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: 1725170
• 负责人: Basil Tikoff
• 金额: $ 10.73万
• 依托单位: University of Wisconsin-Madison
• 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=1725170&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.

当地壳由于构造板块的碰撞而收缩时，山脉就形成了。这种收缩在地壳中产生花岗岩岩体，并通过剪切带（剧烈变形的局部区域）使这些花岗岩岩体变形。这两个过程都在花岗岩上留下了“织物”的痕迹，这是记录岩石变形的矿物排列。钛矿矿物在地壳花岗岩形成过程中和岩石结构形成过程中结晶，这两个事件都可以利用钛矿晶体中铀放射性衰变成铅来测定年代。 这种测定剪切带的新方法将用于检查造山过程和岩石结构的发育，随后可以控制进一步的岩浆侵位、断层、流体流动和金属矿石矿化。本研究将重点关注钛矿矿物在变形过程中的物理和化学变化。构造地质学技术将通过岩石的露头和微观结构研究物理变化，电子显微镜将量化单个矿物颗粒的再结晶。将通过 X 射线和质谱技术测量钛矿的化学变化，并通过测量铀-铅同位素比来测定单个晶体的年代。这些技术将应用于爱达荷州西部和加利福尼亚州中东部剪切带的两个研究区域。这些地区的岩石显示出广泛的结构发育，从不变形到普遍剪切。通过上述方法测量的各种变形程度将用于测试岩石织物的强度在剪切带运动过程中如何发展。这两个研究领域的成果将包括建立亚百万年分辨率的变形时间、剪切带内应变积累的时空模式以及岩浆作用和变形之间的反馈的方法。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理信息学数据库开发。这项研究的结果将通过同行评审期刊、专业会议、数据存储库和网站广泛传播。