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

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“罗迪尼亚”的聚集和分裂。这块大陆的形成和分散可能在地球上生命的进化、气候的演变和雪球地球的产生，以及包括稀土元素矿床在内的重要经济资源的开发中发挥了作用。新的数据显著地改变了我们对阿迪朗达克隆起历史的理解。一个重要的造山时期，即11亿8千万年的沙文尼根造山运动，以前在该地区没有被认识到，其中一个挑战是认识和区分这种构造运动的影响，将其与之前被认为主导该地区地质的10亿5千万年的渥太华造山运动进行比较。阿迪朗达克地质历史的最后阶段包括广泛的花岗岩（“里昂山花岗岩”）的侵入和剪切带的发育，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构造、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，并进一步了解山脉形成和崩塌期间的中期地壳过程。这项工作代表了马萨诸塞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主要的本科州立学院，靠近阿迪朗达克地区。除了pi之外，研究团队还将由卡斯尔顿州立学院的本科生和马萨诸塞州大学的一名研究生组成。该研究生将担任卡斯尔顿大学本科生的导师，并成为两所大学之间的纽带。这项合作将为全年的实地研究提供一个理想的基地，它将为卡斯尔顿的本科生提供进入一所主要是本科生的州立学院的机会，该学院几乎毗邻阿迪朗达克地区。除了pi之外，研究团队还将由卡斯尔顿州立学院的本科生和马萨诸塞州大学的一名研究生组成。该研究生将担任卡斯尔顿大学本科生的导师，并成为两所大学之间的纽带。这项合作将为全年的实地研究提供一个理想的基地，它将为卡斯尔顿大学的本科生提供进入研究型大学和研究设备的机会。最后，东部的阿迪朗达克山脉是远足、露营和度假的热门目的地。学生研究人员将致力于开发有关壮观的东北部阿迪朗达克地区地质的宣传材料和项目。这项研究验证了一个假设，即在渥太华造山事件（约1050 Ma）达到顶峰后不久，在纽约州怀特霍尔附近的阿迪朗达克山脉东部存在一个区域性广泛的剪切带，该剪切带容纳了阿迪朗达克山脉在造山崩塌期间的向东拆顶。初步的原位独居石年龄限制了伸展剪切作用在1050-1026 Ma，与西北阿迪朗达克地区迦太基-科尔顿剪切带的伸展运动相似。这些资料表明，渥太华造山运动后的造山崩塌形成了双面变质核杂岩或片麻岩穹丘构造。该项目将利用现场高分辨率的单叠石年代学，结合详细的野外测绘、构造和运动学分析以及变质岩石学，以表征东阿迪朗达克剪切作用的范围、运动学和时间，并将剪切带整合到阿迪朗达克山脉的整体构造历史中。格伦维尔造山带标志着罗迪尼亚超大陆组合的最终碰撞。喜马拉雅规模的格伦维尔造山带碰撞后的崩塌标志着裂谷作用的新阶段的开始，被动边缘发育，从最广泛的意义上说，就是阿巴拉契亚威尔逊旋回。在造山带构造和崩塌过程中所涉及的构造事件的性质和时代方面，提出了重大的变化。随着地球镜- us - array和地球活动的到来，评估这个造山带的新模式是至关重要的，它可能对原大西洋边缘的几何形状和特征产生了控制影响。拟议的研究将包括详细的实地测绘和构造/岩石学分析，以便为构造和变质矿物组合的发展和叠印关系建立一个年代学框架。与阿迪朗达克各主要造山阶段（Elsevirian、Shawinigan、AMCG深部成矿作用、Ottawan等）相关的岩石在阿迪朗达克东部都很接近。该项目包括使用热气压计和伪剖面分析来描绘造山活动期间地壳的压力-温度演化，特别关注后期剪切。这项工作的主要部分将涉及原位独居石地质年代学，以便对历史的所有部分进行时间限制。我们的最终目标是对格伦维尔造山带的构造历史，特别是在崩塌和挖掘阶段，提出新的限制，并增加对变质和变形过程中独居石行为的不断发展的理解。这项工作将有助于将阿迪朗达克地块置于片麻岩穹窿的背景下，并提供证据证明这个穹窿在造山带的崩塌和挖掘中所起的作用。

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.