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.

山脉的形成是地球上最重要的过程之一。山区地带影响着地球主要资源的分布，包括具有重要经济意义的矿产、石油和水。它们是板块构造运动的结果，沿着会聚板块之间的边界形成。当山脉变得太高而不稳定时，山脉带可能会横向扩张，或者由于重力的作用，物质可能会从山脉带“逃逸”。这种逃逸可能发生在沿着暴露在地表的断层上，在那里物质被推离山脉带的侧面，或者仅仅是由于物质从较高的海拔向较低的海拔坍塌。在中地壳至地壳深部（地表以下10公里以上），岩石以类似流体的方式流动。在现今的山脉地带，如喜马拉雅山脉，这些流体状的岩石可以从山脉地带喷出，要么喷向地表，要么沿着沿着扁平通道完全喷到地表以下。这些都是有助于山脉形成和改变的重要过程，但人们对它们的认识仍然不够完善。具体来说，由于这些岩石流动带通常在地表以下，因此很难在现今的山区带系统中进行调查。该项目的目的是调查马萨诸塞州东部的一个古老的流动区，该流动区形成于约4.2亿至3.6亿年前，今天部分暴露在地表。地质技术将用于调查该区域的表面和地球物理成像技术，以阐明地下几何形状。更好地了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造山过程，对我们了解地球资源如何分布具有重要意义。该项目将涉及多学科研究，汇集了在阿巴拉契亚山脉工作的地质学家和地质学家，并与正在进行的国家和国际合作协同。该项目将有助于培养本科生和研究生，重点是通过科罗拉多矿业学院和耶鲁大学的各种方案，培养来自历史上未开发群体的学生。综合地球物理和地质方法将用于测试阿巴拉契亚山脉之一，东南新英格兰的纳什巴山脉的通道流动和韧性挤出模型。水道流是由于地壳增厚和压力梯度，在较强的上覆地壳和下覆地壳之间的较弱的、部分熔融的中下地壳层的流动。地表局部剥蚀可能导致向地表的韧性挤出。该项目的目的不仅是根据实地和地质年代学数据进一步检验关于纳什巴河演化的假设，而且还利用地球物理数据可视化地表以下地质过去期间岩石的韧性流动。为此，将在马萨诸塞州东部的纳什巴河上部署一个由六个宽带地震台站组成的密集阵列，以补充该地区目前可用的数据。此外，将使用由SEISConn阵列采样的康涅狄格州东部普特南湖的现有数据。虽然解释的韧性挤出带的顶部沿Nashoba断层的西北边界沿着受到很好的约束，但该带的东南部分可能已合并了Nashoba断层的Avalon断层东南部分。将在阿瓦隆盆地的这一部分进行新的构造测绘和地质年代学研究，以更好地限制韧性挤出带的边界。结合新的和现有的结构，地质年代学和地震成像的限制，将被用来测试通道流假说对替代假设，包括逆冲断层和正断层，一个积极的花状结构，或变质核杂岩。纳什巴和普特南山脉的演化将被置于东南部新英格兰阿巴拉契亚山脉构造历史的整体背景下。所使用的方法和潜在的结果可能为造山系统演化背后的基本过程提供新的证据，使其能够与现代系统（喜马拉雅山）以及其他古代造山带（例如，加拿大科迪勒拉山脉），其中通道流和韧性挤出已被提出。该项目的资金是由美国国家科学基金会地质构造和地球物理计划提供。该奖项反映了美国国家科学基金会的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。