Petrofabric studies of some fine-grained rocks by means of x-ray diffraction

[摘要] Crystallographic orientation in rocks too, fine-grained to be studied optically can be determined by X-raydiffraction. Absorption and geometric corrections are unnecessary because, by studying hemispherical surfaces, absorption is held constant. Poughquag quartzite, Star Mountain rhyolites, basalt and mylonites were studld. All quartz crystals in the examined samples are parallel to c-axes. The preferred orientations parallelto c-axes or a-axes of feldspar (orthoclase or labradorite), microlites are more common than those perpendicular to c-axes or a-axes of feldspar (orthoclase of labradorite) crystalsin extrusive igneous and highly deformed metamorphic rocks. In deducing the flow direction from the fabric diagrams of rhyolitic or basaltic rocks, the preferential orientation has been supposed to be parallel with the lava flow, while incase of highly deformed mylonitic rocks the preferred orientation was considered to be parallel to the movement direction.

[发布机构] Rice University