Geophysical evidence of a mantle derived intrusion in SW Iberia

Abstract

[1] 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.

Crustal structure of the SW Iberian passive margin: The westernmost remnant of the Ligurian Tethys?

“…As pointed out by Torne et al (2015), the regional gravity high that delineates the southwestern Variscan terranes of the Ossa Morena and South Portuguese zones is related to the combination of a slight thinning of the crust towards the shoreline and to the presence of a somewhat denser crust relative to the average of the Alpine Iberia (15 to 20 kg/m 3 denser). These results agree with previous seismic studies which found that the mid/lower crust was intruded by a regional high velocity/reflective body and that the base of the crust is located at about 31-32 km (e.g., Carbonell et al, 2004;Palomeras et al, 2009).…”

The Aguablanca Ni–(Cu) sulfide deposit, SW Spain: geologic and geochemical controls and the relationship with a midcrustal layered mafic complex

“…Recent seismic-reflection work has shown the existence of a 1-5-km-thick high-velocity zone at about 10 to 15 km depth throughout the Ossa Morena Zone where the large Variscan thrusts and faults are interpreted to be rooted (IRB, Iberian Reflective Body; Simancas et al 2003;Carbonell et al 2004). The more likely interpretation is that the reflector represents a large sill-like structure of mafic ultramafic rocks intruded during the Variscan times (Simancas et al 2003).…”

Modelling of the Neves Corvo Area

“…Not much after the last CGG survey, the first deep seismic reflection profile started in the Spanish part of the IPB, close to the Portuguese border (e.g. Simancas et al 2003;Carbonell et al 2004). In Portugal, useful results were obtained using seismic reflection and gravimetric modelling for shallow massive sulphides exploration, under a relatively thin Tertiary cover that occurs in the NW part of the IPB (Oliveira et al 1998;Carvalho et al 2011).…”

“…several dykes associated with late Variscan faults) and the interpretation of deeper units. Information from the Iberseis profiles (Simancas et al 2003;Carbonell et al 2004) was used for this. When all the profiles were interpreted, we checked the consistency of the interpretation with gravimetric and aeromagnetic data that covered almost all the study area.…”