Collaborative Research: Titanium in Deforming Quartz and the Thermo-mechanics of Detachment and Thrust Systems

该奖项由2009年美国复苏和再投资法案(公法111-5)资助。该项目在自然界和实验的广泛温度和变形条件下调查变形对钛(Ti)和其他微量元素在石英中分布的作用。通过高压/高温实验研究了动态再结晶对钛在石英中迁移的影响，探讨了钛在变形石英中的迁移性。与此同时，这项研究使用天然石英岩来研究两种构造环境：(1)收缩(逆冲)系统，其中岩石在加热和埋藏过程中变形；石英微结构锁定在较小的温度范围内，但显示出广泛的微结构；(2)伸展(拆离)系统，其中岩石在较宽的温度范围内变形，但在热岩向地球表面折返时发展出类似的微结构。在实验和来自滑脱和逆冲系统的天然岩石中，这个项目研究了继承的钛是如何随着变形和温度条件的变化而重新分布的。天然样品来自澳大利亚中部Ruby Gap Duplex中的Heavitree石英岩(逆冲)；瑞士西部阿尔卑斯山的Siviez-Mischabel推覆(逆冲)；以及美国西部的Kettle和Snake山脉伸展拆离系统。研究方法包括岩相学和电子背散射衍射表征石英的微观结构、重结晶类型和晶体择优取向；阴极发光成像研究石英中的微量元素分带；以及离子探针分析实验和自然样品中的石英中的钛。石英是二氧化硅(SiO_2)，但可能含有微量其他元素，如钛和铝。这些微量元素的丰度可能与温度相关，从而提供了一种计算含石英岩石在构造事件期间形成时其成分锁定的温度的方法。记录地壳在不同构造环境(收缩、伸展)下的热演化对于理解构造过程如何随着时间的推移而运作很重要。虽然石英中的钛含量越来越多地被用来计算富石英岩石的古温度，但必须了解变形在石英中微量元素分布中的作用。结合野外和实验研究不同热环境和构造环境下变形的影响，可以评价变形对石英中微量元素分布的影响。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).The project investigates the role of deformation in the distribution of titanium (Ti) and other trace elements in quartz over a wide range of temperature and deformation conditions in nature and experiments. The mobility of Ti in deforming quartz is addressed by high-pressure/high-temperature experiments that test the role of dynamic recrystallization on Ti migration in quartz. In parallel, this research uses natural quartz rocks to investigate two tectonic settings: (1) contractional (thrust) systems, in which rocks deformed during heating and burial; quartz microstructures locked in over a narrow range of temperatures but display a wide range of microstructures; and (2) extensional (detachment) systems, in which rocks deformed over a wide temperature range but developed similar microstructures as hot rocks exhumed towards the Earth's surface. In experiments and natural rocks from detachment and thrust systems, this project examines how inherited Ti is redistributed as a function of deformation and temperature conditions. Natural samples are from the Heavitree Quartzite in the Ruby Gap Duplex, central Australia (thrust); the Siviez-Mischabel nappe in the western Alps, Switzerland (thrust); and the Kettle and Snake Range extensional detachment systems, western United States. Research methods include petrographic and electron backscatter diffraction characterization of quartz microstructure, types of recrystallization, and crystallographic preferred orientation; cathodoluminescence imaging of trace element zoning in quartz; and ion microprobe analysis of Ti in quartz in experimental and natural samples.Quartz is silicon dioxide (SiO2) but may contain trace amounts of other elements, such as titanium and aluminum. The abundance of these trace elements may correlate with temperature, thereby providing a means to calculate the temperature at which quartz-bearing rocks locked in their composition when they formed during tectonic events. Documenting the thermal evolution of the crust in different tectonic settings (contraction, extension) is important for understanding how tectonic processes operate over time. Although the Ti content of quartz is increasingly used to calculate paleo-temperatures of quartz-rich rocks, the role of deformation in the distribution of trace elements in quartz must be understood. A combined field and experimental study of the effect of deformation in different thermal and tectonic settings can evaluate the effect of deformation on trace element distribution in quartz.