EAR-PF: Experimental Constraints on Dating Ductile Deformation with Titanite

板块构造学是解释几乎所有地球过程的基本理论，该理论认为地球最外层的部分被划分为移动的刚性板块。这些构造板块的运动导致岩石破裂并改变形状。地球深处岩石的这种破裂和形状变化(也称为变形)建造了山脉并产生了地震。为了更好地了解山脉是如何建造的，为什么会发生地震，地球科学家必须能够准确地确定这些过程发生的时间和速度。要做到这一点，地球科学家需要一种方法或工具来确定变形的日期(即确定过去发生变形的时间)。尽管它很重要，但没有直接的方法来确定变形的日期。这个项目的目标是开发一种工具，通过对一种名为钛铁矿的矿物进行实验室实验，来确定变形的日期。地球科学家将能够将这一项目的结果应用于自然界中的岩石，以确定过去发生变形的时间和速度，从而填补地球科学研究中的一个基本知识空白。此外，由于地球科学是最不多样的STEM领域之一，这项工作还旨在通过与K-12学生的外联活动以及通过指导研究项目中代表性不足的本科生来提高这一科学分支学科的多样性、公平性和包容性。了解构造过程的基本原理，包括板块边界起始、所有地壳水平的形变反馈和应变分配，在一定程度上依赖于限制地壳变形的时间、持续时间和速率。尽管它意义重大，但直接测定韧性变形日期的能力在地球科学研究中仍然是一个突出的挑战。矿物钛铁矿(化学式为CaTiSiO5)非常适合测定地壳形变的年龄。然而，在剪切带中重结晶钛铁矿的过程繁多，这使得评估如何利用天然岩石将日期与变形联系起来具有挑战性。该项目的目标是利用高压、高温钛合金变形实验来开发一种新的工具来确定高温(即400°C)变形的日期。变形实验的产品将使用各种电子显微镜技术进行表征，包括电子背散射衍射(以量化变形微结构并确定适应应变的变形机制)和X射线映射(以确定在实验期间形成的成分分带)。这些特征与U-Pb年龄(结合二次离子质谱仪和原子探针层析)之间的关系将揭示变形微结构的发展如何影响钛铁矿中的U-Pb系统。这些综合数据集将为利用自然变形岩石中的钛铁矿测定地壳变形的最佳做法提供信息，从而在地球科学研究方面取得革命性的进展。这项工作的更广泛的影响将集中在通过与面向青年的组织的外联活动以及通过指导研究项目中代表不足的群体的本科生来改善地球科学的多样性、公平性和包容性。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Plate tectonics - the theory that the outermost later of Earth is divided into rigid plates that move - is the fundamental theory that explains nearly all Earth processes. The motion of these tectonic plates causes rocks to break and change shape. This breaking and shape change (also known as deformation) of rocks deep within the Earth builds mountains and produces earthquakes. To better understand how and why mountains are built and earthquakes occur, Earth scientists must be able to pinpoint when and how fast these processes happen. Doing so requires a method or tool that Earth scientists can use to date deformation (i.e., to determine when deformation has occurred in the past). Despite its importance, there is no straightforward way to date deformation. The goal of this project is to develop a tool to date deformation using laboratory experiments on a mineral called titanite. Earth scientists will be able to apply the results of this project to rocks in nature to determine when and how fast deformation has happened in the past, thereby filling a fundamental knowledge gap in Earth science research. In addition, as the Earth sciences are among the least diverse STEM fields, this work also aims to improve the diversity, equity, and inclusion of this scientific subdiscipline through outreach activities with K–12 students and by mentoring undergraduate students from underrepresented groups in research projects.Understanding the fundamentals of tectonic processes, including plate boundary initiation, deformation feedbacks at all crustal levels, and strain partitioning, relies in part on constraining the timing, duration, and rates of crustal deformation. Despite its significance, the ability to directly date ductile deformation remains an outstanding challenge in Earth science research. The mineral titanite (chemical formula CaTiSiO5) is well-suited to date crustal deformation. However, the multitude of processes that recrystallize titanite in shear zones makes it challenging to assess how to tie dates to deformation using natural rocks. The goal of this project is to use high-pressure, high-temperature titanite deformation experiments to develop a new tool to date high-temperature (i.e., 400 °C) deformation. The products of the deformation experiments will be characterized using various electron microscopy techniques, including electron backscatter diffraction (to quantify deformation microstructures and determine the deformation mechanisms that accommodated strain) and X-ray mapping (to determine compositional zoning that developed during experiments). The relationship among these features and U-Pb dates (evaluated using a combination of secondary ion mass spectrometry and atom probe tomography) will reveal how the development of deformation microstructures affects the U-Pb system in titanite. These integrated datasets will inform the best practices for dating crustal deformation with titanite in naturally deformed rocks, thereby providing a transformative advancement in Earth science research. The broader impacts of this work will focus on improving the diversity, equity, and inclusion of the Earth sciences through outreach activities with youth-facing organizations and by mentoring undergraduate students from underrepresented groups in research projects.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.