Water loss during dynamic recrystallization of Moine thrust quartzites, northwest Scotland
Water loss during dynamic recrystallization of Moine thrust quartzites, northwest Scotland
复制标题
苏格兰西北部莫因逆冲石英岩动态重结晶过程中的失水
DOI：
10.1130/g47041.1
复制
发表时间：
2020
期刊：
影响因子：
5.8
通讯作者：
Jay B. Thomas
中科院分区：
文献类型：
--
作者：
A. Kronenberg;K. Ashley;M. K. Francsis;C. Holyoke;Lynna P. Jezek;J. A. Kronenberg;R. Law;Jay B. Thomas
剪切寒武纪石英岩的分子水的红外吸收测量的下盘莫因逆冲揭示了减少水含量从4080至1570 ppm，增加重结晶跟踪到上覆的逆冲堆格伦库尔在苏格兰西北部。这些结果是相反的预期剪切应变和水含量之间的相关性变形的位错蠕变和水弱化过程中的石英。观察到的反相关性表明，流体包裹体和含水缺陷的晶粒内丢失的移动的晶界清扫和晶界扩散。虽然减少水含量可能会导致硬化化学弱化减少，石英糜棱岩在直接下盘（5毫米）的推力的特点是强烈的应变局部化，并含有最少的水，几乎没有证据表明剪切带加宽。水弱化似乎一直是重要的整个石英糜棱岩，控制水的存在，而不是水的浓度。残余夹杂物和晶界处的流体可能控制了水弱化的高水逸度。
Infrared absorption measurements of molecular water in sheared Cambrian quartzites in the footwall to the Moine thrust reveal a decrease in water content from 4080 to 1570 ppm with increasing recrystallization traced toward the overlying thrust at the Stack of Glencoul in northwest Scotland. These results are contrary to the expected correlation between shear strain and water content for quartz deformed by dislocation creep and water-weakening processes. The observed inverse correlation indicates that fluid inclusions and hydrous defects within grains were lost by mobile grain boundary sweeping and grain boundary diffusion. Although reduced water contents might lead to hardening as chemical weakening is diminished, quartz mylonites in the immediate footwall (5 mm) to the thrust are characterized by intense strain localization and contain the least water, and there is little evidence of shear zone widening. Water weakening appears to have been important throughout the quartz mylonites, controlled by the presence of water, not by water concentration. Fluids present within relict inclusions and at grain boundaries may have governed the high water fugacities critical for water weakening.