Collaborative Research: Testing For Channel Flow and Ductile Extrusion In The Southeastern New England Appalachians Using An integrated Geophysical and Geological Approach

合作研究：使用综合地球物理和地质方法测试新英格兰东南部阿巴拉契亚山脉的河道流动和延性挤压

• 批准号: 2220233
• 负责人: Yvette Kuiper
• 金额: $ 29.44万
• 依托单位: Colorado School of Mines
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-07-15 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2220233&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; Channel; Flow

The formation of mountain belts is one of the most important processes that takes place on Earth. Mountain belts affect the distribution of key Earth resources, including economically important minerals, petroleum, and water. They form as a result of plate tectonics, along boundaries between converging plates. When mountain ranges become too high to be stable, the mountain belt may expand laterally, or material may ‘escape’ from the belt, due to the force of gravity. This escape may occur along faults that are exposed at the surface, where material is pushed away sideways from the mountain belt, or simply by collapse of material from higher to lower elevation. At mid-to deep-crustal levels (more than ten kilometers below the Earth’s surface) rocks flow in a fluid-like manner. In present-day mountain belts such as the Himalaya, these fluid-like rocks can be squirted away from the mountain belt, either toward the surface or entirely below the surface along tabular channels. These are important processes that contribute to the formation and modification of mountain belts, but they remain imperfectly understood. Specifically, because these rock flow zones are often below the surface, they are difficult to investigate in present-day mountain belt systems. The purpose of this project is to investigate an ancient flow zone in eastern Massachusetts that formed about 420 to 360 million years ago and today is partially exposed at the surface. Geological techniques will be used to investigate the zone at the surface and geophysical imaging techniques to elucidate the subsurface geometry. A better understanding of the formation of these flow zones will help us understand both ancient and modern mountain building processes in more detail, with important implications for our understanding of how Earth resources are distributed. This project will involve multi-disciplinary research that brings together geologists and geophysicists working in the Appalachians, and is synergistic with ongoing national and international collaborations. This project will contribute to the training of undergraduate and graduate students, with a focus on training students from historically untapped groups through various programs at the Colorado School of Mines and Yale University.An integrated geophysical and geological approach will be used to test a model of channel flow and ductile extrusion for one of the Appalachian terranes, the Nashoba terrane, in SE New England. Channel flow is flow of a weak, partially molten mid- to lower crustal layer between more competent overlying and underlying crust as a result of crustal thickening and pressure gradients. Localized denudation at the surface may cause ductile extrusion towards the surface. The purpose of this project is not only to further test a hypothesis for the evolution of the Nashoba terrane based on field and geochronology data, but also to visualize ductile flow of rocks during the geologic past below the surface using geophysical data. To do this, a tightly spaced array of six broadband seismic stations will be deployed across the Nashoba terrane in eastern Massachusetts, complementing currently available data in the area. Additionally, existing data from the Putnam terrane in eastern Connecticut, as sampled by the SEISConn array, will be used. While the top of the interpreted ductile extrusion zone is well constrained along the NW boundary of the Nashoba terrane, the SE part of the zone may have incorporated part of the Avalon terrane SE of the Nashoba terrane. New structural mapping and geochronology will be carried out in this part of the Avalon terrane to constrain the boundary of the ductile extrusion zone better. Combined new and existing structural, geochronological, and seismic imaging constraints will be used to test the channel flow hypothesis against alternative hypotheses, including thrust and normal faults, a positive flower structure, or a metamorphic core complex. The evolution of the Nashoba and Putnam terranes will then be placed in the overall context of the tectonic history of the SE New England Appalachians. Methods used and potential outcomes may provide new evidence for fundamental processes behind evolution of orogenic systems, enabling comparisons with modern systems (the Himalayas) as well as other ancient orogens (e.g., Canadian Cordillera) where channel flow and ductile extrusion have been proposed.Funding for this project is provided by NSF EAR Tectonics and Geophysics Programs.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

山带的形成是地球上发生的最重要的过程之一。山带会影响关键地球资源的分布，包括经济上重要的矿物质，石油和水。它们是板块构造的结果，沿着聚合板之间的边界。当山脉变得太高以至于无法稳定时，山带可能会横向扩展，或者由于重力的力量，材料可能会从皮带上“逃脱”。这种逃逸可能沿暴露在表面的断层发生，在该断层中，将材料从山带向侧面推开，或者仅通过材料从较高到较低的海拔崩溃而崩溃。在中部到深层的水平（在地面以下超过十公里处）以流体方式流动。在当今的山带（例如喜马拉雅山）中，这些类似液体的岩石可以从山皮带上喷出，无论是沿着表面还是完全沿着表面沿表面的通道下方。这些是有助于山带形成和修饰的重要过程，但它们仍然不完美地理解。具体而言，由于这些岩石流动区通常位于表面以下，因此在当今的山带系统中很难进行研究。该项目的目的是调查马萨诸塞州东部的古老流动区，该流量大约在420至3.6亿年前，如今已在表面部分暴露。地质技术将用于研究表面和地球物理成像技术的区域，以阐明地下几何形状。更好地理解这些流动区的形成将有助于我们更详细地了解古代和现代的山区建筑过程，这对我们对地球资源的分配方式有重要意义。该项目将涉及多学科研究，该研究将地质学家和地质物理学家汇集在一起​​，在阿巴拉契亚人工作，并与正在进行的民族和国际合作是协同作用。该项目将有助于对本科生和研究生的培训，重点是通过科罗拉多州矿业和耶鲁大学的各种课程培训从历史上未开发的小组的学生进行培训。一种综合的地球物理和地质方法将用于测试Appalachian Terranes，Nashoba Terrane ternane of Appalachian Terranes的通道流量和潜水延伸模型。通道流量是由于地壳增厚和压力梯度而导致的较弱的覆盖和下层地壳之间的弱，部分熔融的中层层的流动。表面的局部剥离可能会导致向表面的延展性延伸。该项目的目的不仅是为了进一步检验基于田间和地球体学数据的Nashoba地座演变的假设，而且还可以使用地球物理数据在地面下方的地质过去期间可视化岩石的延性流动。为此，将在马萨诸塞州东部的Nashoba Terrane上部署一个六个宽带地震站的紧密间隔阵列，并完成该地区当前可用的数据。此外，将使用由Seisconn阵列采样的来自康涅狄格州东部的Putnam Terrane的现有数据。虽然解释的延性挤压区的顶部沿着Nashoba Terrane的NW边界受到很好的约束，但该区域的SE部分可能已融合了Nashoba Terrane的Avalon Terrane SE的部分。新的结构映射和地质学将在Avalon Terrane的这一部分进行，以更好地限制延性扩展区的边界。新的和现有的结构，年代学和地震成像限制将用于测试通道流假设，以针对替代假设，包括推力和正常断层，正花结构或变质核心复合物。然后，Nashoba和Putnam Terranes的演变将被置于新英格兰阿巴拉契亚人SE构造历史的整体背景下。所使用的方法和潜在结果可能会为造山学系统进化背后的基本过程提供新的证据，从而可以与现代系统（喜马拉雅山）以及其他古老的Ogens（例如，加拿大Cordillera）进行比较使用基金会的智力优点和更广泛的影响标准，认为通过评估被认为是宝贵的支持。