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.

平板断裂，其中平板从俯冲板中脱离并沉入地幔中，对碰撞造山带的地球动力学演化施加了一阶控制，因为断裂从根本上改变了沿收敛缘的力。建模表明，碰撞造成的可观察到的破裂特征包括碰撞前的海盆俯冲，皮带中加速岩石和表面上升的瞬态脉冲，在断裂中的收敛速度降低以及在保持附着的平板的邻近部分上方增加。但是，在大陆碰撞区域内对这一过程的地质观察没有充分记录。加州大学戴维斯分校和密歇根大学研究团队与国际合作伙伴合作，探讨了以下观点：大高加索地区最近的地质历史（黑海和里海之间）是这一过程的结果。该项目将通过：（1）通过培训几位美国研究生的培训，本科生参与研究的研究以及对佐治亚州，亚美尼亚和阿塞拜疆的研究生的培训来提高所需的社会成果； （2）学术界与碳氢化合物行业之间的合作伙伴关系增加，并加强现有合作以及与亚美尼亚和乔治亚州，台湾和加拿大科学家的新合作发展。该项目将为研究生提供丰富的国际研究经验。该项目得到了构造计划和NSF的国际科学与工程计划的支持。该研究项目将检验以下假设：更大的高加索反映了该范围西部以下的近期平板断裂的短暂地球动力学反应。这一事件是在残留海洋盆地的渐新世至上新世封闭之后，目前俯冲在该范围的东半部。研究小组将使用结构映射和平衡的横截面，使用U-PB分析碎屑锆石的分析以及（U-TH）/HE分析磷灰石，基岩低温层状热量学和NeoTecticonics研究。它们的目的是限制沿三个基质 - 垂直截面的大高加索地区的新生代缩短的大小，并从低温热化学学中得出大量和较少的高加索的发掘历史。将这些数据与相邻沉积盆地的碎屑出处和滞后时间分析的整合将捕获对瞬态地球动力学事件的地质响应，并记录了在活性造口中俯冲到倾斜过渡时平板脱离的第一个证据。