Collaborative Research: Experimental deformation of monazite and titanite: Implications for interpretation of petrochronologic data

合作研究：独居石和钛矿的实验变形：对岩石年代学数据解释的启示

• 批准号: 2217837
• 负责人: William Nachlas
• 金额: $ 3.48万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2217837&HistoricalAwards=false
• 关键词: Collaborative; Research; Experimental; deformation; monazite

The deformation behavior of rocks controls the strength of the lithosphere, the location and intensity of earthquakes, the response of Earth to impact events, and the concentration and deposition of ore minerals. To understand the conditions and duration under which rocks deformed in the geologic past, and to improve understanding of earthquake processes, mineral resource identification, and crustal strength modelling, we will conduct a series of experiments on minerals important for geologic age dating. These deformation experiments will be conducted at conditions which simulate environments deep within the Earth’s crust. The principal investigators will fabricate synthetic rock samples embedded with natural mineral grains and use a rock deformation apparatus to impose high stress and strain conditions typical of deep Earth shear zones. The experiments will focus on the deformation behavior of accessory phase minerals titanite and monazite, which are routinely used for petrochronology, a technique which uses radiometric age dating to determine the timing of ancient metamorphic reactions and deformation events. The deformation behavior of the major rock-forming minerals (e.g., quartz, feldspar, olivine) has been well-studied, but our experiments will be among the first to investigate the deformation behavior of accessory phase minerals. Accessory phase minerals, such as monazite, are reservoirs for Rare Earth Elements (REEs) and the results of our experiments will provide better understanding of REE mobilization within fault zones. Societal benefits of the project include direct training of graduate and undergraduate students and a postdoctoral researcher in experimental and analytical skills that are valuable in many high-level government, defense, and industrial laboratories. Outreach efforts will involve developing earth science curricula for Providence, RI elementary school. The Department of Earth, Environmental and Planetary Sciences at Brown has an active outreach program known as the Science-Teaching and Education Program (STEP), which partners with local teachers to develop earth science modules in their classes. The project will also contribute to the broadening of underrepresented groups in STEM. The goal of this project is to experimentally deform a selection of accessory phase minerals and use multiple advanced microanalytical techniques to examine how various deformation and recrystallization mechanisms affect the distribution of elements and isotopes important for geochronology. The researchers will conduct a multi-step experimental protocol consisting of deformation in a Griggs-rig solid medium deformation apparatus followed by high temperature static annealing of a subset of samples. Accessory phases monazite and titanite with well-characterized trace element contents will be embedded as porphyroclasts in a matrix of quartz, synthetic quartz, or feldspar and deformed under prescribed temperatures, pressures, and strain rate conditions. Multiple advanced analytical techniques will allow us to investigate the composition and structure of deformed samples from the aggregate to atomic scale. The principal investigators will quantify the influence of lattice defects on the mobility of impurity elements and consequences of recrystallization for interpreting the geochemistry of deformed minerals. Our results will provide fundamental constraints on the rheological behavior of accessory phase minerals and enable more confident applications of accessory phase geochronology and geothermometry to deformed rocks.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.

岩石的变形行为控制着岩石圈的强度，地震的位置和强度，地球对影响事件的反应以及矿石矿物质的浓度和沉积。为了了解岩石在地质过去变形的条件和持续时间，并提高对地震过程，矿产资源识别和地壳强度建模的理解，我们将对矿物进行一系列实验，对地质年龄约会很重要。这些变形实验将在模拟地壳深处的环境下进行。主要研究人员将制造嵌入天然矿物晶粒的合成岩石样品，并使用岩石变形设备施加高应力和高应变条件的深层剪切区。实验将集中于辅助相矿物质钛和独居石的变形行为，这些矿物质通常用于石油年代学，该技术使用辐射年龄约会来确定古代变质反应和变形事件的时间。主要研究了主要的岩石形成矿物（例如石英，长石，橄榄石）的变形行为，但我们的实验将成为第一个研究辅助相矿物质变形行为的人之一。辅助相矿物质（例如独居石）是稀土元素（REE）的储层，我们的实验结果将更好地理解故障区域内的REE动员。该项目的社会益处包括对研究生和本科生的直接培训以及实验和分析技能的博士后研究员，这些研究人员在许多高级政府，国防和工业实验室中都很有价值。外展工作将涉及为RI小学的普罗维登斯开发地球科学课程。布朗的地球，环境和行星科学系有一个活跃的外展计划，称为科学教学和教育计划（Step），该计划与当地教师合作，在其课程中开发地球科学模块。该项目还将有助于扩大STEM中代表性不足的群体。该项目的目的是实验变形辅助相矿物质的选择，并使用多种先进的微分析技术来检查各种变形和重结晶机制如何影响元素和同位素的分布对地质学重要。研究人员将进行多步实验方案，该方案包括在Griggs-rig固体培养基变形设备中的变形，然后进行样品子集的高温静态退火。带有良好特征的微量元素含量的辅助阶段和钛将嵌入在石英，合成石英或长石的基质中，并在规定的温度，压力，压力和应变速率条件下变形。多种高级分析技术将使我们能够研究从骨料到原子量表的变形样品的组成和结构。首席研究人员将量化晶格缺陷对杂质元素的迁移率的影响以及重结晶对解释变形矿物质的地球化学的影响。我们的结果将对辅助阶段矿物的流变行为提供基本限制，并使附属阶段地球文量学和地理测量学对变形岩石的应用更加自信。该奖项反映了NSF的法定任务，并被认为是通过基金会的智力优点和更广泛的影响审查的审查标准来通过评估来通过评估来获得的支持。