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- Simancas, J.F., et al.
(författare)
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The seismic crustal structure of the Ossa-Morena Zone and its geological interpretation
- 2004
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Ingår i: Journal of Iberian Geology. - 1698-6180 .- 1886-7995. ; 30, s. 133-142
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Tidskriftsartikel (refereegranskat)abstract
- The IBERSEIS deep reflection seismic experiment has provided a crustal image of the Variscan orogen of southwest Iberia. A brief presentation of the entire seismic profile is given, and then the Ossa-Morena Zone (OMZ) and its boundaries are considered. The crust of the OMZ is shown to be divided into an upper crust, characterized by dominantly NE-dipping reflectivity, and a poorly reflective lower crust. The reflectivity of the upper crust has good correlation with the geological cross-section constructed from surface mapping. In the seismic image, the upper crustal geological structures are seen to merge in the middle crust. Nevertheless, the OMZ middle crust is not a mere detachment level, as it shows very unusual features: it appears as a band of strong reflectivity and irregular thickness (the Iberian Reflective Body, IRB) that we interpret as a great sill-like intrusion of basic rocks. The boundaries of the OMZ are considered sutures of the orogen, and their geometrical features, as deduced from geological mapping and the seismic image, are in accordance with the transpressional character of the Variscan collision recorded in SW Iberia. The present Moho is flat, obliterating the root of the orogen.
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| 3. |
- Carbonell, R., et al.
(författare)
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Geophysical Evidence of a Mantle Plume Derived Intrusion Complex
- 2004
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Ingår i: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 31, s. L11601-
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Deep seismic reflection data acquired as part of the SW-Iberia EUROPROBE project across the transpressional Variscan orogen sample three tectonic terranes: the South Portuguese Zone, the Ossa-Morena Zone, and the Central Iberian Zone. The seismic data reveal the existence of a mid-crustal reflective body 140 km long and of variable thickness (up to 5 km), the Iberian Reflective body. The conductivity image provided by coincident MT soundings, the amplitude characteristics of the seismics, mineralization studies related to magmatic ore deposits, and the surface geology suggest that the IRB is a mantle-derived mafic intrusion. The geophysical, geological and petrological data suggest that the IRB is most probably an Early Carboniferous (approximately at 350–340 Ma) mantle-derived intrusion possibly linked to plume activity that took place in Europe in the Carboniferous and Permian.
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| 4. |
- Simancas, J. F., et al.
(författare)
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Crustal structure of the transpressional Variscan orogen of SW Iberia : SW Iberia deep seismic reflection profile (IBERSEIS)
- 2003
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Ingår i: Tectonics. - : AGU. - 0278-7407 .- 1944-9194. ; 22, s. 1062-
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Tidskriftsartikel (refereegranskat)abstract
- IBERSEIS, a 303 km long (20 s) deep seismic reflection profile, was acquired across the Variscan belt in SW Iberian Peninsula. The acquisition parameters were designed to obtain a high-resolution crustal-scale image of this orogen. The seismic profile samples three major tectonic terranes: the South Portuguese Zone, the Ossa-Morena Zone, and the Central Iberian Zone, which were accreted in Late Paleozoic times. These terranes show a distinctive seismic signature, as do the sutures separating them. Late strike-slip movements through crustal wedges are apparent in the seismic image and have strongly modified the geometry of sutures. The upper crust appears to be decoupled from the lower crust all along the seismic line, but some deformation has been accommodated at deeper levels. A sill-like structure is imaged in the middle crust as a 1–2 s thick and 175 km long high-amplitude conspicuous reflective band. It is interpreted as a great intrusion of mafic magma in a midcrustal decollement. Taking into account surface geological data and the revealed crustal architecture, a tectonic evolution is proposed for SW Iberia which includes transpressional collision interacting during Early Carboniferous with a mantle plume. The Moho can be identified along the entire transect as subhorizontal and located at 10 to 11 s, indicating a 30–35 km average crustal thickness. Its seismic signature changes laterally, being very reflective beneath the South Portuguese Zone and the Central Iberian Zone, but discontinuous and diffuse below the Ossa Morena Zone.
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