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 largescale process involving the whole lithosphere during Variscan cycle.
The historical centre of Oporto (Portugal), designated a UNESCO World Heritage of the Humanity, has been selected to illustrate the use of the local granite during the development of the city, invariably influencing the history, architecture, religion, culture and the personality of the local people.The Oporto monumental heritage goes back to Roman occupation: the city has been developed by the construction of granite buildings strongly implanted on a hard granite substrate. The Oporto profile gives an impressive grey architecture according to different styles of granite work that characterize the city in all its aspects. The description of selected sites within the historical centre, where it is possible to recognize the importance of the granite in the character of the city, aims to call attention to the inextricable role of geology in the built heritage and culture, as well as to diagnose the deterioration processes, enhanced by the environment and the anthropogenic activity, that affect houses and monuments as a consequence of the intrinsic properties of the granite. The Oporto granite genesis, responsible for the nature of the mineralogy assemblage, the physical properties and the degree of weathering, provides specific features that make this granite particularly suitable for the ornamental work that defines the town monumental constructions. The old city wall, the medieval and baroque churches, the neoclassic houses and also the small humble habitations are a few examples of the profuse stone heritage of which Oporto is proud.
In the Mirandela area, tungsten (Pedra Luz and Lombo da Veiga) and silver-gold (Freixeda) ore deposits are found which constitute a presumed example of zoning associated with Hercynian leucogranites. This peri-granitiç zoning was checked using microthermometry and Raman spectroscopic analysis of fluid inclusions in the prebearing quartz veins.
In the Pedra-Luz and Lombo da Veiga scheelite-bearing quartz veins, fluids are rich in almost pure CO2 (ZCO2, 91-100 % ; XCO2, 13-28 mole %), but no CO2 has been detected at Freixeda. However, small amounts of CH4 and N2 have been detected in the latter deposit (ZCH4, 62-100 % ; XCH4, 0.42 mole % ; ZN2, 0-38 % ; XN2, 0.26 mole %). The fluids of the three ore deposits have low densities and salinities (Pedra-Luz d=0.64, 4 wt. % NaCl eq. ; Lombo da Veiga d=0.52, 3.5 wt. % NaCl eq. ; Freixeda d=0.73, 3.8 wt. % NaCl eq.). The trapping pressures are close to 700 bars in the W ore deposits and close to 300 bars in the Ag-Au deposit. The probable trapping temperatures range from 325 to 350 °C at Pedra-Luz, 375 to 400 °C at Lombo da Veiga and 310 to 330 °C at Freixeda.
Assuming that the fluid phase was in equilibrium with graphitic material present in host metasedimentary rocks, fO2 is estimated between 10-21 and 10-20 bar, close to the Ni-NiO buffer on the basis of the equilibrium C+O2 ⇌ CO2. At Freixeda, a lower fO2 closer to the Q-F-M buffer is indicated (occurrence of CH4).
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