Ore prospecting in the Iberian Pyrite Belt using seismic and potential-field data

Carvalho, João P. G.; Sousa, Pedro; Matos, João Xavier; Pinto, Carlos C.

doi:10.1088/1742-2132/8/2/002

Cited by 10 publications

(8 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Heat production values were obtained in the present work using appropriate density values for the region reported by Carvalho, Sousa, Matos and Pinto (2011) and Silva (2015). The concentrations of U, TH and K were presented in Barberes et al (2014).…”

Section: Heat Production In the Crustmentioning

confidence: 99%

Heat Flow, Geotherms, Density and Lithosphere Thickness in SW of Iberia (South of Portugal)

Duque

2018

ijthfa

View full text Add to dashboard Cite

Thermal structure, density distribution and lithosphere thickness in the SW part of the Iberian Peninsula are studied using data obtained in the South Portuguese Zone (SPZ) and SW border of the Ossa Morena Zone (OMZ) in the South of Portugal. Five different regions were defined, and models were built for each region. Geotherms were obtained using average density values from data published. The high values of heat flow density in these regions are attributed to occurrence of anomalous heat sources due to radioactivity content and exothermic chemical reactions associated to ore deposits in the zone. The results obtained with models based on isostasy in the region led to lithosphere thickness values between 95 and 96 km in the SPZ and a lower value of 94.5 km in the SW border of the OMZ. Analysis of geotherms shows lateral variations of temperature at the same depth. These lateral variations are compared with information obtained with seismic data.

show abstract

Section: Heat Production In the Crustmentioning

confidence: 99%

Heat Flow, Geotherms, Density and Lithosphere Thickness in SW of Iberia (South of Portugal)

Duque

2018

ijthfa

View full text Add to dashboard Cite

show abstract

“…The VFX fault zone has clear expressions in the potential field data (Carvalho et al, 2008(Carvalho et al, , 2011 and oil-industry P-wave seismic reflection data (Rasmussen et al, 1998;Carvalho et al, 2005). Several fault segments at depths beyond 40 m were interpreted based on P-wave seismic reflection and borehole data (Carvalho et al, 2006).…”

Section: Geologic Setting and Previous Workmentioning

confidence: 99%

Earthquake-faulting-related deformation in soil evidenced in S-wave shallow reflection data: Field results from Portugal

et al. 2016

Self Cite

View full text Add to dashboard Cite

Expressions of ductile, soft-sediment deformations induced by ground movements due to past earthquakes are difficult to recognize in near-surface soils. We have carried out shallow S-wave reflection studies in a seismically active area located northeast of metropolitan Lisbon, Portugal. Identifying shallow disturbed zones and hidden fault segments in this area is important but quite difficult because of small vertical slips due to earthquakes, the Holocene alluvial cover hiding the fault segments, and a high rate of surficial sedimentation. We have performed S-wave reflection profiling at two sites -Vila Franca Xira and Castanheira de Ribatejo. We detected different but interrelated evidence of soft-sediment deformation in the seismic data. This evidence includes sharp lateral changes in the S-wave velocity field; changes in the reflection horizons in stacked sections; aligned diffractions in unmigrated sections; discontinuities in common-offset gathers; and discontinuities, backscattered, and diffracted arrivals in common-source gathers. Though not equally clear everywhere, this evidence is recognizable at many locations where earthquake-motion-induced disturbed zones are interpreted. To confirm these interpretations, we have performed synthetic modeling of a seismic wavefield using the same acquisition geometry as in the field experiments, and with multiple disturbed zones present as vertical emplacements through horizontally lying soil layers. The modeling results resemble the observations in field data. It is possible to confirm the signatures of soft-sediment deformation in the shallow S-wave reflection data. The approach that we used will be useful in many seismically active, soilcovered areas in the world.

show abstract

“…Gravimetric data are well suited to estimate the depth to the base of Cenozoic due to the large density contrast between these units and underlying Mesozoic or Palaeozoic rocks (e.g. Dobrin & Savitt, ; Carvalho et al ., ,b). 2.5D gravimetric modelling was, therefore, used to estimate the base of the Cenozoic in Area II where no seismic coverage exists.…”

Section: Methodsmentioning

confidence: 99%

Tectonic evolution of an intraplate basin: the Lower Tagus Cenozoic Basin, Portugal

et al. 2016

Self Cite

View full text Add to dashboard Cite

This article focuses on the reinterpretation of well, seismic reflection, magnetic, gravimetric, surface wave and geological surface data, together with the acquisition of seismic noise data to study the Lower Tagus Cenozoic Basin tectono‐sedimentary evolution. For the first time, the structure of the base of the basin in its distal and intermediate sectors is unravelled, which was previously only known in the areas covered by seismic reflection data (distal and small part of intermediate sectors). A complex geometry was found, with three subbasins delimited by NNE‐SSW faults and separated by WNW‐ESE to NW‐SE oriented horsts. In the area covered by seismic reflection data, four horizons were studied: top of the Upper Miocene, Lower to Middle Miocene top, the top of the Palaeogene and the base of Cenozoic. Seismic data show that the major filling of the basin occurred during Upper Miocene. The fault pattern affecting Neogene and Palaeogene units derived here points to that of a polyphasic basin. In the Palaeogene, the Vila Franca de Xira (VFX) and a NNE‐SSW trending previously unknown structure (ABC fault zone) probably acted as the major strike‐slip fault zones of the releasing bend of a pull‐apart basin, which produced a WNW‐ESE to NW‐SE fault system with transtensional kinematic. During the Neogene, as the stress regime rotated anticlockwise to the present NW‐SE to WNW‐ESE orientation, the VFX and Azambuja fault zones acted as the major transpressive fault zones and Mesozoic rocks overthrusted Miocene sediments. The reactivation of WNW‐ESE to NW‐SE fault systems with a dextral strike‐slip component generated a series of horsts and grabens and the partitioning of the basin into several subbasins. Therefore, we propose a polyphasic model for the area, with the formation of an early pull‐apart basin during the Palaeogene caused by an Iberia–Eurasia plates collision that later evolved into an incipient foreland basin along the Neogene due to a NW‐SE to WNE‐ESE oriented Iberia–Nubia convergence. This convergence is producing uplift in the area since the Quaternary except for the Tagus estuary subbasin around the VFX fault, where subsidence is observed. This may be due to the locking or the development of a larger component of strike‐slip movement of the NNE‐SSW to N‐S thrust fault system with the exception of the VFX fault, which is more favourably oriented to the maximum compressive stress.

show abstract

Ore prospecting in the Iberian Pyrite Belt using seismic and potential-field data

Cited by 10 publications

References 10 publications

Heat Flow, Geotherms, Density and Lithosphere Thickness in SW of Iberia (South of Portugal)

Heat Flow, Geotherms, Density and Lithosphere Thickness in SW of Iberia (South of Portugal)

Earthquake-faulting-related deformation in soil evidenced in S-wave shallow reflection data: Field results from Portugal

Tectonic evolution of an intraplate basin: the Lower Tagus Cenozoic Basin, Portugal

Contact Info

Product

Resources

About