Collaborative Research: The role of Grain Boundary Migration in Water Weakening of Naturally Deformed Quartz

合作研究：晶界迁移在自然变形石英水弱化中的作用

• 批准号: 2120302
• 负责人: Sven Morgan
• 金额: $ 43.33万
• 依托单位: Regents of the University of Michigan - Dearborn
• 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: 2021-08-15 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2120302&HistoricalAwards=false
• 关键词: Collaborative; Research; role; Grain; Boundary

This research is designed to understand how sub-microscopic amounts of water, in minerals, can affect their strength. The overall effect of this tiny amount of water, in rocks, can have a big significance to how plates interact. For example, the Indian plate is colliding with the Asian plate to produce the Himalayas, but the strong Indian plate is not deforming while the weaker Asian plate is folding, faulting, experiencing earthquakes, and rising to produce the tallest mountains on Earth. The uplift of the Tibetan Plateau (which is five times the area of France) to an elevation of over 3 miles high (4.8 km) is remarkable. One possibility for this huge difference in plate strength is that deep rocks of the Indian plate are “dry” (no sub-microscopic water) whereas deep rocks of the Asian plate are “wet” (they contain some sub-microscopic water). Therefore, it is important to understand how and when this tiny amount of water gets into the rocks. This research project involves collecting rocks, in the mountains of California, along a 5 km transect where it is already known that rocks undergo the transition from strong to weak behavior. Detailed chemical analyses with advanced micro-imaging techniques will be conducted to determine exactly how and where along the transect the water gets into and out of the effected minerals. This research will support the education of one post-doctoral researcher, 4-6 undergraduate researchers, as well as 12 inner city Detroit High School (César Chávez Academy High School) students and three High School teachers who will travel to California with the research team to sample and learn about how water affects mountain building and plate tectonics. The effects of water on shaping this part of Earth are visually evident (previous glaciers, pre-historic and historic lake beds) and the effects of climate change, drought and fires, and human intervention (water piped to Los Angeles) will also be examined. The goal of this project is to determine if grain boundary migration allows water to enter the quartz crystal lattice and cause weakening. Oxygen isotope data will be used as the main proxy for tracking water infiltration. Harkless Formation quartzite samples will be collected along a 5 km transect, oriented perpendicular to the contact with the Eureka Valley-Joshua Flat-Beer Creek pluton in the White-Inyo Range of California. Contact metamorphism is first observed at 2.9 km from the pluton and concordancy occurs abruptly at 1.1 km where the Harkless folds 90° and is intensely attenuated. This abrupt transition is assumed to be a “rolling hinge”, that progressed outward as the pluton expanded during emplacement. Samples will be collected across this transition between regional structures and the forceful concordance of country rocks with the intrusion. Standard petrography and scanning electron microscopy techniques with advanced analysis including electron backscatter diffraction and cathodoluminescence, will be used to document; 1) where exactly grain boundary migration begins, where it becomes pervasive and, 2) where the crystallographic preferred orientation begins to develop and how it develops across the transition. Using a focused Secondary Ion Mass Spectrometer beam with a small spot size (6-10µm pit size), grain boundaries will be analyzed between unmigrated and migrated parts of the grains to determine the oxygen isotope signatures for tracking water infiltration and delineating the potential sources of this water. Fourier-transform infrared spectroscopy will also be used to document the overall concentrations of water (OH) on a microscopic scale in associated minerals. Trace element data will be input into several TitaniQ models to determine the temperatures during deformation and the overall Ti diffusional partial re-equilibration during the cooling history. This overall strategy will help correlate rock/mineral strength and deformation behavior with sub-microscopic water phenomena in minerals from intense heating and pressure during mountain building processes.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.

这项研究旨在了解矿物中亚微观量的水如何影响其强度。 岩石中微量的水的整体效应对板块如何相互作用具有重大意义。 例如，印度板块与亚洲板块碰撞产生了喜马拉雅山，但强大的印度板块没有变形，而较弱的亚洲板块正在折叠，断层，经历地震，并上升，产生地球上最高的山脉。青藏高原（面积是法国的五倍）上升到海拔超过3英里（4.8公里）是非常显著的。 板块强度的巨大差异的一种可能性是印度板块的深层岩石是“干的”（没有亚微观水），而亚洲板块的深层岩石是“湿的”（它们含有一些亚微观水）。 因此，重要的是要了解这些微量的水是如何以及何时进入岩石的。 该研究项目涉及收集岩石，在加州的山区，沿着5公里的横断面，它已经知道，岩石经历从强到弱的行为的转变。 将利用先进的显微成像技术进行详细的化学分析，以确定水如何以及在沿着断面的何处进入和流出受影响的矿物。 这项研究将支持一名博士后研究人员，4-6名本科研究人员，以及12名内城底特律高中（塞萨尔查韦斯学院高中）的学生和三名高中教师的教育，他们将与研究团队一起前往加州，以采样和了解水如何影响造山运动和板块构造。 水对塑造地球这一部分的影响在视觉上是显而易见的（以前的冰川，史前和历史湖床），气候变化，干旱和火灾以及人类干预的影响（水管到洛杉矶）也将被检查。 这个项目的目标是确定晶界迁移是否允许水进入石英晶格并导致弱化。 氧同位素数据将被用作跟踪水渗透的主要代用指标。 将沿着5 km横断面采集Harkless地层石英岩样品，该横断面垂直于与加州怀特-因约山脉中的尤里卡山谷-约书亚弗拉特-比尔溪岩体的接触面。 接触变质作用在距岩体2.9km处最先出现，整合作用在距岩体1.1km处突然发生，Harkless褶皱呈90°，并强烈衰减。 这种突然的过渡被认为是一个“滚动枢纽”，在侵位过程中随着岩体的膨胀而向外发展。 将在区域结构和围岩与侵入体的强烈一致性之间的过渡区收集样本。 标准岩相学和扫描电子显微镜技术与先进的分析，包括电子背散射衍射和阴极射线发光，将用于文件; 1）确切的晶界迁移开始，它变得无处不在，2）晶体学的优先方向开始发展，以及它如何发展跨越过渡。使用具有小斑点尺寸（6-10µm凹坑尺寸）的聚焦二次离子质谱仪光束，将分析颗粒的未迁移和迁移部分之间的颗粒边界，以确定氧同位素特征，用于跟踪水渗透和描绘这种水的潜在来源。 傅里叶变换红外光谱也将用于记录水（OH）的总体浓度在微观尺度上在相关的矿物。将微量元素数据输入到几个TitaniQ模型中，以确定变形期间的温度和冷却历史期间的整体Ti扩散部分再平衡。 这一整体战略将有助于关联岩石/矿物强度和变形行为与矿物中的亚微观水现象，从强烈的加热和压力在造山过程中。这一奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。