Field-based Analysis of Diapiric and Channel Flow of Partially Molten Crust

造山过程（造山作用）的特征是地壳增厚、大量的部分熔融和大陆高原的形成。地球动力学模型表明，部分熔融的地壳通过在水道中横向流动或在底辟中垂直流动来重新分配造山带中的物质和热量。尽管沟道流和底辟流是控制造山带演化的一级机制，但这些模式的野外检验却相对滞后。该项目的重点是对两个挖掘出来的混合岩地形进行地质研究，即Okanogan-Kettle穹丘（北美科迪勒拉山脉）和Naxos穹丘（爱琴海变质核杂岩）。在这些地形中，混合岩结构和织物保存了通道/底辟流的记忆和部分熔融地壳与上地壳相互作用的程度之前和期间的通道和圆顶的折返。该项目的方法包括利用野外测绘和磁化率各向异性分析来确定混合岩中流动的几何形状和运动学。变质组合的温压和结构分析重建了混合岩的压力和温度历史，这是不同的通道和底辟流。地质年代学分析，使用原位测年（SHRIMP facilty）的锆石颗粒结晶在已知的关系到变形的浅色体，日期的流动部分熔融地壳。此外，已知关系的变质组合独居石的定年提供了时间上的压力-温度path. The冷却这些岩石的时间，接近氩和裂变径迹地质年代学方法，评估通道/底辟流和折返的成因关系。这种综合方法适用于两个第三纪造山段的部分熔融地壳造山作用和地壳流动和板块地球动力学之间的关系进行评估。

Mountain building processes (orogenesis) are characterized by crustal thickening, abundant partial melting, and the formation of continental plateaus. Geodynamic models show that partially molten crust redistributes mass and heat in the orogen by flowing laterally in a channel or vertically in diapirs. Although channel flow and diapiric flow are first-order mechanisms controlling the evolution of orogens, field-testing of these models is lagging. This project is concentrating on geologic studies of two exhumed migmatite terrains, the Okanogan-Kettle dome (North American Cordillera), and the Naxos dome (Aegean metamorphic core complex). In these terrains, migmatite structures and fabrics have preserved the memory of channel/diapiric flow and the extent to which the partially molten crust interacts with the upper crust prior to and during exhumation of the channel and the domes. The project's methodology includes the determination of the geometry and kinematics of flow in migmatites using both field mapping and the analysis of anisotropy of magnetic susceptibility. Thermobarometric and textural analyses of metamorphic assemblages reconstructs the pressure and temperature histories of migmatites, which are distinct for channel and diapiric flow. Geochronologic analyses, using in-situ dating (SHRIMP facilty) of zircon grains crystallized in leucosomes of known relationship to deformation, date the flow of partially molten crust. In addition, dating of monazite of known relationship to metamorphic assemblages offers temporal constraints on the pressure-temperature path. The timing of cooling of these rocks, approached by argon and fission-track geochronologic methods, evaluates the genetic relationship between channel/diapiric flow and exhumation. This integrated methodology applied to two Tertiary orogenic segments evaluates the role of the partially molten crust during orogeny and the relationship between crustal flow and plate geodynamics.