Collaborative Research: Understanding Lithospheric Suturing and Passive Margin Development Beneath the Southeastern U.S.

合作研究：了解美国东南部岩石圈缝合和被动边缘发育

• 批准号: 0844276
• 负责人: Karen Fischer
• 金额: $ 47.6万
• 依托单位: Brown University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0844276&HistoricalAwards=false
• 关键词: Collaborative; Research; Understanding; Lithospheric; Suturing

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).At the culmination of the lithospheric accretion that built the Appalachian Mountains (250-320 million years ago) the lithosphere of another continent (Gondwana) collided with proto-North America. The suture between these two lithospheres is delineated in the crust beneath southern Georgia by variations in fossils, rock types and ages, and a zone of southward dipping reflectors imaged by seismic reflection data. However, the location and geometry of the suture in the mantle is unknown.The goal of this project is to determine the position and shape of the lithospheric suture in the mantle, and to measure any contrasts in crust and mantle physical and chemical properties across the suture. 85 EarthScope USArray Flexible Array broadband stations are being deployed in two N-S linear arrays that straddle the suture. One line stretches from North Carolina to the coast of the Florida panhandle. The other extends from South Carolina into central Florida. These stations, together with the stations of the EarthScope USArray Transportable Array, will record seismic waves from around the globe. These data will be analyzed to measure three-dimensional variations in isotropic and anisotropic wave velocities, and the velocity models will be interpreted in terms of temperature, rock composition (including volatile content), and rock deformation fabrics.This research will address a series of fundamental questions. How does the crustal suture connect to mantle structures? Did mantle accretion occur on shallow dipping shear zones, or did it occur at least in part on more vertical contacts that imply horizontal shortening over a broad depth range? If dipping mantle interfaces exist, do they represent relict subducted lithosphere, or are they shear zones unrelated to prior subduction? What does anisotropy in seismic velocities imply about the distribution of deformation during accretion? What was the direction of subduction associated with the collision of Gondwana and Laurentia? Continental break-up followed the lithospheric collision, leading to the opening of the Atlantic Ocean. How was the continental lithosphere affected by this episode of extension, rifting and magmatism? Is there evidence for delamination of the lithosphere? What are the present-day patterns of flow in the weak mantle asthenosphere that underlies the lithosphere?This project is directly supporting the education and training of graduate and undergraduate students. We are developing educational materials that use this research project to build understanding of concepts such as continental collision, mountain building, and continental break-up. Experiment results will be used in our undergraduate and graduate classes, and in outreach to schools in the vicinity of our home institutions in Georgia, North Carolina, and Rhode Island.

该奖项是根据2009年的《美国回收与再投资法》（公法111-5）资助的。在建造阿巴拉契亚山脉（250-3.2亿年前）的岩石圈积聚的高潮中，另一个大陆（Gondwana）（Gondwana）的岩石圈（Gondwana）与Pato-North America相撞。这两个岩石圈之间的缝合线在佐治亚州南部的地壳下通过化石，岩石类型和年龄的变化以及通过地震反射数据成像的南向反射镜的变化来描述。 然而，地幔中缝合线的位置和几何形状尚不清楚。该项目的目的是确定岩石圈缝合线在地幔中的位置和形状，并测量缝合线跨缝合线的物理和化学特性中的任何对比度。 85 EarthScope USARRAY柔性阵列宽带站被两个N-S线性阵列部署，这些阵列跨越了缝合线。一条线从北卡罗来纳州一直延伸到佛罗里达潘汉德尔的海岸。另一个从南卡罗来纳州延伸到佛罗里达州中部。这些电台以及Earthscope USArray可运输阵列的电台将记录来自全球各地的地震波。将分析这些数据以测量各向同性和各向异性波速度的三维变化，并且速度模型将以温度，岩石组成（包括挥发性含量）和岩石变形织物来解释。这项研究将解决一系列基本问题。地壳缝合线如何连接到地幔结构？地幔积聚是否发生在浅浸入剪切区上，还是至少部分发生在更垂直的接触中，这意味着在宽深度范围内水平缩短？如果存在倾斜地幔界面，它们是否代表了遗物的悬崖岩石圈，还是剪切带与先前俯冲无关的剪切区？地震速度的各向异性暗示着增生过程中变形的分布？俯冲的方向与冈瓦纳（Gondwana）和劳伦（Laurentia）的碰撞有关？岩石圈碰撞发生后，大陆分裂导致大西洋开放。大陆岩石圈如何受到这一延伸，裂谷和岩浆作用的影响？是否有岩石圈分层的证据？岩石圈基础的弱陆层薄圈中的流动方式是什么？该项目直接支持研究生和本科生的教育和培训。我们正在开发使用该研究项目的教育材料来建立对诸如大陆碰撞，山区建筑和大陆分手等概念的理解。实验结果将用于我们的本科和研究生班，并与我们位于佐治亚州，北卡罗来纳州和罗德岛州的家庭机构附近的学校相邻。