STRUCTURAL GEOLOGY

Author: HILARIO ORÚS ASIER.
Year: 2003.
University: PAÍS VASCO [www.ehu.es].
Place of defense: FACULTAD DE CIENCIAS Y TECNOLOGÍAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The dissertation submitted studying the internal structure of plutones of Posets and Lys, located in the central area of the zone Axial Pyrenees. The petrológico and structural study has been carried out using techniques of classical field, and microscopic study by ASM, which has allowed propose different models for each location massif, both in terms transpresivas. Massif Posets recorded essentially structures magmatic origin and its intrusion reached levels cortical surface under conditions of pressure around 150 MPa. Instead, the massif de Lys consists of structures by deformaicón in solid majority and their level of initial deployment was deeper, according to obtaining maximum pressure of approximately 400 MPa for the crystallization of the pair anfíbol-plagioclasa. The models proposed site fall into a structure in bloom positive, reflecting the conditions transpresivas the main phase (D2) hercínica in which it has summoned both plutones.

Author: GARCIA IZQUIERDO BEATRIZ.
Year: 2004.
University: COMPLUTENSE DE MADRID [www.ucm.es].
Place of defense: FACULTAD CC. GEOLÓGICAS.
Place of preparation: FACULTAD DE CIENCIAS GEOLÓGICAS.

Summary: The resort of Cabo Ortegal appear three massifs of ultramafic rocks, Limo, Herbeira and Uzal, representing a sheet of origin mantélico emplaced during orogeny Varisca. Massif Herbeira shows a greater variety and lithological features mineralization of Cr-EGP. In this massif have mapped five units litoestratigráficas principal, which appear divided into two sections separated by a zone of ductile shear direction NNE-SSO, which has been dubbed Area shears Trans Herbeira (ZCTH). The study of mineral quimismo reflects differences petrogenéticas between the western and eastern sectors. The lithologies of Sector West show generally compositions for Cr-rich spinel, while the eastern sector of lithologies are characterized by rich spinel scattered in Al. The relationship # cr in spinel, indicative of the degree of partial melting, which reflects the lithologies from one sector and another has been generated by different rates of fusion mantélica. The chemical composition of amphiboles shows differences in peridotitas of both sectors. The amphiboles in the western sector show contained minor K20 and Ti02 (% by weight) than amphiboles of peridotitas the eastern sector. In relating the contents in K20 of amphibole with the values of the relationship cr # spinel, it is noted that in the western sector dominated by merger processes while in the eastern sector of molten infiltration has been extended and the rate of fusion partial much lower than in the western sector. All peridotitas of Herbeira are characterized by enrichments in LILE and LREE, and strong empobrecimientos NB and Zr. These geochemical characteristics along with other data presented in memory, allowing interpret a geodynamic environment for root arc on a subduction zone for the formation of peridotitas. In such environments joining the wedge mantélica of molten rich volatile from the subducting plate, producing reactions of the type fundido-roca might explain the formation of harzburgitas and dunitas massif of Herbeira through replacement by the piroxenos olivinos. The structures recognized at different scales in the massive differences have allowed us to at least three phases of deformation. A high temperature deformation developed in a position mantélicas (MORE 1000 Â ° C), and two stages of deformation of high pressure and high temperature (-850Â ° C). All recognized deformation occurring in a regime of non-ductile shear coaxial, where displacement of the blocks ceiling has occurred towards the NNE, depending on the geographic coordinates of today. Data obtained from the study of the petrofábrica tell us that the main deformation occurred in conditions of moderate temperature, although there are factories relícto of phase deformation of very high temperature. The phases of deformation of high pressures and high temperatures were in a position hidratas as reflected systems sliding olivine activated during deformation. Moreover factories of clinopiroxenos indicate that the deformation regime acted in a field near the constriction. In view of all data cbtenidos in the course of this research we can conclude that the peridotitas representing massif Herbeira were formed in an environment of geodynamic arc in the root zone suprasubducción.

Author: GRIERA ARTIGAS ALBERT.
Year: 2004.
University: AUTÓNOMA DE BARCELONA [www.uab.es].
Place of defense: FACULTAT DE CIÈNCIES.
Place of preparation: ESCUELA DE POSTGRADO.

Summary: This thesis focuses on classic theme of the Structural Geology such as the folding of layers and the dynamics of particles isolated but the vast amount of work on these topics has never posed a study on the mechanics of the transition between geometric layers competent thick homogeneous bodies and isolated. This transition can be represented by layers with thickness distribution is not constant. The main objective is to identify the factors that control the mechanics of the folding of layers with thickness is not uniform and recognize the relationship between the asymmetry of these folds and kinematics of the deformation. The working method is based on a combination of detailed field studies of these structures and simulation models through theoretical, numerical and experimental materials analog. Variables in the study are the geometry of the initial layer, the mechanical properties of the medium and kinematics of the deformation. The study was based on both the analysis of the changes in geometry developed in layers, as in the distribution of the components of kinematics in and around disturbance. The results have enabled and the viability of the transition between mechanical folding structures and dynamics of particles. This is abrupt and asymmetrical, and largely dominated by the processes of buckling layer. The results are used to define three new methods of analysis of the deformation and the cumulative number of vorticity of kinematics through field data. These methods are based on the combination of simple geometric parameters such as angle of the flanks of the folds or the boudines and guidance of the foliation regard the external envelope layer. The methods are applied in the area of field, obtaining similar results for all of them. The values obtained were contrasted by other estimation methods based on the geometry of folds. The results of fields are consistent with previous interpretations of the area, and the deformation D2 consistent with a regime transpresivo with vertical extension, reduction in the area of the horizontal section and shortening the overall direction NNE-SSW. But the nature of this deformation is not stationary, with a variation of the degree of non coaxilidad between zones of low and high intensity of deformation finite.

Author: CANTO TOIMIL NOEL.
Year: 2004.
University: OVIEDO [www.uniovi.es].
Place of defense: FACULTAD DE GEOLOGÍA.
Place of preparation: FACULTAD DE GEOLOGÍA.

Summary: Knowledge of the changes in the geometry of a layer during the process of folding and deformation domestic partner is one of the major objectives of Structural Geology. This thesis deals with the study of these aspects in folds symmetrical profiles developed in layers competent terms kinematic and geometric, which implies an analysis of displacement experienced by the particles that make up the environment and the continued use of a characterization Geometric appropriate. This analysis requires the study of deformation patterns or kinematic folding mechanisms, each representing one of the ways by which accommodates deformation in the folded layers. It has proceeded on the theory prior to establish the transformations that produce longitudinal deformation mechanisms kinematic tangential (DTL), flexural flow (FF) and deformation homogeneous irrotacional (DH). These changes have been automated in a new version of the software already exists FoldModeler built environment "MATHEMATICA" TM, so that from an initial layer defined by a grid of points with known coordinates, and applying a certain sequence mechanism folding, you get the final layer collapsed with the new positions of each of the grid points. With FoldModeler has been discussed on the one hand, the geometry of the folded layers and characteristics of the deformation associated with each mechanism for folding and complex combinations of them (Direct problem), and for another, real examples of folds where the sequence has identified approximately mechanism responsible for the accommodation of the deflection in the crease real issue (inverse problem). The latter has been carried out by adjusting the actual fold with a fold theoretical done FoldModeler whose geometry and characteristics of the deformation similar to that with real-fold. The folds and studied included numerical examples of folds (obtained through analysis of Continuous Fast Lagrangian (FLAC TM) and the finite element method), pleats and folds pilot's natural NOT on the Iberian Peninsula. Knowing the mechanical properties of numerical and experimental folds has made it possible to relate the geology of the materials with the geometry of the fold and patterns of distortion. The study's principal problem with FoldMoldeler, and checking with the analysis of the folds numerical and experimental natural shows that the sequence of folding mechanisms responsible for the accommodation of deformation in the folds can be estimated from the change that experience with the dip of the layer, the direction of the major axis of the ellipse finite deformation and the ratio between the axes of the ellipse, as well as from the shape of the layer bequest. For the analysis of this last aspect has been used a diagram allows the classification of a set of flank pleats and the observation of the changes in the shape of the folded layers with the progress of folding patterns for different sequences of deformation. The resolution of the inverse problem has shown that, although there are endless sequences of mechanisms that can accommodate the deformation in the folds, all of which are very similar and replied to a similar evolutionary pattern. The sequence begins with shortening initial homogeneous layer, followed by a later stage with DLT I FF. The transition from one phase to another is gradually decreasing gradually shortening the amount of homogeneous and increasing accommodation of the deflection by the other two mechanisms. In the second stage, the DFT is usually the dominant mechanism although the relationship DFT / FF will diminish as folding progresses. In stages f 8 inales d 723 and development of the fold is a new episode of homogeneous deformation (crush). The beginning of this stadium, crushing can act simultaneously with LVD and FF going to represent the single facility in later stages. The importance of the different patterns of distortion is a function of the mechanical characteristics of the folds (contrast viscosity and anisotropy), and shortening of the total suffered. This has been used to develop a graphical method for the estimation of contrast viscosities and the anisotropy of the layer knowing the sequence of folding mechanism that accommodate the deformation within a fold and shortening total production. More detailed studies carried out on the folds reveal that there is heterogeneity in the distribution of mechanisms through layer with a greater intensity FF towards the central parts of the same, and that LVD is serving as a "DLT attenuated" thus has a pattern of distortion through the layer characterized by an intensity of deformation smallest of what to expect as the classic definition of the mechanism.

Author: GONZALEZ CUADRA PABLO.
Year: 2004.
University: SALAMANCA [www.usal.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The unit Corredoiras is one of the higher pressure units intermediate complex orders, which is in the complex alóctonos of Galicia and northern Portugal, the largest and the most units are represented in this group. It consists of lithologies ortoderivadas type ácido-intermedio and basic covering enclaves metasedimentos nature pelítica and grauwáquica. It has a complex structure in which it has distinct groups of five accidents or major accidents, which are arranged chronologically: the takeoff of Queimada, cabalgamientos Ductile the uptake of Corredoiras, the folds of Sobrado, Bocelo, Belmil and Santiso and takeoff of Boimorto. The granulitas pelíticas and shale, which are part of the enclaves of metasedimentos and metagabros and amphibolites, representing most of the bodies of metabasitas distributed throughout the unit, reveal new information about the geological history of unity . The metamorphic changes observed in both types litológicos is compatible and reflects the influence of two events tectonotérmicos progrados: one in facies of the granulitas and another in the facies amphibolites. The combination of structural analysis and petrológico shows that the unit Corredoiras recorded an evolution policíclica which includes two cycles of burial and exhumation, which happen other episodes compressive, extensional and tear that have a minor in the evolution metamorphic, but a decisive condition of the current structure of the unit. The ages available show that the integration of lithologies comprising the unit and the first orogenic cycle occur in a short period of time during the Lower Ordovician, while the second orogenic cycle occurs during Devónico, partly in anticipation cycle Varisco Iberian Massif, during which produces the location of the complex alóctonos, they acquired its current configuration.

Author: GOMEZ BARREIRO JUAN.
Year: 2004.
University: SALAMANCA [www.usal.es].
Place of defense: EDIFICIO HISTORICO.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: The study of the evolution tectonometamórfica OS Complex Order (NO Iberian Massif) has been carried out by integrating data from structural geology, petrology and metamorphic geocronología. Obtaining a complete geological sequence of events has shown that the units tectonometamórficas comprising Complex has received three cycles orogénicos: Cambro-Ordovícico, Silúrico and Devono-Carbonífero. Analysis Unit Fornás (unit alochthonous senior AP-AT) has given the keys necessary for the completion of a geodynamic model of regional validity. This unit represents the levels of transition from one element litosférico exotic, a magmatic arc. The results show a first major event burial in the allochthonous units above. In the case of unit Fornás-Arinteiro be able to reach the granulitos high pressure (13-15 kbar / 700-800Â ° C), while in the units of medium pressure (U. of O Pine) conditions are those of facies of amphibolites (10 kbar/650Â ° C). After this event both units were put in touch through takeoff extensional Fornás, with a kinematic motion of the block toward the ceiling NW. This event gives rise to a strong decompression isotherm of rocks block wall (U. of Fornás) followed by cooling at low pressure, while the block roof (U. of O Pine) is a warming of Based on low pressure. The activity has been datada takeoff at 420 ma By Ar-Ar. The launch of Fornás appears doubling by folds and lay cut by cabalgamientos with kinematics towards JAN. This new episode of burial leads to partnerships programs in the shears (7-8 kbar / 450-550 Â ° C). Its activity has been datada at 395 ma (Ar-Ar). Finally Takeoff of Bembibre-Pico Holy accommodates the gravitational collapse.