Collaborative Research: Structure of the Nazca slab and Sierras Pampeanas

在俯冲带内，一个构造板块俯冲到另一个板块之下，并将物质回收到地幔中。与俯冲带有关的压力会产生一些地球上最高的山脉和最大的地震。纳斯卡板块俯冲到南美洲西部下方的地幔中。在阿根廷中部，它以很低的角度俯冲，并在浅层保持100‘S公里的深度，然后沉入地幔；这是当今世界上最极端的浅层俯冲例子。位于阿根廷中部Sierras Pampeas东部的Sierras de Cordoba标志着纳斯卡板块最终落入地幔的位置。这条山脉与板块倾角的变化表明了一种联系，但将应力从板块转移到逆冲板块以抬升山脉的方法仍然难以捉摸。该项目的重点是确定力量可以通过哪些机制从纳斯卡板块下沉向上穿过地幔楔子进入南美洲岩石圈。Sierras de Cordoba地区发生了大量活跃的地壳形变和地震活动；这项研究将有助于通过这项研究对岩石圈动力学的更好理解，来描述科尔多瓦附近的地震灾害。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、解释和开发新想法和理论方面的合作，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，因为地球科学部内的地球物理计划由国际科学与工程办公室提供支持。关于与平板俯冲有关的俯冲板块和俯冲板块的力学、动力学和结构存在很大争议。该项目正在部署数字地震仪系统，以调查阿根廷中部东部Sierras Pampeas山脉的深部结构，以确定其起源的细节。在浅俯冲的纳斯卡板块之上的东部Sierras Pampeas内部的活跃的基底隆起为研究平板对地表变形的影响提供了一个理想的区域。这项实验的科学目标包括：确定俯冲的南美岩石圈偏离其边缘的机制和方式，以及理解向下的纳斯卡板块在以浅角穿越100‘S公里后俯冲角度变陡的原因。此外，将调查水和其他挥发物在板块内下降到地幔中的命运，以确定去挥发作用如何可能导致上板块内的变形，或影响浅俯冲板块和俯冲板块之间的耦合。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)的过去(侏罗纪至Createcous)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.