Collaborative Research: Arc plutonism along the Denali Fault, Alaska: Possible fault controls on incremental magma transport and assembly along a long-lived strike-slip fault

合作研究：阿拉斯加德纳利断层沿线的弧岩成体作用：断层可能控制沿长期走滑断层增量岩浆输送和聚集

• 批准号: 2121178
• 负责人: Sarah Roeske
• 金额: $ 18.56万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2121178&HistoricalAwards=false
• 关键词: Collaborative; Research; Arc; plutonism; along

Volcanoes above subduction zones almost always appear as an irregular or curvy line on the surface of the earth. Scientists have a general idea of why these “arc” volcanoes, such as the Cascade arc, create linear chains, but whether vertical faults that penetrate deep in the crust control their specific location, composition, and potential eruptive volume is a subject of much debate. Volcanoes erode quickly so a study of their large magmatic roots, called plutons, will provide a more spatially and temporally complete record to better understand whether vertical faults provide direct conduits between deeper crust, where magma is produced, and the upper crust, where magma forms a reservoir for volcanic eruptions. The Alaska Range has been shaped by subduction and translation for tens of millions of years, as southern Alaska moves westward relative to the Alaskan interior along the active Denali fault, which extends for over 2000 km and ruptured during a magnitude (Mw) 7.9 earthquake in 2002. A suite of 45-35-million-year-old arc plutons are spatially associated with the Denali fault. This proposed research will study the physical relationships of melt transport along a long-lived strike-slip fault (the Denali fault) to test how continental-scale structures may control the rates of transport of melt to the surface, geometry of pluton growth, and magma evolution. In addition, the Principal Investigators will try to use plutons analyzed during this study to provide better constraints on the long-term slip rate of the Denali fault. The project will include undergraduate students, graduate students, and professors from public universities that have diverse undergraduate programs. The tallest peak in North America, Denali (formerly Mt. McKinley), includes arc plutons of this study that are cut by the Denali fault. Outreach efforts will include developing a social media presence for the Denali fault and updating public-science dissemination exhibits at the Museum of the North in Fairbanks and Denali National Park. We will develop curriculum for the GeoForce learning community, a STEM-focused organization focused on engaging rural and first-generation students from Alaska.Crustal-scale structures are often linked to the transport of lower crustal melts through the upper crust. However, the mechanism(s) by which and if melt is transported along active strike-slip faults is still an ongoing problem in the petrology community. Distinguishing disparate mechanism(s) or combinations therein is critical for unraveling the complex interplay of granitoid petrogenesis in the upper crust, mass and thermal mantle-surface communication, and how structural processes are manifested in a petrologic system. The Denali Fault is a classic long-lived orogenic ( 2000 km) dextral strike-slip fault system with 400 km of lateral offset associated with, and perhaps localizing, arc plutonism for over ~70 My. This research project will test the hypothesis that crustal-scale faults can facilitate melt transport and pluton construction that results in systematic temporal-spatial geochemical and petrophysical patterns linked to strike-slip motion. The research will include collecting a fault-relative petrochemical and petrophysical dataset on a suite of Eocene plutons on both sides and along a ~350 km transects of the Denali Fault to evaluate how magmatic processes are manifested at the spatial and temporal scales relevant to magma transport and emplacement along an orogenic-scale strike slip fault. Field characterization combined with whole rock major and trace element geochemistry, zircon U-Pb geochronology, and O isotopic tracer analysis will be applied with these fundamental objectives: 1) identify petrographic, geochemical, isotopic, and/or structural gradients and 2) interpret results as they relate to pluton geometry as well as to the Denali Fault. In addition to testing kinematic controls on granitoid petrogenesis, these data will resolve a long-standing problem in Cordilleran geology, by evaluating a potential Denali Fault piercing point. Preliminary data indicate a possible pluton correlation may exist across the Denali Fault that would indicate an average slip rate of 8-10 mm/yr since 40 Ma, similar to the present-day dextral slip rate in this section of the fault. Data from this study will provide a recipe for distinguishing actually offset plutons from a suite of similar intrusive bodies preferentially emplaced along a fault system and help explain temporal-spatial petrochemical and petrophysical variability during continental arc assembly along strike-slip faults.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.

俯冲带上方的火山几乎总是以不规则或弯曲的线条出现在地球表面。科学家们对这些“弧”火山（如喀斯喀特弧）为什么会形成线性链有一个大致的概念，但穿透地壳深处的垂直断层是否控制了它们的具体位置，成分和潜在的喷发量是一个备受争议的话题。火山侵蚀速度很快，因此对它们的大型岩浆根源（称为侵入岩）的研究将提供一个在空间和时间上更完整的记录，以更好地了解垂直断层是否在产生岩浆的更深地壳和岩浆形成火山爆发水库的上地壳之间提供直接管道。阿拉斯加山脉经过数千万年的俯冲和平移而形成，因为阿拉斯加南部相对于阿拉斯加内陆沿着活动的迪纳利断层向西移动，该断层延伸超过2000公里，并在2002年的7.9级地震中破裂。一套4500 - 3500万年的弧岩体在空间上与德纳里断层有关。 这项拟议的研究将研究熔体运输沿着一个长期的走滑断层（德纳里断层）的物理关系，以测试如何大陆规模的结构可能控制熔体运输到表面的速度，岩体生长的几何形状和岩浆演化。此外，主要研究人员将尝试使用在本研究期间分析的岩体，以提供对德纳里断层长期滑动速率的更好约束。该项目将包括来自公立大学的本科生，研究生和教授，这些大学有不同的本科课程。北美最高峰迪纳利峰（Denali），原Mt.麦金利），包括本研究中被Denali断层切割的弧深圳湾。外联工作将包括为德纳利断层开发社交媒体，并更新费尔班克斯北部博物馆和德纳利国家公园的公共科学传播展览。我们将为GeoForce学习社区开发课程，这是一个专注于STEM的组织，专注于吸引来自阿拉斯加的农村和第一代学生。地壳尺度结构通常与下地壳熔体通过上地壳的运输有关。然而，熔体是否沿沿着活动的走滑断层运移以及熔体的运移机制仍是岩石学研究中的一个难题。区分不同的机制（S）或其中的组合是至关重要的揭示复杂的相互作用的花岗岩类岩石在上地壳，质量和热地幔表面的通信，以及如何在岩石学系统中表现出的结构过程。德纳里断层是一个典型的长寿造山（2000公里）右旋走滑断层系统与400公里的横向偏移相关，并可能本地化，弧深圳湾超过70米。该研究项目将检验这样一种假设，即地壳规模的断层可以促进熔体输送和岩体构造，从而产生与走滑运动有关的系统的时空地球化学和岩石物理模式。这项研究将包括收集一套始新世岩体两侧和沿着迪纳利断层约350公里横断面的断层相关岩石化学和岩石物理数据集，以评价岩浆过程如何在空间和时间尺度上表现出来，与岩浆运输和沿沿着造山尺度走滑断层就位有关。现场表征结合全岩主要和微量元素地球化学、锆石U-Pb地质年代学和O同位素示踪剂分析将应用于这些基本目标：1）确定岩相学、地球化学、同位素和/或结构梯度，2）解释结果，因为它们与岩体几何形状以及德纳里断层有关。除了测试花岗岩类岩石成因的运动学控制，这些数据将解决一个长期存在的问题，在科迪尔地质，通过评估潜在的德纳里断层穿刺点。初步数据表明，可能存在的岩体相关性可能存在于整个德纳里断层，这将表明自40 Ma以来的平均滑动速率为8-10 mm/年，类似于现今断层这一部分的右旋滑动速率。这项研究的数据将提供一个方法，用于区分实际偏移的岩体与一套优先沿着断层系统侵位的类似侵入体，并有助于解释沿着走向大陆弧组装期间的时空石化和岩石物理变化。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查进行评估，被认为值得支持的搜索.