SGER: Testing the Viability of (U-Th)/He Thermochronology in Complex Tectonic Systems

北加州海岸山脉的挖掘，以及造山带的挖掘，通常是由驱动隆升的地球动力学过程和响应隆升速率和模式的地表过程的相互作用造成的。各种各样的方法被用来确定挖掘模式，但由于大尺度地球动力学、热和景观演化过程之间的反馈和联系，对这些估计进行可靠的、可量化的约束是困难的。为了抑制活动造山带的隆升和掘出，迫切需要一种技术来约束地壳浅层（低温）岩层的运动轨迹。最近，(U-Th)/He热时计被认为是一种潜在的工具，有助于定量地限制挖掘和隆升。（U-Th）/He系统的优点是封闭温度低（对于磷灰石来说~ 60-70℃），因此基本上可以记录最后几公里的拆顶过程。作为一种低温度时计，(U-Th)/He在地貌学研究中如此有吸引力的相同特征也提出了它在复杂的热和/或构造历史地区的实用性问题。目前尚不确定该工具能否从复杂的信号中提取有意义的信息，这些信号包括挖掘历史和由挖掘驱动的不可避免的热反馈。在这个项目中，我们将应用(U-Th)/热热测年技术，结合景观演化、热模拟和地球动力学模拟，来评估(U-Th)/He测年是否可以自信地应用于非热稳态或地貌稳态的活动构造活动区域。

Exhumation in the northern California Coast Ranges, and orogens in general, results fromthe interplay of geodynamic processes that drive uplift and surface processes that respond to therates and patterns of uplift. A variety of approaches have been used to determine patterns ofexhumation, but placing robust, quantifiable constraints on these estimates is difficult because ofthe feedbacks and linkages among large scale geodynamic, thermal, and landscape evolutionprocesses. There is a critical need for a technique to constrain the trajectory of rocks at shallow-crustal (low-temperature) levels to constrain uplift and exhumation in active orogenic belts. Mostrecently, (U-Th)/He thermochronometry has been identified as a potential tool to helpquantitatively constrain exhumation and uplift. The (U-Th)/He system has the advantage of a lowclosure temperature (~ 60-70 C for apatite) and thus in principal it records the last fewkilometers of unroofing. As a low-T thermochronometer the same characteristics that make (U-Th)/He so appealing for geomorphic studies also raise questions about its utility in regions ofcomplex thermal and/or tectonic histories. It is uncertain whether this tool can extract meaningfulinformation from a complex signal that incorporates both the exhumation history and theinevitable thermal feedbacks driven by that exhumation. In this project we will apply (U-Th)/Hethermochronometry coupled with landscape evolution, thermal and geodynamic modeling, toevaluate if (U-Th)/He dating can be confidently applied in regions of active tectonism that are notin thermal or geomorphic steady-state.