Collaborative Research: Using Titanite as a Petrochronometer for Direct Fabric Dating of High Temperature Systems

合作研究：使用钛矿作为石油天文台计直接测定高温系统的织物年代

• 批准号: 1725229
• 负责人: Mark Schmitz
• 金额: $ 22.72万
• 依托单位: Boise State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-01 至 2021-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1725229&HistoricalAwards=false
• 关键词: Collaborative; Research; Using; Titanite; Petrochronometer

Mountain ranges form when the Earth's crust contracts due to the collision of tectonic plates. This contraction generates granite plutons in the crust and deforms those granite plutons through shear zones (localized regions of intense deformation). Both processes imprint a "fabric" on the granite, an arrangement of minerals that records the deformation of the rock. The mineral titanite crystallizes during the formation of granite in the crust and during the formation of rock fabric, and both events can be dated using the radioactive decay of uranium into lead within titanite crystals. This new method for dating shear zones will be used to examine mountain building processes and the development of rock fabrics that subsequently can control further magma emplacement, faulting, fluid flow, and metal ore mineralization. This study will focus on the physical and chemical changes in the mineral titanite during deformation. Structural geology techniques will investigate the physical changes through the outcrop and microscale structures of the rock, and electron microscopy will quantify the recrystallization of individual mineral grains. Chemical changes in titanite will be measured by X-ray and mass spectrometry techniques, and individual crystals will be dated using measurements of uranium-lead isotope ratios. These techniques will be applied in two study areas, in shear zones in western Idaho and east-central California. Rocks from these areas show a wide range of fabric development, from non-deformed to pervasively sheared. The variety of degrees of deformation measured through the methods described above will be used to test how the intensity of a rock fabric develops during shear zone movement. Outcomes in both study areas will include methodologies to establish sub-million year resolution of the timing of deformation, the spatial-temporal pattern of strain accumulation within shear zones, and the feedbacks between magmatism and deformation. This project will more broadly support graduate research training, on-line science learning modules, and geoinformatics database development. Results of this research will be widely disseminated through peer-reviewed journals, professional meetings, data repositories, and websites.

由于构造板的碰撞，地球的地壳合同时，山脉形成。这种收缩在地壳中产生花岗岩岩石，并通过剪切区（局部变形区域）变形那些花岗岩岩石。这两个过程都在花岗岩上贴上“织物”，这是记录岩石变形的矿物质的布置。矿石在地壳中和岩石织物形成过程中形成花岗岩期间的矿物质钛铁矿可以使用铀的放射性衰减到钛铁矿晶体内的铅。 这种用于剪切区的新方法将用于检查山地建筑工艺和岩石织物的发展，后来可以控制进一步的岩浆，断层，流体流动和金属矿石矿化。这项研究将集中于变形过程中矿物钛矿的物理和化学变化。结构地质技术将通过岩石的露头和显微镜结构研究物理变化，电子显微镜将量化单个矿物晶粒的重结晶。钛铁矿的化学变化将通过X射线和质谱技术来测量，并使用铀潜在同位素比的测量来确定单个晶体的日期。这些技术将在爱达荷州西部和东部加利福尼亚州西部的剪力区域中应用于两个研究领域。这些区域的岩石显示出广泛的织物发育，从不形成到泛滥的剪切。通过上述方法测量的各种变形程度将用于测试在剪切区运动过程中岩石织物的强度如何发展。这两个研究领域的结果都将包括建立变形时机的低于以下的方法，剪切区域内应变积累的时空模式以及岩浆和变形之间的反馈。该项目将更广泛地支持研究生研究培训，在线科学学习模块和地球信息学数据库开发。这项研究的结果将通过同行评审的期刊，专业会议，数据存储库和网站广泛传播。