Petrologic Constraints on Subduction Termination From Lamprophyres, Ross Orogen, Antarctica

俯冲发生在会聚板块边界，包括一个构造板块下沉到另一个构造板块之下。虽然这一过程是板块构造的一个关键方面，在地质时期塑造了地球，是地震的主要原因，但人们不知道是什么原因导致俯冲停止，以及它对地壳最深处和地幔上部有什么影响。 该项目通过研究俯冲循环最后阶段所侵位的火成岩的年龄和成分，试图了解是什么导致俯冲停止，以及这如何改变地壳和上地幔的成分和结构。由于这一过程发生在地球深处，该项目将重点关注古代俯冲带根部的岩石，现在暴露在南极洲的横贯南极山脉。此外，对南极洲的了解仍然相对较少，该项目将直接有助于提高我们对该地区地质历史的了解。该项目将侧重于培训研究生和本科生-将实践经验与一系列最先进的分析仪器相结合。学生还将获得一系列更通用的技能，包括地理信息系统（GIS），书面和口头沟通，以及数据管理-这些优势与学术和地球科学行业的职业高度相关。每年夏天，高中生将通过UCSB研究导师计划被纳入实验室研究的各个方面。PI和研究生将通过专门构建的iPhone应用程序和多媒体网站与公众互动。活动将包括小学生和南极队成员之间的现场电话和视频对话。深部地壳分层或“奠基者”返回地幔的机制仍然是地球科学中的一个基本问题。具体而言，人们对这一过程发生的时间和空间尺度或触发此类灾难性事件的机制知之甚少。富含钾的火成岩，称为层状岩，通常在俯冲终止期间和之后立即就位，因此可能提供对下沉的直接了解。这些神秘的岩石是重要的，因为它们代表了近原生地幔熔体成分，因此它们的年龄，地球化学和岩石学演化揭示了上地幔的组成和热状态的关键信息。同样重要的是，它们揭示了这些关键参数在空间和时间上的变化。通过评价沿着俯冲带边缘的层状构造，可以提取：1）局部尺度的信息，如熔融的时间和持续时间以及火成岩结晶过程在同位素不均匀性产生中的作用; 2）地幔源成分、温度和熔融深度的沿走向变化; 3）控制下沉和俯冲终止的板块尺度力。该项目将研究南极洲新元古代-奥陶纪罗斯造山带最后阶段（距今约5.05亿至4.7亿年）期间形成的沿横贯南极山脉轴线沿着的一套层状岩石。高精度地质年代学（年龄测定）将与岩石和矿物的地球化学测量相结合，以了解地壳深部沉降/分层的机制和时间。

Subduction takes place at convergent plate boundaries and involves sinking of one tectonic plate underneath another. Although this process is a key aspect of plate tectonics that shapes the planet over geologic time, and is a primary cause of earthquakes, it is not known what causes subduction to cease, and what effect it has on the deepest portions of the crust and the upper part of the mantle. By studying the age and composition of igneous rocks emplaced at the very end of the subduction cycle, this project seeks to understand what causes subduction to cease, and how this changes the composition and structure of the crust and upper mantle. Because this process occurs deep within the earth, the project will focus on rocks in the root of an ancient subduction zone, now exposed in the Transantarctic Mountains of Antarctica. In addition, Antarctica remains relatively poorly understood, and this project will contribute directly to increasing our understanding of the geologic history of this region. The project will focus on training graduate and undergraduate students - incorporating hands-on experience with an array of state-of-the-art analytical instrumentation. Students will also gain a range of more general skills including Geographic Information Systems (GIS), written and oral communication, and data management - strengths that are highly relevant to careers both in the academic and Geosciences industry. Each summer, high school students will be incorporated into aspects of the laboratory-based research through the UCSB research mentorship program. The PI and graduate students will engage the general public through a purpose-built iPhone App and multimedia website. Activities will include live phone and video conversations from the field between elementary school students and members of the team in Antarctica. The mechanisms by which the deep crustal delaminates or "founders" and is returned to the mantle remains a fundamental problem in earth science. Specifically, little is known about the temporal and spatial scales over which this process occurs or the mechanisms that trigger such catastrophic events. Igneous rocks highly enriched in potassium, called lamprophyres, are often emplaced during, and immediately after, termination of subduction and therefore potentially provide direct insight into foundering. These enigmatic rocks are important because they represent near-primary mantle melt compositions and therefore their age, geochemistry and petrologic evolution reveal key information on both the composition of the upper mantle and its thermal state. Of equal importance, they reveal how these key parameters vary through both space and time. By evaluating lamprophyres along a subduction zone margin it is possible to extract: 1) local-scale information, such as the timing and duration of melting and the role of igneous crystallization processes in generation of isotopic heterogeneities; 2) along-strike variations in mantle source composition, temperature, and depth of melting 3) the plate-scale forces that control foundering and termination of subduction. This project will study a suite of lamprophyres along the axis of the Transantarctic Mountains, emplaced during the latest stages of the Neoproterozoic - Ordovician Ross orogeny, Antarctica (roughly 505 to 470 million years before present). High-precision geochronology (age determinations) will be combined with geochemical measurements on the rocks and minerals to understand the mechanisms and timing of deep crustal foundering/delamination.