Search

A gravimetrical study has been carried out in the North-Eastern part of the Cuadalentin Depression (Betic Cordillera) in order to obtain the structure of the basement. From the distribution and orientation of the gravimetric anomalies and their gradients, structural lineations with N40-50E and N70E orientations have been interpretated. These structural lineations are related to N40-50E and N70E blind faults in the borders and within the Depression. These faults were developed by an extensional tectonic regime recognized in this region during the Lower and Middle Miocene. Some selected faults were reactivated since the earlier Upper Miocene to current times (Current Tectonic Regime) under a compresional regime (Alhama and Carrascoy faults). These two faults and the blind associated faults are responsible of the seismicity in the borders and within the Depression. In adittion, some epicenter accumulations are related to the crossing points of these NE-SW faults and active faults with N140E orientation

A gravimetrical study has been carried out in the North-Eastern part of the Cuadalentin Depression (Betic Cordillera) in order to obtain the structure of the basement. From the distribution and orientation of the gravimetric anomalies and their gradients, structural lineations with N40-50E and N70E orientations have been interpretated. These structural lineations are related to N40-50E and N70E blind faults in the borders and within the Depression. These faults were developed by an extensional tectonic regime recognized in this region during the Lower and Middle Miocene. Some selected faults were reactivated since the earlier Upper Miocene to current times (Current Tectonic Regime) under a compresional regime (Alhama and Carrascoy faults). These two faults and the blind associated faults are responsible of the seismicity in the borders and within the Depression. In adittion, some epicenter accumulations are related to the crossing points of these NE-SW faults and active faults with N140E orientation

The RADAR interferometry (INSAR) is a modern technique that offers the possibility to identify and quantify surface displacements using phase differences from two different RADAR images (Massonnet and Feigl, 1998). The result of an interferometric study applied to the February 1 999 (Mb: 4.8) Mula (Murcia) earthquake is shown in this work. The available seismological data for this earthquake give different focal mechanisms (reverse or strike-slip mechanism) depending on the applied method. The five coseismic interferograms show that the Mula mainshock produced a very small surface deformation, less than expected for a pure reverse and swallow source. This evidence and the surface geological data support a NE-SO strike-slip fault (probably the Crevillente fault) to be the seismogenetic source

The RADAR interferometry (INSAR) is a modern technique that offers the possibility to identify and quantify surface displacements using phase differences from two different RADAR images (Massonnet and Feigl, 1998). The result of an interferometric study applied to the February 1 999 (Mb: 4.8) Mula (Murcia) earthquake is shown in this work. The available seismological data for this earthquake give different focal mechanisms (reverse or strike-slip mechanism) depending on the applied method. The five coseismic interferograms show that the Mula mainshock produced a very small surface deformation, less than expected for a pure reverse and swallow source. This evidence and the surface geological data support a NE-SO strike-slip fault (probably the Crevillente fault) to be the seismogenetic source

In this work has been analysed the 1993-1994 Adra seismic sequence characterized by two mainshocks of magnitude 5.0 and 4.9. The local neolectonic, aftershock distribution and fault plane solutions are performed and we find significant relations between them this seismic sequence respond to a "compound earthquake mechanism " caused by the reactivation of a N 170 E fault (second mainshock mb: 4.9) as a result of the first main shock ( mb: 5.0) asociated to a N 135 E oblique slip fault. The aftershock activity is acumulated into a fault bounded crustal block as a result of the field stress readjustment and changes in the pore pressure triggered off by the two mainshocks

In this work has been analysed the 1993-1994 Adra seismic sequence characterized by two mainshocks of magnitude 5.0 and 4.9. The local neolectonic, aftershock distribution and fault plane solutions are performed and we find significant relations between them this seismic sequence respond to a "compound earthquake mechanism " caused by the reactivation of a N 170 E fault (second mainshock mb: 4.9) as a result of the first main shock ( mb: 5.0) asociated to a N 135 E oblique slip fault. The aftershock activity is acumulated into a fault bounded crustal block as a result of the field stress readjustment and changes in the pore pressure triggered off by the two mainshocks

A gravity research was carried out in the SE of the Spanish Centra/ System. The upper crust has been modelled in 2 1/2 D along three profiles. The gravity models suggest that the faults affecting both the Mesozoic-Cenozoic cover and the Hercynian basement are main/y high angle inverse fau/ts. Sorne of them bound permian bassins and they are basement faults, reactivated during the alpine deformations. Key words: Gravity models, Upper Crust, Spanish Central System

A gravity research was carried out in the SE of the Spanish Centra/ System. The upper crust has been modelled in 2 1/2 D along three profiles. The gravity models suggest that the faults affecting both the Mesozoic-Cenozoic cover and the Hercynian basement are main/y high angle inverse fau/ts. Sorne of them bound permian bassins and they are basement faults, reactivated during the alpine deformations. Key words: Gravity models, Upper Crust, Spanish Central System

In this work we study the alpine fracturation affecting both the Hercynian basement and the Mesozoic/Cenozoic cover, in the Lozoya tectonic trough (Spanish Central System). From the study of the fault rocks and their associated structures, we establish a kinematic framework that allows us to deduce and corroborate the predominantly reverse character of these faults, within a regional pattern of submeridian compressive stresses En este trabajo se estudia la fracturación alpina que afecta tanto el basamento herciniano como la cubierta del Mesozoico/Cenozoico, en la fosa tectónica del Lozoya (Sistema Central Español). A partir del estudio de las rocas de las fallas y las estructuras asociadas, podemos establecer la infraestructura cinemática que nos permite deducir y corroborar la naturaleza predominantemente inversa de estas fallas, dentro de un patrón regional de esfuerzos compresivos submeridianos.

In this work we analyze the kinematics of the Alhama de Murcia fault and other fracturation systems in the area of Lorca-Totana. An alternance of NW-SE to NNE-SSW shortening directions can be identified from the Messinian to the present. This seems to be a consequence of intermittent activity along the Palomares fault (NNE-SSW), inducing changes in the trajectories of the NW-SE directed regional stress field., En este trabajo se analiza la cinemática de la falla de Alhama de Murcia y otros sistemas de fracturación en el área de Lorca-Totana. Se puede identificar una alternancia de direcciones de reducción de NO-SE a NNE-SSO desde el Messiniense hasta la actualidad. Esto parece ser una consecuencia de la actividad intermitente a lo largo de la falla de Palomares (NNE-SSO), induciendo cambios en las trayectorias del campo de tensión regional dirigido NO-SE.

In this work we analyze the kinematics of the Alhama de Murcia fault and other fracturation systems in the area of Lorca-Totana. An alternance of NW-SE to NNE-SSW shortening directions can be identified from the Messinian to the present. This seems to be a consequence of intermittent activity along the Palomares fault (NNE-SSW), inducing changes in the trajectories of the NW-SE directed regional stress field. En este trabajo se analiza la cinemática de la falla de Alhama de Murcia y otros sistemas de fracturación en el área de Lorca-Totana. Se puede identificar una alternancia de direcciones de reducción de NO-SE a NNE-SSO desde el Messiniense hasta la actualidad. Esto parece ser una consecuencia de la actividad intermitente a lo largo de la falla de Palomares (NNE-SSO), induciendo cambios en las trayectorias del campo de tensión regional dirigido NO-SE.

In this work we study the alpine fracturation affecting both the Hercynian basement and the Mesozoic/Cenozoic cover, in the Lozoya tectonic trough (Spanish Central System). From the study of the fault rocks and their associated structures, we establish a kinematic framework that allows us to deduce and corroborate the predominantly reverse character of these faults, within a regional pattern of submeridian compressive stresses, En este trabajo se estudia la fracturación alpina que afecta tanto el basamento herciniano como la cubierta del Mesozoico/Cenozoico, en la fosa tectónica del Lozoya (Sistema Central Español). A partir del estudio de las rocas de las fallas y las estructuras asociadas, podemos establecer la infraestructura cinemática que nos permite deducir y corroborar la naturaleza predominantemente inversa de estas fallas, dentro de un patrón regional de esfuerzos compresivos submeridianos.

[Resumen] El presente trabajo concierne a la aplicación de estudios geo16gicos y tectónicos en la prospección minera de determinadas masas de sulfuros en Aznalcollar, región oriental de la Banda Piritosa Ibérica. Del análisis de datos petrológicos, sedimentarios y tectónicos, se ha podido establecer: 1°) El control estratigráfico y las facies favorables de las rocas encajantes de las masas de sulfuros. 2°) La estructura imbricada como resultado de deformación polifásica. Se describe las diferentes relaciones entre el plegamiento y cabalgamiento 3°) Secuencia litoestratigráfica del complejo volcánico sedimentario de la zona, a partir del cual, las masas de sulfuros al sur (Higuereta-Cuchichón) y la del norte (Caridad) corresponden a un mismo horizonte mineralizado. [Abstract] The present work is concerned to the application of the geological-tectonic studies on mining prospection of specifyed massive sulphide orebodies from Aznalcollar area, eastern region of the Iberian Pyrite Belt. Analyses of petrological, sedimentary, and tectonic data, habe make known : 1°) The lithostratigraphic controls and favourable facies of the close host-rocks.2°) The imbricated structure as result of poliphase deformation, in wichthe relationships between folding and thrusting are debated. 3°) .Lithostratigraphic secuence of volcanic-sedimentary complex, in wich massive sulphi de orebodies on the north side of the Aznalcollar area (Caridad Mine) and (Higuereta-Cuchich6n Mines) to the south, are related to the same volcanic-sedimentary layer.

RESUMEN: En el presente trabajo se presta atención a los efectos de la zona de cizalla dúctil de Juzbado-Penalva do Castelo sobre las estructuras resultantes de la tectónica polifásica hercínica y granitoides. Se describen rotaciones de estratos a partir de su orientación original y de ejes-b de pliegues de las principales fases de plegamiento. A fin de contribuir al conocimiento de las variaciones de las texturas y microestructuras con la deformación, se establecen secuencias miloníticas como resultado del cizallamiento de los granitoides. Los cambios microestructurales de sus componentes incluyen: para el cuarzo, reducción del tamaño de grano durante la recristalización; en el feldespato potásico, fracturación, granulación seguida de incipiente recristalización; en la plagioclasa, deformación de maclas y fragmentación; en la biotita, planos de kink y recristalización.

[ES] La banda de milonita de Toledo responde a una zona de cizallamiento dúctil, la cual se desarrolló al final de la orogenia hercinica. Esta zona de cizalla separa rocas migmatíticas de una cobertera de metasedimentos del Paleozoico inferior y rocas graníticas. Al norte de la zona de cizalla de Toledo, las migmatitas de facies anfibolita han experimentado deformación dúctil, resultando, finalmente, en milonitas. En este trabajo se presta atención a las texturas y microestructuras que se desarrollan en las migmatitas como resultado de combinados mecanismos de deformación dúctil y frágil. Cuatro estados de deformación han sido seleccionados sobre la base del tamaño de grano del cuarzo. Para la descripción de la evolución microestructural con el aumento de la deformación en migmatitas, se exponen las microestructuras características y rasgos ópticos de deformación de los diferentes minerales para cada uno de estos estados. Un estudio comparativo entre el comportamiento mecánico del cuarzo y el feldespato fue también llevado a cabo, indicando que bajo condiciones de facies metamórfica de los esquistos verdes, el contraste entre el comportamiento dúctil del cuarzo y el comportamiento frágil del feldespato es un factor esencial, controlando los procesos de deformación en la zona de cizalla de Toledo., [EN] The Toledo mylonite belt respond to ductile shear zone which developed during the final tectonic event in the hercinian orogenic. This shear zone separates migmatites rocks from lower Palaeozoic metasediments cover and granitic rocks. On the north side of the Toledo shear zone, the amphibolite facies migmatites have undergone ductíle deformation resulting ultimaíely in mylonites. In the present study, attention is given to the textures and microstructures which develqped in the migmatites as result from combined ductile an brittle deformation mechanisms. Four stages have been selected on the basis of quartz grain size. Por a description of the microstructural evolution in the migmatites with increasing strain, the different minerals show characteristic microstructures and optical straín features in each of these stages. A comparative study between the mechanical behaviour of quartz and feldspars was also made, indicating that, under green-schist facies metamorphic conditions, the contrast between the ductile behaviour of quartz and the brittle behaviour of feldspars is the essential factor controlling deformation processes in the Toledo shear zone.