Collaborative Research: Proterozoic Mountain Building and Collapse, Eastern Adirondacks, New York

合作研究：元古代造山与崩塌，东阿迪朗达克山脉，纽约

• 批准号: 1419876
• 负责人: Michael Williams
• 金额: $ 12.71万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-15 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1419876&HistoricalAwards=false
• 关键词: Collaborative; Research; Proterozoic; Mountain; Building

Rocks of the Adirondack Mountains of New York represent a large dome-shaped uplift of the Precambrian basement of North America. These rocks record the assembly and breakup of the supercontinent, "Rodinia" that formed approximately 1 billion years ago. The formation and dispersal of this continent may have played a role in the evolution of life on Earth, the evolution of climate and the production of a snowball Earth, and in the development of important economic resources, including Rare Earth Element deposits. New data are significantly changing our understanding of the history of the Adirondack uplift. A major period of mountain-building, the 1180 million year Shawinigan orogeny, was previously unrecognized in the region, and one challenge involves recognizing and distinguishing the effects of this tectonism compared to the 1050 Million year Ottawan orogeny that was previously thought to dominate the geology of this region. The latest stages in the geologic history of the Adirondacks involved intrusion of extensive granite ("Lyon Mountain granite") and the development of shear zones that were important in the collapse of the mountains and in the uplift of the basement rocks. This research will involve modern structural, petrologic, and geochronologic analysis to characterize the geologic and tectonic history of the eastern Adirondack region, and further our understanding of mid crustal processes during mountain building and collapse. This work represents a new collaboration between the University of Massachusetts and Castleton State College, a predominantly undergraduate state college nearly adjacent to the Adirondack field area. In addition to the PIs, the research team will consist of undergraduates from Castleton State College and a graduate student from the University of Massachusetts. The graduate student will serve as a mentor for undergraduates from Castleton and a link between the two institutions. The collaboration will provide an ideal base for field research during all seasons of the year and it will provide access for Castleton undergraduates to a predominantly undergraduate state college nearly adjacent to the Adirondack field area. In addition to the PIs, the research team will consist of undergraduates from Castleton State College and a graduate student from the University of Massachusetts. The graduate student will serve as a mentor for undergraduates from Castleton and a link between the two institutions. The collaboration will provide an ideal base for field research during all seasons of the year and it will provide access for Castleton undergraduates to a research-oriented university and to research equipment. Finally, the eastern Adirondack Mountains are a popular destination for hiking, camping, and vacations. Student researchers will work to develop outreach materials and programs about the geology of the spectacular northeastern Adirondack region.This research tests the hypothesis that there is a regionally extensive shear zone in the eastern Adirondacks in the vicinity of Whitehall, New York that accommodated the eastward unroofing of the Adirondack Mountains during orogenic collapse shortly after the culmination of the Ottawan orogenic event (ca. 1050 Ma). Preliminary in-situ monazite ages constrain the extensional shearing to 1050-1026 Ma, similar to those reported for the extensional movement on the Carthage-Colton shear zone in the NW Adirondacks. These data suggest that orogenic collapse following the Ottawan orogeny resulted in the formation of a two-sided metamorphic core complex or gneiss dome structure. This project will utilize in-situ high resolution monazite geochronology, in conjunction with detailed field mapping, structural and kinematic analysis, and metamorphic petrology in order to characterize the extent, kinematics, and timing of East Adirondack shearing and to integrate the shear zone into the overall tectonic history of the Adirondack Mountains. The Grenville orogen marks the culminating collision in the assembly of the supercontinent Rodinia. Post-collisional collapse of the Himalayan-scale Grenville orogen signaled the start of a new phase of rifting, passive margin development, and in the broadest sense, the Appalachian Wilson cycle. Major changes have been proposed in the character and age of tectonic events involved in the construction and collapse of the orogen. With the coming of Earthscope-US-Array and GeoPrisms it is critical to evaluate new models for this orogen that may have had a controlling influence on the geometry and character of the proto-Atlantic margin. The proposed research will involve detailed field mapping and structural/petrographic analysis in order to establish a chronologic framework for the development and overprinting relationships of fabrics and metamorphic mineral assemblages. Rocks related to each of the major stages of Adirondack orogenesis (Elsevirian, Shawinigan, AMCG plutonism, Ottawan, etc) are all in close proximity in the eastern Adirondacks. The project involves the use of thermobarometry and psuedosection analysis to delineate the Pressure-Temperature evolution of the crust during the orogenic events with particular focus on the late-stage shearing. A major portion of the work will involve in-situ monazite geochronology in order to place timing constraints on all parts of the history. Our ultimate goal is to place new constraints on the tectonic history of the Grenville Orogen, especially on the collapse and exhumation stages, and also to add to the evolving understanding of monazite behavior during metamorphism and deformation. This work will help to place the Adirondack massif within the context of gneiss domes and provide evidence about the role that this dome played in the collapse and exhumation of the orogen.

纽约阿迪朗达克山脉的岩石代表了北美前寒武纪基底的一个巨大的圆顶状隆起。这些岩石记录了大约10亿年前形成的超大陆“Rodinia”的组装和分裂。该大陆的形成和扩散可能在地球生命的进化、气候的演变和雪球地球的产生以及重要经济资源的开发（包括稀土元素矿床）中发挥了作用。新的数据正在显著改变我们对阿迪朗达克隆起历史的理解。一个主要的造山时期，即11.8亿年的沙维尼甘造山运动，在该地区以前没有被认识到，一个挑战是认识和区分这种构造作用的影响，与以前被认为主导该地区地质的10.5亿年的渥太华造山运动相比。阿迪朗达克山脉地质历史的最新阶段涉及到大面积花岗岩（“里昂山花岗岩”）的侵入和剪切带的发展，这些剪切带在山脉的崩塌和基底岩石的隆起中起着重要作用。这项研究将涉及现代结构，岩石学和地质年代学分析，以表征东部阿迪朗达克地区的地质和构造历史，并进一步了解造山和崩塌过程中的中地壳过程。这项工作代表了马萨诸塞州大学和卡斯尔顿州立学院之间的一项新的合作，卡斯尔顿州立学院是一所以本科为主的州立学院，几乎毗邻阿迪朗达克地区。除了PI外，研究小组还将由卡斯尔顿州立大学的本科生和马萨诸塞州大学的一名研究生组成。这位研究生将担任卡斯尔顿本科生的导师，并成为两所大学之间的纽带。这项合作将为一年四季的实地研究提供一个理想的基地，并将为卡斯尔顿的本科生提供进入一所以本科为主的州立大学的机会，该大学几乎毗邻阿迪朗达克地区。除了PI外，研究小组还将由卡斯尔顿州立大学的本科生和马萨诸塞州大学的一名研究生组成。这位研究生将担任卡斯尔顿本科生的导师，并成为两所大学之间的纽带。该合作将提供一个理想的基地，实地研究在一年中的所有季节，它将提供访问卡斯尔顿本科生到一个研究型大学和研究设备。最后，东部的阿迪朗达克山脉是徒步旅行，露营和度假的热门目的地。学生研究人员将致力于开发关于壮观的东北部阿迪朗达克地区地质的宣传材料和计划。这项研究测试了一个假设，即在纽约白厅附近的东部阿迪朗达克山脉存在一个区域性广泛的剪切带，该剪切带在奥塔万造山事件（约1000年）达到高潮后不久的造山崩塌期间容纳了阿迪朗达克山脉的向东去顶。1050 Ma）。 初步的原地独居石年龄限制拉伸剪切1050-1026马，类似于报告的西北阿迪朗达克山脉的迦太基-科尔顿剪切带上的拉伸运动。这些数据表明，奥塔万造山运动后的造山塌陷导致了一个双面变质核杂岩或片麻岩圆顶结构的形成。该项目将利用原地高分辨率独居石地质年代学，结合详细的野外测绘、结构和运动学分析以及变质岩石学，以确定东阿迪朗达克剪切的范围、运动学和时间，并将剪切带纳入阿迪朗达克山脉的整体构造历史。格伦维尔造山带标志着罗迪尼亚超大陆组装的最后碰撞。喜马拉雅规模的格伦维尔造山带的碰撞后崩塌标志着一个新的裂谷阶段的开始，被动边缘的发展，并在最广泛的意义上，阿巴拉契亚威尔逊旋回。在造山带的建造和崩塌过程中，构造事件的性质和时代发生了重大变化。随着Earthscope-US-Array和GeoPrisms的出现，评估可能对原始大西洋边缘的几何形状和特征产生控制影响的造山带新模型至关重要。拟议的研究将涉及详细的实地测绘和结构/岩相分析，以建立一个年代框架的发展和叠印关系的织物和变质矿物组合。与阿迪朗达克造山作用的每个主要阶段（埃尔塞维利安、沙维尼甘、AMCG深成岩作用、奥塔万等）有关的岩石都在阿迪朗达克东部附近。该项目涉及使用温压法和拟剖面分析来描绘造山事件期间地壳的压力-温度演化，特别侧重于后期剪切作用。这项工作的主要部分将涉及原地独居石地质年代学，以便对历史的各个部分进行时间限制。我们的最终目标是对格伦维尔造山带的构造历史，特别是对崩塌和折返阶段，提出新的限制，并增加对独居石在变质和变形过程中的行为的理解。这项工作将有助于把阿迪朗达克山脉的片麻岩圆顶的背景下，并提供有关的作用，这个圆顶造山带的崩溃和折返的证据。