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

合作研究：蒙古东戈壁断裂带走滑历史：板内变形模式、沉积盆地演化和区域断裂联系

• 批准号: 0929902
• 负责人: Laura Webb
• 金额: --
• 依托单位: University of Vermont & State Agricultural College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-25 至 2011-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0929902&HistoricalAwards=false
• 关键词: Collaborative; Research; Strike; Slip; History

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.

这项研究有助于了解大陆如何因大陆碰撞等重大构造事件而变形。亚洲大陆是解决以下问题的天然实验室：亚洲内陆地区如何因印度和亚洲的碰撞而发生变形？随着时间的推移，变形模式如何以及为何会发生变化？沉积记录如何反映此类事件？该项目采用构造地质学、地质年代学和沉积盆地分析工具来重建蒙古东戈壁断裂带沿线的位移历史和沉积盆地演化。初步数据表明，自晚古生代以来，这一主要的陆内剪切带至少被重新激活了四次；这项工作记录了两个最不受约束的左侧滑移事件（中生代早期和新生代早期）。由于蒙古东南部的数据缺乏，东戈壁断裂带本质上被当作亚洲构造“拼贴”演化模型的通配符。例如，已发表的模型引用了未经现场测试的区域地图关系，估计左旋偏移量范围从大约 200 公里的早期中生代滑移到大约 400 公里的纯新生代滑移。后一种解释暗示了阿尔金塔格断层与假设的（但尚未有大量记录的）走滑断层之间存在前中新世联系，该断层穿过蒙古东南部延伸至鄂霍次克海。本研究通过在东戈壁断裂带已建立新生代走滑断层的控制点西南方向的中蒙边境地区附近测绘，测试了这种运动联系是否成立，并提供了第一个对时间的现场和分析约束。和滑移幅度。这些结果通过检验东戈壁断裂带重新激活古生代缝合带的假设，进一步证实了有利于剪切带启动和重新激活的机制。收集地质年代数据来评估蒙古东南部板内变形的时间，作为远场力和不断变化的边界条件的函数。因此，这项研究与亚洲中生代至近代碰撞史上的大陆块挤压和连续缩短模型有关。东戈壁断裂带暴露的多种构造水平和变形所涉及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，对东戈壁断裂带变形阶段与东戈壁地区沉积岩之间关系的研究限制了扳手构造背景下“多历史”沉积盆地的起始、地层发育和随后的分裂机制。此次合作的多学科性质凸显了整合不同地质数据集来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地球上一个未被充分研究且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，还有两名博士学位。来自犹他州和雪城大学的学生和本科生参与了该研究的各个方面，并接受了使用技术解决科学问题的培训。该项目由构造学计划和东亚太平洋小组提供支持。国际科学与工程。