Rheology and microstructural evolution of serpentine

蛇纹石是一组含水矿物，通常形成于地球上的沿着断层和其他界面，在那里水能够与其他无水矿物反应。由于蛇纹岩具有许多不寻常的物理性质，因此推测蛇纹岩族矿物在构造板块之间的边界动力学中起着重要作用。此外，蛇纹岩还可以控制地震发生或不发生的地点。 然而，蛇纹岩只在很窄的压力和温度范围内是稳定的，这阻碍了实验研究其行为。这项研究将涉及两组新的实验，以阐明如何蛇形变化的形状或结构时，地球一样的变形条件下应用。更广泛的影响包括培训一名研究生，在可视化实验室开发教育和推广模块，以及跨学科的科学影响。该项目的目标是进一步阐明叶蛇纹石的流变学和相关变形显微结构，蛇纹石的高压和高温相。提出了两组实验。第一组实验将使用圣路易斯华盛顿大学的大体积扭转（LVT）装置，研究多晶蛇纹石作为应变函数的微观结构演变。这些实验的目的是表征由变形产生的晶体学优选取向（CPO），并确定产生稳态微观结构的条件。将获得的数据上的叶蛇纹石CPO的瞬态演化需要解释地震波的速度和地震各向异性的地区，推断是本。第二组实验将使用微机械方法，包括纳米压痕和微柱压缩测试，以精确测量叶蛇纹石高达600摄氏度的塑性流变学。这些数据将被用来约束流律叶蛇纹石在有关俯冲带的条件下，并可能被用于在未来的努力，以模拟在板interfaces.This奖项的变形反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Serpentine is a group of hydrous minerals that is commonly formed along faults and other interfaces in Earth where water is able to react with other anhydrous minerals. Because serpentine has a number of unusual physical properties, it is hypothesized that serpentine-group minerals play an essential role in the dynamics of boundaries between tectonic plates. Furthermore, serpentine may control where earthquakes can or cannot occur. However, serpentine is only stable through a narrow range of pressure and temperature conditions, which has hindered experimental efforts to unravel its behavior. This study will involve two sets of novel experiments to elucidate how serpentine changes shape or structure when Earth-like deformation conditions are applied. Broader Impacts include training of a graduate student, development of educational and outreach modules in a visualization laboratory, and cross-disciplinary science impact.The objective of this project is to clarify further the rheology and associated deformation microstructures of antigorite, the high pressure and temperature phase of serpentine. Two sets of experiments are proposed. The first set of experiments will investigate microstructural evolution of polycrystalline serpentine as a function of strain, using the Large Volume Torsion (LVT) apparatus at Washington University in St. Louis. The purpose of these experiments is to characterize the crystallographic preferred orientation (CPO) generated by deformation and determine the conditions at which steady-state microstructures are produced. The data that will be obtained on the transient evolution of antigorite CPO are needed to interpret seismic wave-speeds and seismic anisotropy in regions where serpentine is inferred to be present. The second set of experiments will use micromechanical methods, including nanoindentation and micropillar compression testing, to measure precisely the plastic rheology of antigorite up to 600 degrees C. These data will be used to constrain flow-laws for antigorite at conditions relevant to subduction zones, and may be used in future efforts to model deformation at the slab interface.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.