Collaborative Research: Lithospheric removal: The Sierra Nevada as the prototype of a fundamental process in mountain building

合作研究：岩石圈去除：内华达山脉作为造山基本过程的原型

• 批准号: 0607831
• 负责人: Craig Jones
• 金额: $ 53.01万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-15 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0607831&HistoricalAwards=false
• 关键词: Collaborative; Research; Lithospheric; removal; Sierra

0607831JonesThe delamination of mantle lithosphere from continental crust is a fundamental tectonic process that is difficult to study. The goal of this project is to examine the removal of mantle lithosphere from under the Sierra Nevada. The PIs assert that the Sierras are an excellent place to look because delamination appears to have happened rather recently, and may still be happening. Preliminary studies indicate possible mantle "drips" at both ends of the Sierra. The proposal(s) seeks to identify the removal process and the fate of the delaminated portion..., i.e. the drips. Through combined magnetotelluric (MT), geochemistry, geomorphic studies and geodynamic modeling, integrated with existing and proposed passive seismic data, the PIs seek to gain understanding of how mantle lithosphere is removed, and the conditions that facilitate such removal. The hope is that this understanding can be applied elsewhere. Removal of mantle lithosphere may have played a key role in regions with histories and structures as diverse as the southern Sierra Nevada, the Alboran Sea, the Tibetan Plateau, the Apennines, the Appalachians, central Andes, the Carpathians, Precambrian South Africa, the North China Craton, and the Basin and Range. However, in many of these other regions where mantle lithosphere may have been removed, the removal is either too old or in an environment too complex, or logistically too difficult to expect a record as clear as in the Sierra. The proposed project will build on the results of two previously funded CD projects, the Southern Sierra Continental Dynamics Project (that found that the southern part of the range was supported not by thick crust, but by a hot, low-density upper mantle) and the Sierran Paradox Experiment (that discovered that eclogite had been removed from the base of the crust in the latest Miocene or Pliocene time).A strength of the project is the PI's intent to conduct a joint analysis of MT and seismic data. As stated, this joint analysis will use a more quantitative coupling of MT and seismic results based on the underlying physical properties which produce the observables (e.g. petrophysical behavior of mantle olivine and pyroxene based rocks with and without water). The PIs seek to tie seismic velocities and electrical resistivity via poisson's ratio, attenuation, and anisotropy. Such a joint inversion method, particularly if it can provide some measure of mantle hydration, would advance the ability to geophysically image the mantle lithosphere. This project is paired with a project that has been funded by EarthScope (Sierra Nevada EarthScope Project - SNEP) to conduct a seismological investigation with the FlexAray component of EarthScope in the central Sierra Nevada. The PIs of SNEP are G. Zandt, T. Owens, and C. Jones. Currently focused on the northern edge of the region where lithosphere is known to have been removed, the seismological work will place limits on the extent of lithosphere removal and delineate the seismological structures resulting from that removal. This CD project explores the variations in geological and other geophysical observations across the same region with the goal of identifying those features clearly associated with removal of the lithosphere. Although each of these studies will yield useful results without the other, the combination of them should exceed the sum of the separate parts.

地幔岩石圈与陆壳的拆沉作用是一个基本的构造过程，也是一个难以研究的问题。 这个项目的目标是研究从内华达州下地幔岩石圈的移动。 PI断言，塞拉山脉是一个绝佳的观察地点，因为分层似乎是最近发生的，而且可能仍在发生。 初步研究表明，在塞拉利昂的两端可能有地幔“滴”。 该提案旨在确定拆除过程和分层部分的命运.， 即滴液。 通过结合大地电磁（MT），地球化学，地貌研究和地球动力学建模，与现有的和拟议的被动地震数据相结合，PI寻求了解地幔岩石圈是如何被移除的，以及促进这种移除的条件。 希望这种理解可以适用于其他地方。 地幔岩石圈的移动可能在历史和结构多样的地区发挥了关键作用，这些地区包括南部的内华达州、阿尔沃兰海、青藏高原、亚平宁山脉、阿巴拉契亚山脉、中部的安第斯山脉、喀尔巴阡山脉、前寒武纪的南非、中国北部的东昆仑山脉以及盆地和山脉。 然而，在许多其他地区，地幔岩石圈可能已经被移除，移除要么太老，要么环境太复杂，要么逻辑上太难期望像Sierra一样清晰的记录。 拟议的项目将建立在两个先前资助的CD项目的成果基础上，（发现山脉的南部不是由厚地壳支撑的，而是由热的，低密度上地幔）和Sierran Partial实验（发现榴辉岩在中新世或上新世晚期从地壳底部被移走）该项目的一个优势是PI打算对MT和地震数据进行联合分析。 如前所述，该联合分析将根据产生可观测值的基本物理性质（例如，地幔橄榄石和辉石基岩石在有水和无水情况下的岩石物理行为），对MT和地震结果进行更定量的耦合。 PI试图通过泊松比、衰减和各向异性来联系地震速度和电阻率。 这种联合反演方法，特别是如果它可以提供一些地幔水化的措施，将提高能力，地幔岩石圈的成像。 该项目与EarthScope资助的一个项目（Sierra内华达州EarthScope项目- SNEP）相结合，利用EarthScope的FlexAray组件在Sierra内华达州中部进行地震调查。 SNEP的PI为G. Zandt，T. Owens和C.琼斯 地震学工作目前集中在已知岩石圈已被移走的区域的北方边缘，将对岩石圈移走的范围加以限制，并描绘出移走所造成的地震学结构。 这个CD项目探索了同一地区地质和其他地球物理观测的变化，目的是确定那些与岩石圈移动明显相关的特征。 虽然这些研究中的每一项都将产生有用的结果，但它们的组合应该超过单独部分的总和。