The importance of clay mineral reactions on the seismic behavior of the San Andreas Fault: Part 2-Hydration states and timing of mineralization

在美国加利福尼亚州帕克菲尔德钻探的圣安德烈亚斯断层深度观测站（SAFOD）主孔提供了一个独特的机会，可以研究从活动断层系统深处收集的富含粘土的样品的性质，并评估它们对控制发震和蠕动行为的贡献。2005年，从岩心中收集了新鲜的岩屑，并在现场使用低粘度聚合物基树脂进行浸渍。在第一年的研究中，使用高分辨率显微镜和x射线衍射法对样品进行了表征。在第二年，层间水化状态将与原始粘土矿物结构一起确定。定量地表和层间约3 km深度处的吸附水量对于理解膨胀粘土在断裂过程中的作用至关重要。此外，利用关键断平面上与断裂相关的新晶伊利石矿物的40Ar/39Ar定年，将约束该断裂系统的成矿时间。这项研究将包括收集和研究新的样品材料，这些材料将在预定的2007年现场取心活动中可用。

The San Andreas Fault Observatory at Depth (SAFOD) main hole, drilled in Parkfield, California, USA, provides a unique opportunity to study the nature of clay-rich samples collected at depth from an active fault System and to assess their contribution to controlling seismogenic and creeping behavior. During 2005, fresh rock chips were collected from a core and impregnated onsite using low viscosity polymer-based resins. In the first year of research, samples were characterized using high resolution microscopy and X-ray diffractometry. In the second year, the interlayer hydration state will be determined along with the original clay mineral textures. Quantifying the amount of water adsorbed on surface and interlayer sites at circa 3 km depth is critical for understanding the role of swelling clays in the faulting process. Additionally, 40Ar/39Ar dating of fault-related neocrystallized illitic minerals on key fault planes will be used to constrain the timing of mineralization in this fault System. The study will include collection and study of new sample material that will become available during the scheduled 2007 site coring activities.