EUROCK 2014 Calleja et al. Textural anisotropies characterization of granitic rocks using P-wave velocities L. Calleja, A. Rodríguez-Rey, V.G. Ruiz de Argandoña and C. Camino Departamento de Geología, Universidad de Oviedo, Oviedo, Asturias, España N. Sánchez Delgado Fundación Centro Tecnolóxico do Granito do Galicia. O Porriño, Pontevedra, España ABSTRACT: Three granitic rocks from Galicia, Spain, namely Gris Alba, Albero Granite and Traspieles were petrographically (textural, mineralogy and fractography) characterized. Later, longitudinal waves velocity (Vp) in 3 orthogonal directions was determined; measurements were carried out on cubes 7 cm edge, wet and water saturated, previously oriented according to regional directions. Wet samples shows an anisotropic behaviour of Vp, however, on water saturated samples one of them behaves isotropically. From the obtained data and calculated IQ (quality index) and IF (microfissuration index), models of microcrack network distribution and possible mineral grains orientation were developed; the proposed models were compared with the petrographic studies, showing a perfect agreement between both of them. Key words: ultrasounds, Vp, anisotropy, granitic rocks. 1. INTRODUCTION The existence of textural elements orientations (mineralogy or fissuration) of rocks is sometimes difficult to detect in a simple and fast way; the small microcrack size or the low orientation grade of one or more mineral phases can make these characteristics difficult to observed with the naked eye. Obviously, microscopic studies (under optical polarizing or fluorescence microscopy and scanning electron microscopy) easily show the existence of preferred orientations. Generally speaking, granitic rocks show microcrack networks originated by their own crystallization and emplacement processes. These processes sometimes originate mineralogical orientations that may affect the entire volume of rock due to the existence of magmatic flow during the cooling processes. In other cases, the orientation is more localized at the pluton borders due to the emplacement and the fractional crystallization processes. Other granitic rocks show microcrack networks without preferred directions, with a disposition that is dense and orthogonal to a degree that depends on the contraction during the cooling process. The rock characterization by the study of the velocity of high frequency waves (ultrasounds) as well as the characteristics of the waves after travelling through the rocks is a usual technique in geological studies both in the laboratory and in the field. These are non-destructive techniques (NDT), easy to apply and very useful for the determination of the dynamic properties of the rocks. Furthermore, they provide information about the existence of anisotropies that can influence some rock properties. In the present paper the relationship between the P- wave (primary or longitudinal) velocities and the petrographic characteristics of several granitic rocks is studied; the waves are affected by the complex interaction of many rock characteristics: crystal shape and size, mineralogy, weathering degree, mineralogical composition, rock density and porosity, existence of anisotropies, joints and fractures. The P- wave velocities have been measured in both dry and water-saturated samples. With the obtained results, models of the disposition of possible anisotropies have been elaborated, which have then been contrasted with petrographic observations. Several authors have studied the relationship between wave velocity and several physical and petrographic properties of rocks. Rio et al. (2006) found a negative correlation between the accessible porosity of granites from Extremadura (Spain) and the compressive strength and wave velocity. Kern et al. (2008) and Kern & Mengel (2011) studied the relationship between foliation due to oriented micas, microcracks and P and S wave velocity in gneissic rocks. Vázquez et al. (2010) found a linear correlation between fractographic