Collaborative Research: Structure of the Nazca slab and Sierras Pampeanas

在俯冲带内，一个构造板块潜入另一个板块之下，并将物质循环回地幔。与俯冲带相关的压力产生了地球上一些最高的山脉和最大的地震。纳斯卡板块俯冲到南美洲西部的地幔中。在阿根廷中部，它以非常低的角度俯冲，在下沉到地幔之前在浅层深处停留100公里；这是当今世界上浅层俯冲最极端的例子。位于阿根廷中部帕米亚山脉东部的科尔多瓦山脉标志着纳斯卡板块最终下降到地幔中的位置。该山脉与板块倾斜度变化的搭配表明了一种联系，但应力如何从板块转移到上覆板块以抬升山脉的方法仍然难以捉摸。这个项目的重点是确定力可以从下降的纳斯卡板块通过地幔楔向上转移到南美岩石圈的机制。Cordoba地区有大量的地壳形变和地震活动；这项研究将通过提高对岩石圈动力学的理解，帮助描述Cordoba附近的地震危险。来自阿根廷的研究人员和学生的参与，以及我们在数据分析、解释和新思想和理论发展方面的合作，使该项目的国际组成部分成为其主要优势之一。这项研究的资助反映了其国际组成部分的突出地位，因为地球科学部的地球物理计划得到了国际科学与工程办公室的资助。对于与平板俯冲有关的上覆板块和俯冲板块的力学、动力学和结构，存在着许多争论。该项目正在部署数字地震仪系统，以调查阿根廷中部东部sierra Pampeanas山脉的深层结构，以确定其起源的细节。位于帕玛尼亚山脉东部的活跃基底隆起，覆盖在浅俯冲的纳斯卡板块之上，为研究平板对地表变形的影响提供了理想的区域。这项实验的科学目标包括确定覆盖南美岩石圈从其边缘变形的机制和模式，以及理解为什么下行纳斯卡板块的俯冲角在以浅角度穿越100公里后变得陡峭。此外，还将研究板块内的水和其他挥发物在下降到地幔中时的命运，以确定脱挥发物是如何导致上板块内的变形或影响浅俯冲板块与上覆板块之间的耦合的。这些知识将适用于了解美国西部地区（如犹他州、科罗拉多州和怀俄明州）过去（侏罗纪到创造纪）的变形。

Within subduction zones, one tectonic plate dives beneath another and recycles material back into the mantle. Stresses associated with subduction zones produce some of the highest mountains and largest earthquakes around the Earth. The Nazca plate subducts into the mantle beneath the western portion of South America. In central Argentina, it subducts at a very low angle and remains at shallow depths for 100's of kilometers before sinking into the mantle; this is the most extreme example of present day shallow subduction in the world. The Sierras de Cordoba in the eastern Sierras Pampeanas of central Argentina mark the location where the Nazca slab eventually descends into the mantle. The collocation of this mountain range with the change in slab dip suggests a connection, but the means by which stresses may be transferred from the slab to the overriding plate to uplift the mountains remain elusive. This project is focused on identifying the mechanisms through which forces could be transferred from the descending Nazca plate up though the mantle wedge and into the South American lithosphere. A great deal of active crustal deformation and seismcity occurs in the Sierras de Cordoba region; this study will help characterize the seismic hazards in the vicinity of Cordoba through improved understanding of lithospheric dynamics that will come from this study. The involvement of researchers and students from Argentina, and our resulting collaboration on data analysis, interpretation, and development of new ideas and theories, make the international component of this project one of its major strengths. The funding of this research reflects the prominence of its international component as the Geophysics program, within the Division of Earth Science, supports this project with a contribution from the Office of International Science and Engineering.There is much debate about the mechanics, dynamics, and structure of both the overriding plate and subducting slab related to flat-slab subduction. This project is undertaking a deployment of digital seismograph systems to investigate the deep structure of the eastern Sierras Pampeanas mountain range in central Argentina in order to determine details of their origin. Active basement uplifts within the eastern Sierras Pampeanas, which overlie the shallowly subducting Nazca plate, offer an ideal region to investigate the influence of flat slabs on surface deformation. The scientific goals of this experiment include determining the mechanism and mode by which the overriding South American lithosphere deforms away from its margin and understanding why the subduction angle of the downgoing Nazca plate steepens after traversing 100's of km at a shallow angle. Additionally, the fate of water, and other volatiles, within the slab as it descends into the mantle will be investigated to determine how devolatization may contribute to deformation within the upper plate or influence the coupling between shallowly subducting slabs and the overriding plate. Such knowledge will be applicable to understanding past (Jurrassic to Createcous) deformation in regions of the western United States such as Utah, Colorado, and Wyoming.