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

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该项目调查了在自然界和实验中，在广泛的温度和变形条件下，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重结晶对石英中Ti迁移的影响，探讨了Ti在变形石英中的迁移规律。同时，本研究利用天然石英岩研究了两种构造环境：（1）收缩（逆冲）系统，其中岩石在加热和埋藏过程中变形;石英显微结构在狭窄的温度范围内锁定，但显示出广泛的显微结构;（2）伸展性（拆离）系统，其中岩石在很宽的温度范围内变形，但随着热岩向地球表面挖掘，形成了类似的微观结构。在拆离和逆冲系统的实验和天然岩石中，该项目研究了继承的Ti如何作为变形和温度条件的函数重新分布。天然样品来自澳大利亚中部（逆冲断层）Ruby Gap Duplex的Heavitree石英岩;瑞士阿尔卑斯山西部的Siviez-Mischabel推覆体（逆冲断层）;以及美国西部的Kettle和Snake Range伸展拆离系统。研究方法包括：石英微结构的岩相学和电子背散射衍射表征、再结晶类型和晶体学择优取向;石英中微量元素分区的阴极发光成像;实验和天然样品中石英中钛的离子探针分析。石英是二氧化硅（SiO2），但可能含有微量的其他元素，如钛和铝。这些微量元素的丰度可能与温度相关，从而提供了一种方法来计算含石英岩石在构造事件期间形成时锁定其成分的温度。记录地壳在不同构造环境（收缩、伸展）下的热演化，对于了解构造过程如何随时间推移而运作十分重要。虽然石英的Ti含量越来越多地被用来计算富石英岩石的古温度，但变形在石英中微量元素分布中的作用必须加以理解。通过野外和实验相结合的方法研究不同热环境和构造背景下的变形效应，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.