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: 0607702
• 负责人: Linda Elkins-Tanton
• 金额: $ 8.86万
• 依托单位: Brown University
• 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 2007-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0607702&HistoricalAwards=false
• 关键词: Collaborative; Research; Lithospheric; removal; Sierra

0607702Elkins-TantonThe 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.

0607702Elkins-Tanton，大陆壳的地幔岩石圈的分层是难以研究的基本构造过程。 该项目的目的是检查内华达山脉下的地幔岩石圈的去除。 PIS断言，山脉是一个很好的外观场所，因为分层似乎最近发生了，并且可能仍在发生。 初步研究表明塞拉两端可能的地幔“滴”。 该提议旨在确定拆除过程和分层部分的命运...，即滴水。 通过磁铁联合（MT），地球化学，地球化学研究和地球动力学建模，与现有和拟议的被动地震数据整合在一起，PIS试图了解如何去除地幔岩石圈以及促进此类去除的条件。 希望这种理解可以在其他地方应用。 地幔岩石圈的去除可能在具有与南部内华达州南部山脉，阿尔博兰海，藏族高原，阿皮纳尼斯，阿巴拉契亚山脉，阿巴拉契亚人，安德斯中部，喀尔巴阡山脉，喀尔巴阡山脉，南非，北非南非，北部南非，北非，北非，北部，北非，北非，南非，北部，北非，北部，南非，北部，南非，北部，南非，北部，北部，南非，南部，北部，北部，北部高原，北部，阿尔博兰海，南部，北部，北部，北部，北部，北部，北部，北部，北部，北部，北部，北部，中国克拉顿以及盆地和山脉。 但是，在许多其他可能已经去除地幔岩石圈的区域中，去除太老了，要么在环境中太复杂，或者在逻辑上太难期望记录像塞拉山脉一样清晰。 拟议的项目将建立在两个先前资助的CD项目的结果基础上Sierran悖论实验（发现在最新的中新世或上新世时期从地壳的底部清除了Eclogite）。该项目的强度是PI的意图对MT和地震数据进行联合分析。 如前所述，该联合分析将基于产生可观察物的潜在物理特性（例如，地幔橄榄石和带有水和不含水的吡喃烷基的岩石的岩石物理行为）对MT和地震结果进行更定量的耦合）。 PI寻求通过泊松比，衰减和各向异性将地震速度和电阻率绑定。 这种关节反转方法，特别是如果它可以提供一定的地幔水合度量，将提高地球物理对地幔岩石圈的地球物质成像的能力。 该项目与一个由Earthscope（内华达州塞拉达地球项目-SNEP）资助的项目配对，以与内华达州中部塞拉利昂的Earthscope的Flexaray组成部分进行地震学研究。 Snep的PI是G. Zandt，T。Owens和C. Jones。 目前，人们专注于已知已知岩石圈的北部边缘，地震学工作将对去除岩石圈的范围施加限制，并描述由于该去除而导致的地震结构。 该CD项目探讨了同一区域的地质和其他地球物理观测的变化，目的是识别与岩石圈去除的那些特征。 尽管这些研究中的每一个都将产生有用的结果，但它们的组合应超过单独部分的总和。