Compaction of quartzite at low pressure using synchrotron X-ray diffraction multi-anvil apparatus

Abstract:

Multi-anvil deformation apparatus in the synchrotron have been used conventionally by mineral physicists to understand the rheology of deep earth materials. Instead of simulating such high pressure (in the order of tens of GPa) and temperature (up to thousands of degrees) conditions, this study pioneered to investigate systematically rock deformation at low pressure (in the order of hundreds of MPa) and room temperature (~25^oC) in this setting. We present new mechanical data on quartzite, as well as siltstone, under compaction. Stress and strain on individual quartz grains were resolved by analyzing the in-situ collection of X-ray beam diffracted by the rock matrix. With increasing pressures, the diffraction peaks were observed to be broadened, which has been widely observed in other compaction studies. More interestingly, peak shapes were evolved asymmetrically as pressure increased. Based on this evolution, stress distribution of quartz grain in these samples were evaluated quantitatively. Our study yielded comprehensive knowledge on mechanical behavior of quartzite and siltstone.