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.

板片断裂是指板片从俯冲板块中脱离并沉入地幔的过程，它从根本上改变了会聚边缘的作用力，因而对碰撞造山带的地球动力学演化具有一级控制作用。模拟表明，可观察到的特征断裂内的碰撞造山带包括俯冲的洋盆碰撞前，一个短暂的脉冲加速岩石和表面隆起带，收敛率下降的断裂和增加以上的相邻部分的板片保持连接。然而，在大陆碰撞区内对这一过程的地质观测并没有很好的记录。这个加州戴维斯大学和密歇根大学的研究团队，与他们的国际合作伙伴合作，探索了大高加索（黑海和里海之间）最近的地质历史是这一过程的结果的想法。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，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，发展具有全球竞争力的STEM劳动力;（二）增加学术界与碳氢化合物工业之间的伙伴关系，加强现有合作，并与亚美尼亚、格鲁吉亚、台湾和加拿大的科学家。该项目将为研究生提供丰富的国际研究经验。该项目得到了构造学计划和美国国家科学基金会国际科学与工程计划的支持，该研究项目将检验大高加索山脉反映了该山脉西部板块断裂的瞬时地球动力学响应的假设。这一事件发生在渐新世至上新世一个残留洋盆关闭之后，该洋盆的俯冲目前仍在山脉东半部之下继续。该研究小组将利用结构测绘和平衡剖面对这一研究很少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，进行基岩低温热年代测定和新构造调查。他们的目标是限制新生代缩短横跨大高加索沿着三个造山带垂直部分的幅度，并从低温热年代学中得出大高加索和小高加索的折返历史。整合这些数据与碎屑物源和滞后时间分析相邻的沉积盆地将捕获地质响应的一个短暂的地球动力学事件，并记录也许是第一个证据板剥离在俯冲碰撞过渡的活动造山带。