Metamorphic and Isotopic Studies of Mylonite

糜棱岩是由沿断层磨碎的岩石粉形成的。人们对这些岩石进行了大量的研究，但由于其细小的、几乎看不见的颗粒大小，研究进展一直很困难。目前对糜棱岩有相当大的兴趣，不仅因为它们可以提供有关地震机制的信息，而且因为古老的断层可以作为变质流体和热液流动的深层管道。拟进行的研究包括：(1)确定糜棱岩中实现化学和同位素平衡的结构域的大小；(2)测定反应过程和化学交代作用，估算流岩比；(3)采用Rb-Sr和U-Pb同位素测定糜棱岩化年代。这些方法将应用于佐治亚州布里沃德断裂带、康涅狄格州希望谷剪切带和加利福尼亚州博尔雷加斯普林斯糜棱岩带的糜棱岩。通过对不同P-T流体环境中糜棱岩的详细研究对比，可以分离出控制糜棱岩发育的重要因素。

Mylonites form from rock flour ground up along faults. The rocks have received a good deal of study but progress has been difficult because of their fine, almost impalpable grain size. There is considerable current interest in mylonites not only because they may yield information on earthquake mechanisms but also because old faults may act as deep conduits for the flow of metamorphic and hydrothermal fluids. The proposed research includes: (1) determination of the sizes of domains over which chemical and isotopic equilibrium is achieved in mylonites; (2) measurement of reaction progress and chemical metasomatism to estimate fluid-rock ratios; and (3) adapting Rb-Sr and U-Pb isotopic methods to dating mylonitization. These methodologies will be applied to mylonites from the Brevard fault zone, Georgia, the Hope Valley sheartone, Connecticut, and the Borrega Springs mylonite zone, California. The comparison of detailed studies of mylonites from a variety of P-T fluid environments should make it possible to isolate important factors controlling the development of mylonites.