Structural, metamorphic, and thermal evolution of the Brooks Range (Alaska) metamorphic belts: implications for formation-exhumation of high-pressure rocks and Arctic tectonic evol

布鲁克斯山脉（阿拉斯加）变质带的结构、变质和热演化：对高压岩石形成折返和北极构造演化的影响

• 批准号: 2019525
• 负责人: James Vogl
• 金额: $ 22万
• 依托单位: University of Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-12-01 至 2024-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2019525&HistoricalAwards=false
• 关键词: Structural; metamorphic; thermal; evolution; Brooks

With a length of over 600 km, the Schist belt in the Brooks Range of northern Alaska is one of the largest high-pressure metamorphic terranes in the world and shares many characteristics with other high-/ultra-high- metamorphic rocks around the world. This study is focused on documenting the deformational, metamorphic, and thermal histories of the Schist belt and adjacent lower pressure metamorphic rocks to test hypotheses related to two groups of questions. (1) How are high-pressure rocks exhumed to the Earth’s surface? Buoyant continental lithospheric plates may be pulled into subduction zones by sinking of the attached dense oceanic lithosphere at subduction zones, providing a simple explanation for deep tectonic burial and associated high-pressure metamorphism in continental rocks. However, the processes by which these high-pressure rocks are brought back up to the earth’s surface remain poorly understood. (2) The Brooks Range, the rest of the northern Alaska, and Chukotka are widely believed to have rotated about 66° anti-clockwise away from the Canadian Arctic Islands during formation of the Canada Basin (Arctic Ocean). It remains unclear as to what geologic events (e.g., continental subduction and high-pressure metamorphism, collision, extension, basin formation), if any, in the Brooks Range are dynamically linked to rotational basin opening. Furthermore, it is unclear as to how this geometrical style of basin opening is accommodated along the strike of the of the ca. 3000 km long continental land mass from northeastern Alaska to Chukotka. This project will provide financial support and training of a Ph.D. student, a M.Sc. student, and multiple undergraduates in STEM fields, potentially including women and underrepresented groups. The students will gain experience in field mapping, as well as a variety of analytical laboratory techniques in facilities with experts at two universities. Graduate students will be involved in outreach through creation of teaching materials focused on Arctic geology that will be distributed to Alaska schools through collaboration with the Alaska Division of Geological & Geophysical Surveys. Through an increased understanding of Arctic geology, this study will provide an improved framework for economic development of resources as the Arctic region opens for exploration in the coming decade.Jurassic(?)-Cretaceous convergence between a passive margin and the oceanic Angayucham terrane produced the Brooks Range orogen (northern Alaska), which includes a fold-thrust belt and two metamorphic belts: the blueschist/eclogite Schist belt and the high-pressure greenschist Central belt. However, many key aspects of the structural, metamorphic, and thermal histories are lacking for these metamorphic belts, resulting in diverse models for exhumation of the high-pressure rocks, and the tectonic evolution of both the Brooks Range and greater Arctic region. In this study we will use field and analytical techniques to document the structural, metamorphic, and thermal evolution of both belts to test models in three interrelated categories. (1) The researchers will test models for the highly debated relationships regarding the timing and geodynamic significance of normal-sense structures on the south flank of the Brooks Range, and the tectonic setting of flanking basins. The work will place kinematic and age constraints on tectono-thermal events, particularly in during the Aptian-Albian, a key time of important change in north Alaska and the adjacent Arctic realm. (2) The researchers will test models for the formation and exhumation of high-pressure rocks, with a focus on the role of buoyancy-driven exhumation models. (3) The Brooks Range and the rest of the Arctic Alaska – Chukotka microplate is believed to have rotated about 66° anti-clockwise away from the Canadian Arctic Islands, resulting in the formation of the Canada Basin. It remains unclear as to what events (e.g., continental subduction and high-P metamorphism, collision, extension, basin formation), if any, in the Brooks Range are dynamically linked to basin opening. Furthermore, there is debate regarding how this geologically unprecedented geometrical basin opening is accommodated along the strike of the of the ca. 3000-km-long continental land mass of the Arctic Alaska – Chukotka microplate. Improved timing constraints for Brooks Range tectonic events will address these issues and test specific models.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.

阿拉斯加北部布鲁克斯山脉的片岩带长度超过600公里，是世界上最大的高压变质岩带之一，与世界上其他高/超高变质岩具有许多共同特征。本研究的重点是记录片岩带和邻近低压变质岩的变形、变质和热历史，以检验与两组问题相关的假设（1）高压岩石如何。浮力大陆岩石圈板块可能会通过俯冲带上附着的致密海洋岩石圈的下沉而被拉入俯冲带，这为大陆岩石的深部构造埋藏和相关的高压变质作用提供了简单的解释。人们对这些高压岩石如何被带回地球表面仍知之甚少。 (2) 人们普遍认为，布鲁克斯山脉、阿拉斯加北部的其他地区和楚科奇半岛是通过这种方式返回地球表面的。在加拿大盆地（北冰洋）形成期间，从加拿大北极群岛逆时针旋转了约66°。目前尚不清楚发生了哪些地质事件（例如大陆俯冲和高压变质作用、碰撞、伸展、盆地形成）。 ），如果有的话，在布鲁克斯山脉与旋转盆地开口动态相关。此外，目前还不清楚这种几何类型的盆地开口是如何沿着约的走向适应的。该项目从阿拉斯加东北部到楚科奇半岛长达 3000 公里，将为一名博士生、一名硕士生和多名本科生（可能包括女性和弱势群体）提供培训。将在两所大学的专家的帮助下获得野外测绘经验以及各种分析实验室技术，研究生将通过制作以北极地质学为重点的教材来参与推广活动，这些教材将通过与阿拉斯加的学校合作分发给阿拉斯加的学校。阿拉斯加地质与地球物理调查部。通过加深对北极地质的了解，随着北极地区在未来十年开放勘探，这项研究将为资源经济开发提供一个改进的框架。侏罗纪（？）-白垩纪被动边缘之间的融合海洋安加尤查姆地体产生了布鲁克斯山脉造山带（阿拉斯加北部），其中包括一个褶皱冲断带和两个变质带：蓝片岩/榴辉岩片岩带和然而，这些变质带缺乏构造、变质和热历史的许多关键方面，导致高压岩石的折返和布鲁克斯山脉的构造演化存在多种模型。在这项研究中，我们将使用高度现场和分析技术来记录这两个带的结构、变质和热演化，以测试三个相互关联的类别的模型（1）研究人员将测试有争议的模型。这项工作将对布鲁克斯山脉南侧的正常构造的时间和地球动力学意义以及侧翼盆地的构造背景进行研究，特别是在阿普第-阿尔布阶期间，对构造热事件施加运动学和年龄限制。 ，阿拉斯加北部和邻近北极地区发生重要变化的关键时期（2）研究人员将测试高压岩石形成和折返的模型，重点关注高压岩石的作用。 (3) 布鲁克斯山脉和北极阿拉斯加-楚科奇微板块的其余部分被认为已从加拿大北极群岛逆时针旋转了约 66°，从而形成了加拿大盆地。目前尚不清楚布鲁克斯山脉中的哪些事件（例如大陆俯冲和高磷变质作用、碰撞、伸展、盆地形成）（如果有的话）与盆地开放动态相关。关于如何沿着北极阿拉斯加-楚科奇微板块约 3000 公里长的大陆块的走向容纳这一地质上前所未有的几何盆地开口的争论将解决这些问题并测试布鲁克斯山脉构造事件的时间限制。该奖项反映了 NSF 的法定使命，并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，被认为值得支持。