Collaborative Research: From subduction to suture: testing collisional stage and lithospheric strength as controls on orogenic structure in the Caucasus

合作研究：从俯冲到缝合：测试碰撞阶段和岩石圈强度作为高加索造山结构的控制

• 批准号: 2050618
• 负责人: Nathan Niemi
• 金额: $ 42.48万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2050618&HistoricalAwards=false
• 关键词: Collaborative; Research; subduction; suture; testing

Mountain belts form where two plates that make up the outer-most shell of the Earth (the crust) collide. These collisions are driven by the plate tectonic cycle. Where one colliding plate is composed of dense oceanic crust and the other is more buoyant continental crust, which makes up most of the landmasses on Earth, the oceanic crust sinks back in the Earth’s deep interior via subduction to recycle material from the surface back into Earth’s mantle. However, when the two colliding plates are composed of continental crust, they both resist subduction, resulting in the formation of the largest mountain belts on Earth. The collisions that form these mountain belts produce devastating earthquakes, concentrate natural resources, and drive biological evolution via the rapid growth/decay of topography. Continental collisions often terminate periods of oceanic plate subduction, but much is still not understood about the transition between these two processes, including how a subduction zone converts to a continental collision to produce a mountain chain, what controls the size and locations of large earthquakes, or what modulates the distribution of economically critical ores. This 3-year, international collaboration between researchers at the University of California, Davis, the University of Michigan, and Ilia State University in the Republic of Georgia will investigate the transition from subduction to continental collision in the Greater Caucasus Mountains, a major tectonic element of the Arabia-Eurasia continental collision, and one of the only places Earth where this transition can be observed today. This project will advance scientific knowledge and contribute to society by training PhD students, which contributes to the preparation of a globally competitive STEM workforce and expands the pool of STEM educators. The project will engage and mentor undergraduate students who are from underrepresented minorities, providing professional development and increased participation in STEM, and will increase domestic and international partnerships by engaging US students in collaborative, international work, providing training to graduate students from Ilia State University, deepening collaborations between US and Georgian researchers, and supporting new research collaborations within the US. Finally, this project will enhance research and educational infrastructure by supporting analytical capacities at US research universities.The transition from oceanic subduction to continental collision defines a profound change in force balance and dynamics along the plate boundary. Thus, determining the spatial and temporal distribution of strain during the transition from subduction to collision is critical for relating the deformational response of the orogen to the far-field plate motions driving that deformation. During the transition, buoyant crust of the subducting continental margin enters the trench, reduces the dip of the subduction megathrust, increases plate-boundary coupling, and deforms the overriding plate. The transition from subduction to collision triggers fundamental changes in the spatial distribution and rates of deformation, exhumation, and deposition along the convergent margin as the accretionary wedge evolves into the suture between colliding continental blocks. Geologic observations of the spatial and temporal patterns of deformation during the transition from subduction to collision within an active continental collision zone remain highly elusive, primarily because of a paucity of localities to study this transition. This project will test the idea that the Greater Caucasus serve as a natural laboratory to study the subduction to collision transition by determining if a fundamental along-strike dichotomy in the geology, structure, seismicity, and geodetic shortening results from a transition from active subduction in the eastern part of the range to continental collision and terminal suturing in the west. Specifically, this project will test the hypothesis that there is a terminal suture in the Greater Caucasus, west of ~45°E longitude, that represents a now-subducted oceanic back-arc basin that formerly separated Eurasia to the north from a continental ribbon to the south. East of 45°E, collision has not yet occurred, and the range is dominated by active oceanic subduction. The project has two goals: (1) To illuminate the geologic observations necessary to recognize suturing in ancient continental collisions by describing and quantifying the geologic expression, duration, kinematics, and mechanics of this fundamental change in dynamic state and (2) to capture the deformational response of an orogen to the evolving shift in plate boundary forces associated with the transition from subduction to collision, and thus quantify the relative roles of plate strength and plate boundary coupling in controlling orogenic structure.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

构成地球最外层外壳（地壳）的两个板块碰撞时形成了山脉带，这些碰撞是由板块构造循环驱动的，其中一个碰撞板块由致密的海洋地壳组成，另一个则由浮力较大的大陆地壳组成。地壳构成了地球上的大部分陆地，海洋地壳通过俯冲作用沉回到地球内部深处，将地表物质回收到地幔中。然而，当两者碰撞时。板块由大陆地壳组成，它们都抵抗俯冲，从而形成了地球上最大的山脉产生带，形成这些山脉带的碰撞会引发毁灭性的地震，集中自然资源，并通过快速生长/衰退来驱动生物进化。地形通常会终止海洋板块俯冲时期，但人们对这两个过程之间的过渡仍知之甚少，包括俯冲带如何转变为大陆碰撞以产生山脉，是什么控制了大洋板块的大小和位置。地震，加州大学戴维斯分校、密歇根大学和乔治亚州伊利亚州立大学的研究人员之间为期三年的国际合作将研究从俯冲到大陆碰撞的转变。位于大高加索山脉，这是阿拉伯-欧亚大陆碰撞的主要构造要素，也是当今地球上唯一可以观察到这种转变的地方之一。该项目将通过培训博士生来推进科学知识并为社会做出贡献。到培养具有全球竞争力的 STEM 劳动力并扩大 STEM 教育工作者队伍。该项目将吸引和指导来自代表性不足的少数族裔的本科生，提供专业发展并增加对 STEM 的参与，并将通过吸引美国学生来加强国内和国际合作伙伴关系。合作的国际工作，为伊利亚州立大学的研究生提供培训，深化美国和格鲁吉亚研究人员之间的合作，并支持美国境内的新研究合作。最后，该项目将通过支持美国研究的分析能力来加强研究和教育基础设施。大学的转变海洋俯冲到大陆碰撞定义了沿板块边界的力平衡和动力学的深刻变化，因此，确定从俯冲到碰撞过渡期间应变的空间和时间分布对于将造山带的变形响应联系起来至关重要。在转变过程中，俯冲大陆边缘的浮力地壳进入海沟，减少了俯冲巨型逆冲断层的倾角，增加了板块边界耦合，并使上覆板块变形。随着增生楔演变成碰撞大陆块之间的缝合线，从俯冲到碰撞的转变引发了沿汇聚边缘的变形、折返和沉积的空间分布和速率的根本变化。活跃大陆碰撞带内从俯冲到碰撞的转变仍然非常难以捉摸，主要是因为很少有地方研究这种转变，该项目将检验大高加索地区作为一个大陆碰撞带的想法。自然实验室，通过确定地质、结构、地震活动和大地缩短中的基本沿走向二分法是否是从山脉东部的主动俯冲到大陆碰撞和终端缝合的过渡来研究俯冲到碰撞过渡的自然实验室具体来说，该项目将检验大高加索地区东经约 45°以西存在一条终端缝合线的假设，该缝合线代表了一个现已俯冲的海洋弧后盆地，该盆地以前是分离的。从欧亚大陆以北到东经45°以东，碰撞尚未发生，该范围以活跃的海洋俯冲为主。该项目有两个目标：（1）阐明必要的地质观测。通过描述和量化这种动态根本变化的地质表现、持续时间、运动学和力学来认识古代大陆碰撞中的缝合；(2) 捕获造山带对板块边界力不断变化的变形响应与从俯冲到碰撞的转变相关，从而量化板块强度和板块边界耦合在控制造山结构中的相对作用。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响进行评估，被认为值得支持审查标准。

项目成果

Diverse Deformation Mechanisms and Lithologic Controls in an Active Orogenic Wedge: Structural Geology and Thermochronometry of the Eastern Greater Caucasus

活动造山楔中的多种变形机制和岩性控制：大高加索东部的构造地质学和热测时法

• DOI: 10.1029/2022tc007349
• 发表时间: 2022-12
• 期刊: Tectonics
• 影响因子: 4.2
• 作者: Tye, A. R.;Niemi, N. A.;Cowgill, E.;Kadirov, F. A.;Babayev, G. R.
• 通讯作者: Babayev, G. R.

Tectonostratigraphy and major structures of the Georgian Greater Caucasus: Implications for structural architecture, along-strike continuity, and orogen evolution

格鲁吉亚大高加索地区的构造地层学和主要结构：对结构体系、沿走向连续性和造山带演化的影响

• DOI: 10.1130/ges02385.1
• 发表时间: 2022-01
• 期刊: Geosphere
• 影响因子: 2.5
• 作者: Trexler, Charles C.;Cowgill, Eric;Niemi, Nathan A.;Vasey, Dylan A.;Godoladze, Tea
• 通讯作者: Godoladze, Tea