MICROTEXTURE EVALUATION WITH LAUE DIFFRACTION. Heidelbach, F.¹, Wenk, H.R.^2,3, Chateigner, D.^2,3 and Zontone, F.¹, ¹European Synchrotron Radiation Facility, B.P. 220, Grenoble, France, ²Laboratoire de Cristallographie, CNRS, Grenoble, France, ³Department of Geology and Geophysics, University of California, Berkeley, U.S.A

An fully automated procedure was developed for orientation determination of single crystals from Laue diffraction patterns generated by synchrotron radiation. The diffraction patterns were formed with a highly focused X-ray beam (10-30 micrometer) from a thin slab (100 micrometer) of material in transmission geometry. The fully computerized recognition of zones was achieved by transformation of the Laue pattern into a gnomonic projection (where zones are straight lines) and the subsequent application of the Hough transform for line identification. The orientation at each data point was then determined by comparison of angular relationships between zones with a standard table for the known structure. The fully automated procedure allows for rapid orientation determination of single crystals which is particularly important for microtexture analysis. Similar measurements with electron diffraction in the electron microscope are restricted to thin, relatively undeformed surface layers whereas the Laue patterns contain information about a much larger volume which may be considerably deformed. The advantages of the method are demonstrated with the analysis of the microtexture of an olivine rich peridotite from the upper mantle.