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在地球表面出现。科学家对为什么这些“弧形”火山（例如级联电弧）产生线性链有一个普遍的概念，但是在地壳深处控制着它们的特定位置，组成和潜在的喷发量是否是许多争论的主题。 Volcanoes erodes quickly so a study of their large magmatic roots, called plutons, 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弧岩通常与Denali断层有关。这项拟议的研究将研究沿长寿命滑移断层（Denali断层）熔体转运的物理关系，以测试连续尺度结构如何控制熔体向表面的运输速率，plut子生长的几何形状和Magma Evolution。此外，主要研究人员将尝试使用本研究中分析的岩体，以更好地限制Denali断层的长期滑动速率。该项目将包括本科生，研究生以及拥有潜水本科课程的公立大学的教授。北美最高的山峰是丹纳利（以前是麦金莱山），其中包括这项研究的弧形岩石，这些弧形被Denali断层切割。推广工作将包括为Denali的缺点开发社交媒体，并在Fairbanks和Denali国家公园的北部博物馆更新公共科学传播展览。我们将为Geoforce Learning社区开发课程，这是一个以STEM为重点的组织，致力于吸引来自阿拉斯加的农村和第一代学生。Crustal尺度结构通常与下层地壳通过下层地壳运输。但是，在岩石学界，沿主动滑移断层运输熔体的机制和是否沿主动滑移断层运输的机制仍然是一个持续的问题。区分不同的机制或其中的组合对于揭示上皮，质量和热地幔表面通信中花岗岩岩发生的复杂相互作用以及在岩石系统中如何表现的结构过程。 Denali断层是经典的长期造型（2000 km）右旋滑动断层系统，其侧向偏移400 km，并且可能本地化，弧形plutonism，以超过70 my的速度。该研究项目将检验以下假设：地壳规模的断层可以促进熔体运输和岩体结构，从而导致系统的临时空间地球化学和岩石物理模式与滑滑运动有关。这项研究将包括在双方以及沿Denali断层的约350公里的二世型岩石上收集相关性的石化和石油物理数据集，以评估与岩浆和临时尺度相关的岩浆过程与Magma Transport and Emplacement cys oter Olplacement沿着摩根式的尺度相关。现场表征与全摇滚元素和痕量元素地球化学，锆石U-PB地质学和O同位素示踪剂分析相结合，将与这些基本目标相结合：1）确定岩石学，地球化学，同位素和/或结构梯度以及2）与Prouton GeemeTry以及Denali的相关结果，并解释结果。除了测试花岗岩岩发生的运动学控制外，这些数据还将通过评估潜在的Denali断层穿孔点来解决Cordilleran地质的长期问题。初步数据表明，在Denali断层中可能存在可能存在plut子相关性，这表明自从40 mA以来的平均滑移速率为8-10 mm/yr，类似于当前故障这一部分的右旋滑动速率。这项研究的数据将提供一个配方，以区分实际抵消岩石与沿断层系统优先放置的类似侵入型物体的套件，并有助于解释沿着沿行动 - 滑动奖励的连续弧形组装过程中的临时空间石化和岩石物理变异性，这些奖项反映了NSF的法定任务，并通过评估了构成的范围。