Collaborative Research: Constraining the thermal conditions of the subduction interface by integrating petrology and geodynamics

合作研究：通过整合岩石学和地球动力学来约束俯冲界面的热条件

基本信息

批准号：
1850634
负责人：
Peter van Keken
金额：
$ 3.66万
依托单位：
Carnegie Institution of Washington
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-04-01 至 2024-03-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1850634&HistoricalAwards=false
关键词：
Collaborative Research Constraining thermal conditions

项目摘要

Subduction zones are places on Earth where one of Earth's tectonic plates dives beneath another. They are the location of many societally-relevant hazards, including the generation of Earth's deadliest earthquakes, such as the 2011 Tohoku earthquake and associated tsunami, and volcanic eruptions such as those at Mt St Helens (1980) and Mt Pinatubo (1991). The processes that lead to these earthquakes and volcanoes are ultimately dependent on the thermal structure of subduction zones - that is how hot it is at great depths. Metamorphic rocks exhumed from ancient subduction zones contain unique records of the temperatures that they witnessed as they traveled down a subduction zone before being exhumed. Geodynamic models and geophysical observations provide estimates of the thermal structures of present-day subduction zones. Interestingly, the rock record suggests significantly warmer conditions than those predicted for modern subduction zones. The proposed work will investigate the reasons for this discrepancy, which may lie in the way we interpret conditions from the rocks, the way they are exhumed, or even in how we compare model predictions and the rock record.This proposal aims to address the rock-model discrepancy through two key questions: 1) Does our current interpretation of the rock record accurately represent the thermal structure of the associated ancient subduction zone? and 2) Did rocks get exhumed from ancient subduction zones that were hotter on average than modern subduction zones? To address Question 1 this team will determine P-T conditions for metamorphic rocks exhumed from five well-characterized localities that represent a range of thermal structures using relatively new analytical methods: trace element thermometers (e.g. Zr-in-rutile) and mineral inclusion barometers (e.g. quartz-in-garnet barometry). To address Question 2, they will develop geodynamical models of the ancient subduction zones represented by the exhumed rocks. These models will incorporate the effects of region-specific subduction dynamics, such as variations in slab age and subduction rate with time, subduction initiation, ridge subduction, and slab breakoff, when applicable. The model-predicted P-T conditions along the subduction interface will be compared with the newly produced P-T estimates to re-evaluate their disparity. The two-pronged approach of combining petrological observations and geodynamical modeling allows quantitative exploration of the thermal evolution of subduction zones. Subduction-related metamorphic rocks are the only direct samples of material from the plate interface; evaluating the P-T conditions using the latest thermobarometric approaches will provide the team with a more accurate and precise way to untangle the complex history they have experienced. Through geodynamical modeling, the effects of individual parameters on the thermal structure of subduction zones can be isolated, and this targeted approach will allow evaluation of possible explanations for the warm conditions that are recorded by exhumed rocks. The application of the two-pronged approach to the selected ancient subduction localities will allow researchers to determine whether the disparity can be reconciled. The results of this work have important implications for many processes, including geochemical cycling of volatiles, construction of continental crust, and the conditions that lead to arc volcanism. This work will engage graduate students and early career scientists in new collaborations between scientists of different disciplines (petrologists and geodynamicists) and at different institutions both in the US and abroad. EarthCache (TM) sites will be created in California (Franciscan and Catalina) as part of the project. These sites will engage the public in geoscience through the popular activity of geocaching and will disseminate information about subduction zone geology through information tied to direct observations of geologic features exhumed from subduction zones.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.

俯冲带是地球上一个地球构造板在另一个地下潜水的地方。它们是许多与社会相关的危害的所在地，包括地球上最致命的地震，例如2011年Tohoku地震和相关的海啸，以及火山喷发，例如ST Helens MT（1980）和Pinatubo Mt Pinatubo（1991）。导致这些地震和火山的过程最终取决于俯冲带的热结构 - 这在很大程度上是多么热。从古老的俯冲带中挖掘出的变质岩石包含他们在俯冲带前往俯冲带之前所目睹的独特记录，然后被挖掘出来。地球动力学模型和地球物理观测提供了当今俯冲带的热结构的估计。有趣的是，岩石记录比现代俯冲带预测的条件明显温暖。 The proposed work will investigate the reasons for this discrepancy, which may lie in the way we interpret conditions from the rocks, the way they are exhumed, or even in how we compare model predictions and the rock record.This proposal aims to address the rock-model discrepancy through two key questions: 1) Does our current interpretation of the rock record accurately represent the thermal structure of the associated ancient subduction zone? 2）从平均比现代俯冲带更热的古老俯冲带中挖出了岩石？为了解决问题1，该团队将确定使用相对新的分析方法代表一系列热结构的变质岩石的P-T条件：痕量元素温度计（例如ZR-In-In-Rutile）和矿物包含气压仪（例如Quartz-in-Garnet Barometry）。为了解决问题2，他们将开发以被挖掘的岩石代表的古代俯冲区的地球动力学模型。这些模型将结合特定区域的俯冲动力学的影响，例如随时间的变化和俯冲率随时间的变化，俯冲启动，脊俯冲和板折断（如果适用）。将沿俯冲界面的模型预测的P-T条件与新产生的P-T估计值进行比较，以重新评估其差异。结合岩石学观测和地球动力学建模的两种普通方法允许对俯冲带的热演化进行定量探索。俯冲相关的变质岩是板界面中唯一的材料的直接样品。使用最新的热压方法评估P-T条件将为团队提供更准确，更精确的方法，以解开他们所经历的复杂历史。通过地球动力学建模，可以隔离单个参数对俯冲带热结构的影响，这种目标方法将允许评估对被发掘岩石记录的温暖条件的可能解释。两种义方法在选定的古代俯冲区域的应用将使研究人员能够确定是否可以调和差异。这项工作的结果对许多过程具有重要意义，包括挥发物的地球化学循环，大陆壳的建造以及导致弧火山的条件。这项工作将吸引研究生和早期的职业科学家，参与不同学科（岩石学家和地球动力学家）的科学家之间的新合作，并在美国和国外的不同机构中。该项目的一部分将在加利福尼亚（方济各会和卡塔琳娜州）创建Earthcache（TM）站点。这些站点将通过大众地球缓存活动吸引公众参与地球科学，并通过与直接观察俯冲区的地质特征有关的信息传播有关俯冲区地质的信息。该奖项反映了NSF的法定任务，并通过使用该基金会的知识优点和广泛影响来评估NSF的法定任务，并被认为是值得的。