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地下室的一个巨大的穹顶状隆起。这些岩石记录了大约10亿年前形成的超级大陆罗迪尼亚的组装和解体过程。这块大陆的形成和扩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藏在内的重要经济资源的开发中发挥了作用。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1.18亿年的沙维尼根造山作用，以前在该地区没有被认识到，一个挑战是识别和区分这一构造运动的影响，与之前被认为主导该地区地质的1.05亿年的奥塔万造山作用相比。阿迪朗达克山脉地质史的最新阶段包括广泛的花岗岩(“里昂山脉花岗岩”)的侵入和剪切带的发展，这些剪切带在山脉的坍塌和基底岩石的抬升中起着重要作用。这项研究将包括现代构造、岩石学和地质年代学分析，以刻画阿迪朗达克东部地区的地质和构造历史，并加深我们对造山和崩塌过程中地壳过程的理解。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合作，卡斯尔顿州立学院是一所主要是本科生的州立学院，几乎毗邻阿迪朗达克田野地区。除了PI，研究团队还将包括卡斯尔顿州立学院的本科生和马萨诸塞大学的一名研究生。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。这项合作将为一年中所有季节的实地研究提供理想的基础，它将为卡斯尔顿本科生提供进入一所几乎毗邻阿迪朗达克田野地区的以本科生为主的州立大学的途径。除了PI，研究团队还将包括卡斯尔顿州立学院的本科生和马萨诸塞大学的一名研究生。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。这项合作将为一年中所有季节的实地研究提供一个理想的基础，它将为卡斯尔顿大学的本科生提供进入研究型大学和获得研究设备的机会。最后，东部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扩展材料和项目。这项研究检验了这样的假设，即在纽约怀特霍尔附近的阿迪朗达克东部存在一个地区性广泛的剪切带，在奥塔万造山事件(约1050 Ma)达到顶峰后不久的造山坍塌期间，该剪切带容纳了阿迪朗达克山脉向东剥落。独居石的初步原位年龄将伸展剪切力限制在1050-1026 Ma，这与已报道的阿迪朗达克西北部迦太基-科尔顿剪切带上的伸展运动相似。这些数据表明，奥塔万造山运动后的造山塌陷导致了双侧变质核杂岩或片麻岩穹隆结构的形成。该项目将利用现场高分辨率独居石年代学，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的程度、运动学和时间，并将该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的碰撞达到顶峰。喜马拉雅规模的格伦维尔造山带的碰撞后坍塌标志着裂谷作用的新阶段的开始，被动边缘发展，从最广泛的意义上讲，是阿巴拉契亚-威尔逊旋回。造山带的建造和坍塌所涉及的构造事件的性质和时代发生了重大变化。随着地球镜-US-阵列和GeoPrisms的到来，评估这一造山带的新模型是至关重要的，这些模型可能已经对原大西洋边缘的几何和特征产生了控制影响。拟议的研究将涉及详细的野外测绘和构造/岩石学分析，以便为组构和变质矿物组合的发展和叠印关系建立一个年代学框架。与阿迪朗达克造山作用各主要阶段(埃尔塞维里期、沙维尼根期、AMCG深成期、奥塔万期等)相关的岩石在阿迪朗达克东部都非常接近。该项目涉及利用温压测量和假剖分分析来描绘造山事件期间地壳的压力-温度演化，特别是后期剪切作用。这项工作的一大部分将涉及独居石地质年代学，以便对历史的所有部分施加时间限制。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的构造历史施加新的限制，并增加对独居石在变质和变形过程中行为的演变的理解。这项工作将有助于将阿迪朗达克地块置于片麻岩穹隆的背景中，并为该穹隆在造山带坍塌和折返中所起的作用提供证据。

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.