Neutron Scattering

dependent pole densities, and (4) graphical representation of the pole densities in stereographic
projection using a normalized grid in multiples of random distribution. The
experimental pole figures are shown in Fig . 18.26.
Pole figure inversion and ODF calculations bas been performed using the program
MENTEX [8] . Experimental and calculated pole figures of some hkl are presented in Fig .
18 .27 . The (001) pole figure is of special importance for the quartz structure, because (001)
informs on the orientation distribution ofthe optically relevant hexagonal [001] axes and thus
permts a comparison to an individual grain analysis at an U-stage (sec Fig . 18 .15) . While the
optical data are confmed to this [001] direction, the neutron data permit an overall description
of the quartz texture by additional information on preferred orientation of other quartzrelevant
planes and foiras like prisms and rhombs . The inteipretation of the quartz texture is
given in the typical nomenclature of a geologist (compare Fig . 18 .27) :
Fig . 18.27 : Observed and calculated
neutron polefigures (X, Y.-
see text) .
Top roiv :
experimentalpolefigures {m},
{r+z} and {a} (see text) .
Second row :
corresponding modelpolefigures
recalculatedfrom the ODE
Bottom row :
calculation softhe, unobserved `
polefigures {c}, f} and {z} (see
text) .
(1) The{c} pole figure (0001) shows a concentration of c-axes around Y (direction perpendicular
to the direction X of maximum elongation and perpendicular to the direction Z of
maximum shortening) and a girdle close to the YZ-plane (plane of foliation) indicating
that the investigated rock was predominantly deformed by a prism slip mechanism with a
contribution ofthe slip along rhomb and basal planes .
(2) The pole figure of the ciystallographic {a} prisms (11-20) exhibits two nearly separated
concentrations around linear fabric and the shear direction . The a-axis maximum is at the
margin ofthe pole figure with an angle of about 25° te, the foliation plane.
1 8-19