Collaborative Research: A Structural, Thermochronologic, and Provenance Investigation of a Hypothesized Transition From Subduction to Slab Breakoff in the Greater Caucasus

合作研究：对大高加索地区从俯冲到板块断裂的假设转变的结构、热年代学和起源调查

• 批准号: 1524631
• 负责人: Eric Cowgill
• 金额: $ 27.54万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1524631&HistoricalAwards=false
• 关键词: Collaborative; Research; Structural; Thermochronologic; Provenance

Slab breakoff, in which a slab detaches from a subducting plate and sinks into the mantle, exerts a first-order control on the geodynamic evolution of collisional orogenic belts because breakoff fundamentally alters the forces along the convergent margin. Modeling indicates that observable characteristics of breakoff within a collisional orogen include subduction of an ocean basin before collision, a transient pulse of accelerated rock and surface uplift in the belt, a decrease in convergence rate over the breakoff and an increase above adjacent parts of the slab that remain attached. However, geologic observations of this process within continental collision zones are not well documented. This University of California Davis and University of Michigan research team, in collaboration with their international partners, in explores the idea that the recent geological history of the Greater Caucasus (between the Black Sea and the Caspian Sea) is a consequence of this process. The project will advance desired societal outcomes by: (1) development of a globally competitive STEM workforce through the training of several U.S. graduate students, involvement of undergraduate students in research, and training of graduate students from Georgia, Armenia, and Azerbaijan; (2) increased partnerships between academia and the hydrocarbon industry and strengthening of existing collaborations and the development of new collaborations with scientists in Armenia and Georgia, Taiwan, and Canada. The project would provide the graduate students with rich international research experiences. The project is supported by the Tectonics Program and NSF's International Science and Engineering program.This research project will test the hypothesis that the Greater Caucasus reflects the transient geodynamic response to recent slab breakoff beneath the western portion of the range. This event follows the Oligocene to Pliocene closure of a remnant ocean basin, subduction of which presently continues beneath the eastern half of the range. The research team will carry out a field investigation of this little-studied orogen using structural mapping and balanced cross-sections, sediment provenance studies using U-Pb analyses of detrital zircons and (U-Th)/He analyses of apatite, bedrock low-temperature thermochronometry, and neotectonic investigations. They aim to constrain the magnitude of Cenozoic shortening across the Greater Caucasus along three orogen-perpendicular sections, and to derive the exhumation history of the Greater and Lesser Caucasus from low-temperature thermochronometry. Integration of these data with detrital provenance and lag time analyses of adjacent sedimentary basins will capture the geologic response to a transient geodynamic event and record perhaps the first evidence for slab detachment at the subduction-to-collision transition in an active orogen.

板块断裂，即板块从俯冲板块上分离并沉入地幔的过程，对碰撞造山带的地球动力学演化起着一级控制作用，因为板块断裂从根本上改变了沿辐合边缘的力。模拟表明，碰撞造山带内断裂的可观测特征包括碰撞前海洋盆地的俯冲，带内加速岩石和地表隆起的瞬态脉冲，断裂上的收敛速率降低，而相邻板块上仍然附着的收敛速率增加。然而，在大陆碰撞带内对这一过程的地质观察并没有很好的记录。加州大学戴维斯分校和密歇根大学的研究小组与他们的国际合作伙伴合作，探讨了大高加索地区（黑海和里海之间）最近的地质历史是这一过程的结果。该项目将通过以下方式促进预期的社会成果：(1)通过培训几名美国研究生，让本科生参与研究，以及培训来自格鲁吉亚、亚美尼亚和阿塞拜疆的研究生，发展一支具有全球竞争力的STEM劳动力队伍；(2)加强学术界与油气行业之间的伙伴关系，加强与亚美尼亚、格鲁吉亚、台湾和加拿大科学家之间的现有合作和发展新的合作。该项目将为研究生提供丰富的国际研究经验。该项目由构造学计划和NSF国际科学与工程计划支持。该研究项目将验证大高加索地区反映了该山脉西部板块近期断裂的瞬态地球动力学响应的假设。这一事件发生在渐新世至上新世的一个残余海洋盆地关闭之后，该盆地的俯冲作用目前在山脉的东半部下方继续进行。研究小组将利用构造作图和平衡横截面对这一鲜有研究的造山带进行实地调查，利用碎屑锆石的U-Pb分析和磷灰石的(U-Th)/He分析进行沉积物来源研究，基岩低温热时测定和新构造调查。他们的目标是沿着三个垂直于造山带的剖面限制大高加索地区新生代缩短的幅度，并通过低温热时测定法推导出大高加索地区和小高加索地区的发掘历史。将这些数据与相邻沉积盆地的碎屑物源和滞后时间分析相结合，将捕捉到对短暂地球动力学事件的地质响应，并可能记录下在活动造山带俯冲到碰撞转变过程中板块分离的第一个证据。