Goniometría de texturas por difracción de Rayos X, aplicación al análisis cinemático de fábricas miloníticas

Laburpena

Texture goniometry is a technique wich allows the draw of fabrics of rock-forming minerals. In the microtectonic study and specially in quartz-rich rocks of shear zones, it is of great interest the analysis of axis through the (1 1 0 ) reflections of quartz. The results have the same values that those obtained by diagrams of optical axis poles of quartz, but logically having a very different geometry, because the crystallographic elements under discussion are turned 90°. The main advantages of texture goniometry are four: First, the number of grains analyzed may be greater (thousands instead of hundreds). Second, the method is error free, due to the total automatization. The very short time required for each analysis (5 minutes) allows a great number of data, and, consequently, it is possible to make a continous study in a metamorphic series. Third, the method is better with a small particcle size, even with those unavailable under petrographic microscope. Lastly, this methos is useful for any mineral (calcite, olivine, etc.), and it is the oney practical one when we study the orientation in ore minerals. The diagrams obtained from quartz fabrics in milonitic rocks show the main values of axis in acordance with the X direction of de - formative ellipsoid. Although such direction displaces by several degres when the deformation is not coaxial. The vorticity is accuratly shown by the sense of tilting.