Metamorphic and Isotopic Studies of Mylonite

糜棱岩是由沿着断层磨碎的岩粉形成的。这些岩石已经得到了大量的研究，但由于它们细小的、几乎无法触及的颗粒尺寸，取得进展一直很困难。目前人们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，还因为老断层可能是变质和热液流体流动的深通道。建议的研究包括：(1)确定糜棱岩中达到化学和同位素平衡的区域的大小；(2)测量反应进程和化学交代作用以估计流体-岩石比；(3)采用Rb-Sr和U-Pb同位素方法测定糜棱岩化的年龄。这些方法将应用于佐治亚州布里瓦德断裂带、康涅狄格州希望谷剪切带和加利福尼亚州博雷加斯普林斯糜棱岩带的糜棱岩。对不同P-T流体环境中糜棱岩的详细研究进行比较，应该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.