的控制网站，新生代走滑断层已建立在东戈壁断裂带，并提供了第一个字段和分析的时间和规模的限制。这些结果承担进一步的机制有利于启动和复活的剪切带通过测试的假设，东戈壁断裂带复活古生代缝合线。地质年代学数据的收集，以评估蒙古东南部的板内变形的时间作为远场力和不断变化的边界条件的函数。因此，这项研究是相关的大陆块体挤压和连续体缩短模型在亚洲的碰撞历史从中生代到最近。东戈壁断裂带暴露的各种构造层次和涉及变形的岩性为研究上地壳和深部剪切带/断裂带发育的流变控制提供了极好的机会。此外，东戈壁断裂带的变形阶段和沉积岩在东戈壁地区之间的关系的调查约束机制的启动，地层发展，并随后肢解的“多历史”沉积盆地在扭构造环境。合作的多学科性质突出了整合不同地质数据集以解决一系列复杂问题的力量。这项研究的结果有助于更好地了解我们星球上一个研究不足和矿产资源丰富的地区。这项工作的国际性质促进了蒙古和美国地质学家之间的合作，其中包括两名早期职业女性调查员。此外，两名博士来自犹他州和锡拉丘兹的学生和本科生参与了研究的各个方面，并接受了使用技术解决科学问题的培训。2该项目由构造计划和国际科学与工程办公室的东亚和太平洋小组提供支持。

This research contributes to the understanding of how continents deform in response to major tectonic events such as continent--continent collisions. The continent of Asia is a natural laboratory to address questions such as: How has the interior of Asia deformed in response to the collision of India and Asia? How and why might the modes of deformation have changed over time? How does the sedimentary record reflect such events? This project employs tools of structural geology, geochronology, and sedimentary basin analysis to reconstruct displacement history and sedimentary basin evolution along the East Gobi Fault Zone, Mongolia. Preliminary data suggest that this major intracontinental shear zone was reactivated at least four times since the late Paleozoic; this work documents two of the least-constrained episodes of left-lateral slip (early Mesozoic and early Cenozoic). Due to paucity of data from southeastern Mongolia, the East Gobi Fault Zone is essentially played as a wildcard against models of evolution of the Asian tectonic "collage." For example, published models estimate left-lateral offset ranging from approximately 200 km of early Mesozoic slip to approximately 400 km of purely Cenozoic slip, citing regional map relations that have not been field-tested. The latter interpretation implies a pre-Miocene linkage between the Altyn Tagh fault and hypothesized--but as yet largely undocumented--strike-slip faults extending through southeastern Mongolia to the Sea of Okhotsk. This study tests whether this kinematic linkage is permissible via mapping near the China-Mongolia border zone, southwest from control sites where Cenozoic strike-slip faulting has been established in the East Gobi Fault Zone, and provides the first field and analytical constraints on the timing and magnitude of slip. These results bear further on mechanisms favoring initiation and reactivation of shear zones by testing the hypothesis that the East Gobi Fault Zone reactivates a Paleozoic suture. Geochronologic data are collected to evaluate the timing of intraplate deformation in southeastern Mongolia as a function of far field forces and evolving boundary conditions. Thus, this research is relevant to models of continental block extrusion and continuum shortening during Asia's history of collisions from Mesozoic-Recent. The great variety of structural levels exposed and lithologies involved in deformation in the East Gobi Fault Zone provide an excellent opportunity to investigate rheologic controls on shear zone/fault zone development in the upper crust and at depth. Furthermore, investigation of the relationship between deformational phases of the East Gobi Fault Zone and sedimentary rocks in the East Gobi region constrain mechanisms of initiation, stratigraphic development, and subsequent dismembering of "poly-history" sedimentary basins in wrench-tectonic settings. The multidisciplinary nature of the collaboration highlights the power of integration of diverse geologic datasets to address a complex set of questions. Results of this study contribute to the greater understanding of an understudied and mineral resource-rich region of our planet. The international nature of this work fosters collaboration between Mongolian and American geologists, including two early-career female investigators. Additionally, two Ph.D. students and undergraduate students from Utah and Syracuse participate in all aspects of the study and are trained in the use of technology to solve scientific problems.Support for the project is provided by the Tectonics Program and by the East Asia and Pacific Group of the Office of International Science and Engineering.