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

北方加州海岸山脉的折返作用，以及一般的造山带，是驱动隆升的地球动力学过程与响应隆升速率和模式的地表过程相互作用的结果。各种方法已被用来确定模式的剥露，但放置强大的，量化的限制，这些估计是困难的，因为反馈和大规模的地球动力学，热，景观evolutionprocess之间的联系。目前迫切需要一种技术来限制地壳浅层（低温）岩石的轨迹，以限制活动造山带的隆起和折返。最近，（U-Th）/He热年代学已被确定为一个潜在的工具，以帮助定量限制折返和隆升。（U-Th）/He系统的优点是封闭温度低（磷灰石为60-70 ℃），因此原则上它记录了最后几公里的去顶过程。作为一种低温热时计，使（U-Th）/He对地貌研究如此有吸引力的相同特性也提出了关于其在复杂的热历史和/或构造历史地区的效用的问题。目前还不确定这一工具是否能从一个复杂的信号中提取有意义的信息，该信号既包含了折返历史，也包含了由折返驱动的不可避免的热反馈。在本项目中，我们将应用（U-Th）/He定年技术，结合景观演化、热动力学和地球动力学模拟，来评估（U-Th）/He定年技术是否可以可靠地应用于热或地貌不稳定的活动构造地区。

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.