Los efectos térmicos del Complejo Plutónico de Santa Eulalia (sur de Portugal) en las rocas metaígneas y metasedimentarias encajantes

The Santa Eulália Plutonic Complex (SEPC) is a late-Variscan granitic body located in the northern part of the Ossa Morena Zone, a inner zone of the Variscan Iberian Massif. The SEPC host rocks are composed of meta-igneous and metasedimentary units, from Upper Proterozoic to Paleozoic ages, with a NW-SE structure, cross-cut by the SEPC. The SEPC host rocks, with low grade metamorphism show well preserved primary sedimentary or igneous mineralogical, textural and structural features. The thermal effect induced by the SEPC is restricted to the roof pendants. At N and NE of the SEPC, textures and paragenesis resulting from thermal metamorphism, are not related to the SEPC intrusion but to a previous magmatism, controlled by the NW-SE regional anisotropies. The restriction of the thermal effects to the pluton roof may be caused by a combination of several interrelated factors: higher volume of granitic mass, thermal effect by advection of fluids and longer period of prevalence of high thermal conditions. The geochemical study of SEPC host rocks shows the heterogeneous character and diversity of metasedimentary, igneous and meta-igneous rocks. The whole rock geochemical data indicate that all the metasedimentary lithologies derived from an upper continental crustal source and the igneous and meta-igneous rocks show no evidence of metasomatic effects by the SEPC emplacement.El Complejo Plutónico de Santa Eulalia (CPSE) es un cuerpo granítico tardi-Varisco situado en la parte norte de la Zona de Ossa Morena, en la zona interior del Macizo Ibérico Varisco. Las rocas encajantes del CPSE están compuestas por unidades meta-ígneas y metasedimentarias, de edades que van desde el Proterozoico Superior hasta el Paleozoico, con una estructura de dirección NW-SE, cortada por el CPSE. Las rocas encanjantes del CPSE, con metamorfismo de bajo grado conservan estructuras, mineralogía y textura primarias. El efecto térmicoinducido por el CPSE se limita a los roof pendants. Al N y NE del CPSE, las texturas y paragénesis resultantes del metamorfismo térmico, no están relacionadas con la intrusión del CPSE sino con un magmatismo anterior, controlado por anisotropías regionales NW- SE. La restricción de los efectos térmicos al techo del pluton puede ser causada por una combinación de varios factores interrelacionados: mayor volumen de masa granítica, un efecto térmico por la advección de fluidos y el período de prevalencia de altas condiciones térmicas. Los datos geoquímicos de las rocas encanjantes del CPSE muestran el carácter heterogéneo y la diversidad de rocas sedimentarias, metasedimentarias, ígneas y meta-ígneas. El análisis de los datos geoquímicos indica que todas las litologías sedimentarias y metasedimentarias han derivado de la corteza continental superior, mientras las rocas ígneas y meta-ígneas tienen una composición que no muestra evidencias de efectos metasomáticos por el emplazamiento del CPSE

The national inventory of geological heritage: methodological approach and results

A existência de um inventário nacional de património geológico é fundamental para se poderem implementar estratégias de geoconservação. Este trabalho apresenta a metodologia usada no desenvolvimento do mais completo inventário de geossítios, realizado até ao momento em Portugal, assim como os principais resultados obtidos. O inventário vai integrar o Sistema de Informação do Património Natural e o Cadastro Nacional dos Valores Naturais Classificados, ambos geridos pelo Instituto de Conservação da Natureza e da Biodiversidade.The existence of a national inventory of the geological heritage is of paramount importance for the implementation of a geoconservation strategy. This paper presents the methodological approach used to produce the most complete geosites inventory in Portugal, so far, and the obtained results. This inventory will be uploaded into the National Database of Natural Heritage managed by the Portuguese authority for nature conservation.Este trabalho é apoiado pela Fundação para a Ciência e a Tecnologia, através do financiamento plurianual do CGUP e do projecto de investigação “Identificação, caracterização e conservação do património geológico: uma estratégia de geoconservação para Portugal” (PTDC/CTE-GEX/64966/2006).info:eu-repo/semantics/publishedVersio

Building up of a nested granite intrusion: magnetic fabric, gravity modelling and fluid inclusion planes studies in Santa Eulália Plutonic Complex (Ossa Morena Zone, Portugal)

AbstractThe Santa Eulália Plutonic Complex (SEPC), located in the Ossa Morena Zone (south Portugal), is composed of a medium- to coarse-grained pink granite (G0-type) and a central grey medium-grained biotite granite (G1-type). Available Rb–Sr data indicates an age of 290 Ma. An emplacement model for the SEPC is proposed, taking into account magnetic fabric, 2D gravity modelling and fluid inclusion planes studies. The G0 and G1 types demonstrate different magnetic behaviour: G0 is considered a magnetite-type granite and G1 is an ilmenite-type granite. The formation of G0 required oxidized conditions related to the interaction of mafic rocks with a felsic magma. The 2D gravity modelling and subvertical magnetic lineations show that the feeder zone of the SEPC is located in the eastern part of the pluton, confirming the role of the Assumar and Messejana Variscan faults in the process of ascent and emplacement. The magma emplacement was controlled by ENE–WSW planar anisotropies related to the final brittle stages of the Variscan Orogeny. The emplacement of the two granites was almost synchronous as shown by their gradational contacts in the field. The magnetic fabric however suggests emplacement of the G0-type first, closely followed by emplacement of the G1-type, pushing the G0 laterally which becomes more anisotropic towards the margin. The G1-type became flattened, acquiring a dome-like structure. The SEPC is a nested pluton with G0-type granite assuming a tabular flat shape and G1-type forming a rooted dome-like structure. After emplacement, SEPC recorded increments of the late Variscan stress field documented by fluid inclusion planes in quartz.</jats:p

Variscan Magmatism

This chapter aims to identify, characterize and locate the main facts/events related to orogenesis in the Iberian Peninsula. Its succession in space and time determines the geodynamic environment of the broader geological phenomenon corresponding to the Variscan cycle. In this sense, this section comprises two parts: I—The Iberian orogenic magmatism seen through a space-time approach of its westernmost region—focus on the enormous complexity of the inherited basement, its nature, age and distribution in space. Establishes a space-time sequence of geodynamic environments correlated with the obtained data and tries to identify the agents responsible for its genesis. Some case studies are presented to illustrated significant regional aspects of the magmatic process and II—An overview of the petrogenesis of the great batholiths and of the basic, intermediate and mantle-related rocks—identify and analyze a great amount of these rocks intruding and extruded from 400 to 280 Ma and to better understanding the large-scale process involving the whole lithosphere during Variscan cycle.publishe