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.

阿拉斯加北方布鲁克斯山脉的片岩带长600多公里，是世界上最大的高压变质岩带之一，与世界上其他高/超高变质岩有许多共同特征。这项研究的重点是记录变形，变质，和热历史的片岩带和邻近的低压变质岩测试有关的两组问题的假设。(1)高压岩石是如何被挖掘到地球表面的？浮力大陆岩石圈板块可能被俯冲带附近的致密大洋岩石圈下沉拉入俯冲带，这为大陆岩石的深构造埋藏和相关的高压变质作用提供了一个简单的解释。然而，这些高压岩石被带回地球表面的过程仍然知之甚少。(2)布鲁克斯山脉、阿拉斯加北方的其余部分和楚科奇被广泛认为在加拿大海盆（北冰洋）形成期间逆时针旋转了大约66°，远离加拿大北极群岛。目前还不清楚是什么地质事件（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打开有着动态的联系。此外，尚不清楚盆地开口的这种几何样式如何沿沿着CA的走向适应。3000公里长的大陆块，从阿拉斯加东北部到楚科奇。该项目将提供财政支持和培养一名博士。学生，一名硕士学生和多名STEM领域的本科生，可能包括妇女和代表性不足的群体。学生将获得实地测绘的经验，以及在两所大学的专家设施中的各种分析实验室技术。研究生将通过与阿拉斯加地质地球物理调查司合作，编写以北极地质为重点的教材，分发给阿拉斯加的学校，从而参与外联活动。通过对北极地质的进一步了解，这项研究将为未来十年北极地区的勘探开放提供一个更好的资源经济开发框架。白垩纪被动边缘和大洋Angayucham山脉之间的会聚产生了布鲁克斯山脉造山带（北方阿拉斯加），其中包括一个褶皱-冲断带和两个变质带：蓝片岩/榴辉岩片岩带和高压绿片岩中央带。然而，许多关键方面的结构，变质和热历史缺乏这些变质带，导致不同的模式折返的高压岩石，构造演化的布鲁克斯范围和大北极地区。在这项研究中，我们将使用现场和分析技术来记录这两个带的结构，变质和热演化测试模型在三个相互关联的类别。(1)研究人员将测试关于布鲁克斯山脉南翼正常意义结构的时间和地球动力学意义以及侧翼盆地构造背景的高度争议关系的模型。这项工作将对构造热事件进行运动学和年龄限制，特别是在Aptian-Albian期间，这是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，重点是浮力驱动折返模型的作用。(3)据信，布鲁克斯山脉和阿拉斯加-楚科奇微板块的其余部分逆时针旋转了约66°，远离加拿大北极群岛，导致了加拿大盆地的形成。目前还不清楚是什么事件（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，在布鲁克斯山脉是动态地与盆地打开。此外，关于这一地质学上前所未有的几何盆地开口如何沿沿着该地区的走向被容纳，也存在争议。3000公里长的北极阿拉斯加大陆块-楚科奇微板块。改进布鲁克斯山脉构造事件的时间限制将解决这些问题并测试特定的模型。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。