Direct measurement of the quartz c-axis using neutron diffraction

Quartz c-axis pole figures are widely used across structural geology and geophysics to gain insights into crustal properties, yet their direct measurement using bulk diffraction techniques has hitherto been unsuccessful. In this contribution, we present measurements of the quartz c-axis using neutron diffraction. This has been achieved by combining advances in neutron diffraction instrumentation, high neutron fluxes and fast data acquisition, with carefully performed diffraction pattern analysis to resolve low intensity diffractions on the (003) diffraction peak hidden in the shoulder of the higher intensity (112) peak. These measurements have allowed us to assess 'recalculated' c-axis pole figures (i.e. those predicted from ODF functions) against measured c-axis pole figures, and thus assess the reliability of quartz c-axis pole figures past and present. We find that measured and recalculated pole figures are generally in good agreement in both strongly and weakly textured rocks, and that inclusion of the (003) pole figure into quartz texture analysis routines improves ODF construction.