scholarly journals Lithospheric image of the Central Iberian Zone (Iberian Massif) using Global-Phase Seismic Interferometry

2019 ◽  
Author(s):  
Juvenal Andrés ◽  
Deyan Draganov ◽  
Martin Schimmel ◽  
Puy Ayarza ◽  
Imma Palomeras ◽  
...  
Keyword(s):  
Lower Crust ◽  
Scale Model ◽  
Seismic Interferometry ◽  
Mountain Range ◽  
Iberian Massif ◽  
Central System ◽  
Duero Basin ◽  
Short Period ◽  
Single Station ◽  
Spanish Central System

Abstract. The Spanish Central System is an intraplate mountain range that divides the Iberian Inner Plateau in two sectors – the northern Duero Basin and the Tajo Basin to the south. The topography of the area is highly variable with the Tajo Basin having an average altitude of 450–500 m while the Duero Basin presents a higher average altitude of 750–800 m. The Spanish Central System is characterized by a thick-skin pop-up and pop-down configuration formed by the reactivation of Variscan structures during the Alpine Orogeny. The high topography is, most probably, the response of a tectonically thickened crust that should be also identified by 1) the geometry of the Moho discontinuity 2) an imbricated crustal architecture and/or 3) the rheological properties of the lithosphere. Shedding some light about these features are the main targets of the current investigation. In this work, we present the lithospheric-scale model across this part of the Iberian Massif. We have used data from the CIMDEF project, which consists of recordings of an almost-linear array of 69 short-period seismic stations, which define a 320 km long transect. We have applied the so-called Global-Phase Seismic Interferometry. The technique uses continuous recordings of global-earthquakes (> 120º epicentral distance) to extract global phases and their reverberations within the lithosphere. The processing provides an approximation of the zero-offset reflection response of a single station to a vertical source, sending (near) vertical seismic energy. Results indeed reveal a clear thickening of the crust below the Central System resulting, most probably, from an imbrication of the lower crust. Accordingly, the crust-mantle boundary is mapped as a relative flat interface at approximately 10 s two-way travel time except in the Central System, where this feature deepens towards the NW reaching more than 12 s. The boundary between the upper and lower crust is well defined and is found at 5 s two-way travel. The upper crust has a very distinctive signature depending on the region. Reflectivity at upper-mantle depths is scattered throughout the profile, located between 13–18 s, and probably related with the Hales discontinuity.

scholarly journals Lithospheric image of the Central Iberian Zone (Iberian Massif) using global-phase seismic interferometry

Solid Earth ◽  
2019 ◽  
Vol 10 (6) ◽  
pp. 1937-1950 ◽  
Author(s):  
Juvenal Andrés ◽  
Deyan Draganov ◽  
Martin Schimmel ◽  
Puy Ayarza ◽  
Imma Palomeras ◽  
...  
Keyword(s):  
Travel Time ◽  
Lower Crust ◽  
Scale Model ◽  
Seismic Interferometry ◽  
Iberian Massif ◽  
Central System ◽  
Duero Basin ◽  
Short Period ◽  
Single Station ◽  
Spanish Central System

Abstract. The Spanish Central System is an intraplate mountain range that divides the Iberian Inner Plateau in two sectors – the northern Duero Basin and the Tajo Basin to the south. The topography of the area is highly variable with the Tajo Basin having an average altitude of 450–500 m and the Duero Basin having a higher average altitude of 750–800 m. The Spanish Central System is characterized by a thick-skin pop-up and pop-down configuration formed by the reactivation of Variscan structures during the Alpine orogeny. The high topography is, most probably, the response of a tectonically thickened crust that should be the response to (1) the geometry of the Moho discontinuity, (2) an imbricated crustal architecture, and/or (3) the rheological properties of the lithosphere. Shedding some light on these features is the main target of the current investigation. In this work, we present the lithospheric-scale model across this part of the Iberian Massif. We have used data from the Central Iberian Massif Deformation (CIMDEF) project, which consists of recordings of an almost-linear array of 69 short-period seismic stations, which define a 320 km long transect. We have applied the so-called global-phase seismic interferometry. The technique uses continuous recordings of global earthquakes (>120∘ epicentral distance) to extract global phases and their reverberations within the lithosphere. The processing provides an approximation of the zero-offset reflection response of a single station to a vertical source, sending (near)-vertical seismic energy. Results indeed reveal a clear thickening of the crust below the Central System, resulting, most probably, from an imbrication of the lower crust. Accordingly, the crust–mantle boundary is mapped as a relatively flat interface at approximately 10 s two-way travel time except in the Central System, where this feature deepens towards the NW reaching more than 12 s. The boundary between the upper and lower crust is well defined and is found at 5 s two-way travel time. The upper crust has a very distinctive signature depending on the region. Reflectivity at upper-mantle depths is scattered throughout the profile, located between 13 and 18 s, and probably related to the Hales discontinuity.

scholarly journals Lithospheric structure of the Iberian Central System (Iberian Massif) imaged by the wide-angle seismic reflection/refraction CIMDEF experiment 

2021 ◽  
Author(s):  
Irene DeFelipe ◽  
Puy Ayarza ◽  
Imma Palomeras ◽  
Juvenal Andrés ◽  
Mario Ruiz ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Seismic Reflection ◽  
P Wave ◽  
Lithospheric Structure ◽  
Mountain Range ◽  
Wide Angle ◽  
Topographic Feature ◽  
Iberian Massif ◽  
Central System ◽  
P Wave Velocity

<p>The Iberian Central System represents an outstanding topographic feature in the central Iberian Peninsula. It is an intraplate mountain range formed by igneous and metasedimentary rocks of the Variscan Iberian Massif that has been exhumed since the Eocene in the context of the Alpine orogeny. The Iberian Central System has been conventionally interpreted as a thick-skinned pop-up mountain range thrust over the Duero and Tajo foreland basins. However, its lithospheric structure and the P-wave velocity distribution are not yet fully resolved. In order to place geophysical constraints on this relevant topographic feature, to identify lithospheric discontinuities, and to unravel the crustal deformation mechanisms, a wide-angle seismic reflection and refraction experiment, CIMDEF (Central Iberian Mechanism of DEFormation), was acquired in 2017 and 2019. It is a NNW-SSE oriented 360-km long profile that runs through the Duero basin, the Iberian Central System and the Tajo basin. First results based on forward modeling by raytracing show an irregularly layered lithosphere and allow to infer the depth extent of the northern Iberian Central System batholith. The crust is ~ 31 km thick under the Duero and Tajo basins and thickens to ~ 39 km under the Iberian Central System. A conspicuous thinning of the lower crust towards the south of the Iberian Central System is also modeled. Along this transect, a continuous and high amplitude upper mantle feature is observed and modeled as the reflection of an interface dipping from 58 to 62 km depth featuring a P-wave velocity contrast of 8.2 to 8.3 km/s. Our preliminary results complement previous models based on global-phase seismic and noise interferometry and gravity data, provide new constraints to validate the accuracy of passive seismic methods at lithospheric scale, and contribute with a resolute P-wave velocity model of the study area to unravel the effect of the Alpine reactivation on the central Iberian Massif.<br>This project has been funded by the EIT-RawMaterials 17024 (SIT4ME) and the MINECO projects: CGL2016-81964-REDE, CGL2014-56548-P.</p>

scholarly journals What can seismic noise tell us about the Alpine reactivation of the Iberian Massif? An example in the Iberian Central System

Solid Earth ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 2499-2513
Author(s):  
Juvenal Andrés ◽  
Puy Ayarza ◽  
Martin Schimmel ◽  
Imma Palomeras ◽  
Mario Ruiz ◽  
...  
Keyword(s):  
Seismic Noise ◽  
Deformation Mechanisms ◽  
Mountain Range ◽  
Foreland Basins ◽  
Iberian Massif ◽  
Central System ◽  
The North ◽  
Deep Crustal Structure ◽  
Southern Central ◽  
Lower Crustal

Abstract. The Iberian Central System, formed after the Alpine reactivation of the Variscan Iberian Massif, features maximum altitudes of 2500 m. It is surrounded by two foreland basins with contrasting elevation: the Duero Basin to the north, located at 750–800 m, and the Tajo Basin to the south, lying at 450–500 m. The deep crustal structure of this mountain range seems to be characterized by the existence of a moderate crustal root that provides isostatic support for its topography. New seismic data are able to constrain the geometry of this crustal root, which appears to be defined by a northward lower-crustal imbrication of the southern Central Iberian crust underneath this range. Contrarily to what was expected, this imbrication also affects the upper crust, as the existing orogen-scale mid-crustal Variscan detachment was probably assimilated during the Carboniferous crustal melting that gave rise to the Central System batholith. In addition, the lower crust might have thinned, allowing coupled deformation at both crustal levels. This implies that the reactivated upper-crustal fractures can reach lower-crustal depths, thus allowing the entire crust to sink. This new model can explain the differences in topography between the Central System foreland basins. Also, it provides further constraints on the crustal geometry of this mountain range, as it seems to be that of an asymmetric Alpine-type orogen, thus hindering the existence of buckling processes as the sole origin of the deformation. The results presented here have been achieved after autocorrelation of seismic noise along the CIMDEF (Central Iberian Massif DEFormation Mechanisms) profile. Although the resolution of the dataset features limited resolution (0.5–4 Hz, stations placed at ∼ 5 km), this methodology has allowed us to pinpoint some key structures that helped to constraint the deformation mechanisms that affected Central Iberia during the Alpine orogeny.

scholarly journals What can seismic noise tell us about the Alpine reactivation of the Iberian Massif? An example in the Iberian Central System

2020 ◽  
Author(s):  
Juvenal Andrés ◽  
Puy Ayarza ◽  
Martin Schimmel ◽  
Imma Palomeras ◽  
Mario Ruiz ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Noise ◽  
Mountain Range ◽  
Upper Crust ◽  
Foreland Basins ◽  
Iberian Massif ◽  
Central System ◽  
Deep Crustal Structure ◽  
Southern Central ◽  
Lower Crustal

Abstract. The Iberian Central System, formed after the Alpine reactivation of the Variscan Iberian Massif, features maximum altitudes of 2500 m. It is surrounded by two foreland basins with contrasting elevation: The Duero Basin to the N, located at 750–800 m and the Tajo Basin to the S, lying at 450–500 m. The deep crustal structure of this mountain range seems to be characterized by the existence of a moderate crustal root that provides isostatic support for its topography. New seismic data is able to constrain the geometry of this crustal root, which appears to be defined by a northward lower crustal imbrication of the southern Central Iberian crust underneath this range. Contrarily to what was expected, this imbrication also affects the upper crust, as the existing orogen-scale mid-crustal Variscan detachment was probably assimilated during the Carboniferous crustal melting that gave rise to the Central System batholith. This implies that the reactivated upper crustal fractures can reach lower crustal depths, thus allowing the entire crust to sink. This new model can explain the differences in topography between the Central System foreland basins. Also, it provides further constrains on the crustal geometry of this mountain range, as it seems to be that of an asymmetric Alpine-type orogen, thus hindering the existence of buckling processes as the sole origin of the deformation. Results presented here have been achieved after autocorrelation of seismic noise along the CIMDEF profile. Although the resolution of the dataset features limited resolution (0.5–4 Hz, stations placed at ~ 5 km), this methodology has allowed us to pinpoint some key structures that helped to constraint the deformation mechanisms that affected Central Iberia during the Alpine orogeny.

A fluid-inclusion study and genetic model of wolframite-bearing quartz veins, Garganta de los Montes, Spanish Central System

1990 ◽  
Vol 54 (375) ◽  
pp. 267-278 ◽  
Author(s):  
E. Ouilez ◽  
J. Sierra ◽  
E. Vindel
Keyword(s):  
Genetic Model ◽  
Fluid Inclusion Study ◽  
Central System ◽  
Quartz Veins ◽  
Low Salinity ◽  
Third Stage ◽  
Inclusion Study ◽  
Moderate Salinity ◽  
Spanish Central System

AbstractWolframite-bearing quartz veins from Garganta de los Montes, Madrid province, are hosted by banded gneisses that have undergone intense migmatization processes. The ore deposit is closely related to the La Cabrera granitic batholith. The veins strike 075° and dip 75°S. The mineral association includes wolframite, quartz and minor amounts of scheelite and sulphides (sphalerite, chalcopyrite, pyrrhotite, stannite and marcasite). The fluid phases associated with quartz from the vein margin (early barren quartz) and from the vein centre (late wolframite-bearing quartz) have been studied using microthermometry, scanning electron microscopy and crushing test analyses. Four hydrothermal stages have been distinguished.The earliest fluids, only recognized in the barren quartz, contain brine, daughter phase (halite) and trapped minerals. The second hydrothermal stage is characterized by complex carbonic-aqueous inclusions of low salinity (3 to 7 wt.% eq. NaC1) and low density (0.4 to 0.7 g.cm−3). They mainly homogenize into liquid between 300 and 420°C. The third stage is represented by low to moderate salinity inclusions (<9 wt. % eq. NaCl) of moderate density (0.8 to 0.96 g.cm−3), homogenizing between 120° and 330°C. The latest fluids correspond to aqueous solutions of higher salinities (H2O-NaCl, with Ca2+ and Mg2+) and densities (>1 g.cm−3), with TH ranging between 50 and 130°C. The role of the complex-carbonic aqueous fluids in the transport and precipitation of tungsten is highlighted.

Detachment faulting and late Paleozoic epithermal Ag-base-metal mineralization in the Spanish central system

Geology ◽  
1988 ◽  
Vol 16 (9) ◽  
pp. 800 ◽  
Author(s):  
Miguel Doblas ◽  
Roberto Oyarzun ◽  
Rosario Lunar ◽  
Nicolas Mayor ◽  
Jesus Martinez
Keyword(s):  
Base Metal ◽  
Late Paleozoic ◽  
Central System ◽  
Spanish Central System ◽  
Detachment Faulting ◽  
Base Metal Mineralization

scholarly journals A U‐Pb Study of Zircons from a Lower Crustal Granulite Xenolith of the Spanish Central System: A Record of Iberian Lithospheric Evolution from the Neoproterozoic to the Triassic

2006 ◽  
Vol 114 (4) ◽  
pp. 471-483 ◽  
Author(s):  
Javier Fernández‐Suárez ◽  
Ricardo Arenas ◽  
Teresa E. Jeffries ◽  
Martin J. Whitehouse ◽  
Carlos Villaseca
Keyword(s):  
Central System ◽  
Granulite Xenolith ◽  
System A ◽  
Spanish Central System ◽  
Lower Crustal ◽  
Lithospheric Evolution

scholarly journals The thermal state and strength of the lithosphere in the Spanish Central System and Tajo Basin from crustal heat production and thermal isostasy

2012 ◽  
Vol 58 ◽  
pp. 29-37 ◽  
Author(s):  
Alberto Jiménez-Díaz ◽  
Javier Ruiz ◽  
Carlos Villaseca ◽  
Rosa Tejero ◽  
Ramón Capote
Keyword(s):  
Heat Production ◽  
Thermal State ◽  
Central System ◽  
Spanish Central System

scholarly journals Short period forecasting of catchment-scale precipitation. Part I: the role of Numerical Weather Prediction

2000 ◽  
Vol 4 (4) ◽  
pp. 627-633 ◽  
Author(s):  
M. A. Pedder ◽  
M. Haile ◽  
A. J. Thorpe
Keyword(s):  
Numerical Weather Prediction ◽  
Balance Equation ◽  
Prediction Models ◽  
Weather Prediction ◽  
Phase Changes ◽  
Scale Model ◽  
Catchment Scale ◽  
Numerical Weather ◽  
Short Period ◽  
Moisture Balance

Abstract. A deterministic forecast of surface precipitation involves solving a time-dependent moisture balance equation satisfying conservation of total water substance. A realistic solution needs to take into account feedback between atmospheric dynamics and the diabatic sources of heat energy associated with phase changes, as well as complex microphysical processes controlling the conversion between cloud water (or ice) and precipitation. Such processes are taken into account either explicitly or via physical parameterisation schemes in many operational numerical weather prediction models; these can therefore generate precipitation forecasts which are fully consistent with the predicted evolution of the atmospheric state as measured by observations of temperature, wind, pressure and humidity. This paper reviews briefly the atmospheric moisture balance equation and how it may be solved in practice. Solutions are obtained using the Meteorological Office Mesoscale version of its operational Unified Numerical Weather Prediction (NWP) model; they verify predicted precipitation rates against catchment-scale values based on observations collected during an Intensive Observation Period (IOP) of HYREX. Results highlight some limitations of an operational NWP forecast in providing adequate time and space resolution, and its sensitivity to initial conditions. The large-scale model forecast can, nevertheless, provide important information about the moist dynamical environment which could be incorporated usefully into a higher resolution, ‘storm-resolving’ prediction scheme. Keywords: Precipitation forecasting; moisture budget; numerical weather prediction

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