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Petrophysical analysis of a mid-crustal reflector in the IBERSEIS profile, SW Spain
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2012 (English)In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 550, 35-46 p.Article in journal (Refereed) Published
Abstract [en]

The origin of strong crustal reflectors in vertical incidence reflection seismic data is generally attributed to either rock layering, deformation fabrics in shear zones, fluids, or igneous intrusions. The IBERSEIS normal incidence reflection and wide-angle seismic profiles in SW Spain imaged a large, high velocity, subhorizontal reflector in the middle crust (the IBERSEIS Reflective Body) whose origin has been attributed to a mafic intrusion. In order to test this hypothesis, in this paper we present laboratory measurements of Vp, Vs, and density from 17 samples of mafic igneous and metamorphic rocks, and metasediments that are thought to be equivalent to the proposed IBERSEIS Reflective Body. These measurements are then corrected to 400 degrees C at 600 MPa and used to calculate Poisson's ratio and to compare it, Vp, and Vs to values measured in situ by wide-angle data. Finally, normal incidence reflection coefficients are calculated to test if the measured lithologies could reproduce the reflectivity imaged in the vertical incidence reflection seismic data for the IBERSEIS Reflective Body. Our physical property measurements are very similar to those modeled from the wide-angle data, and our reflection coefficients are sufficiently high to cause strong mid-crustal reflectivity. Our data indicate, therefore, that previous interpretations of the IBERSEIS Reflective Body as a mafic sill are quite reasonable.

Place, publisher, year, edition, pages
2012. Vol. 550, 35-46 p.
Keyword [en]
Petrophysics, Mid-crustal reflectors, IBERSEIS, Seismic velocities
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-181941DOI: 10.1016/j.tecto.2012.05.004ISI: 000306878300003OAI: oai:DiVA.org:uu-181941DiVA: diva2:558233
Available from: 2012-10-02 Created: 2012-10-02 Last updated: 2012-10-02Bibliographically approved

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Juhlin, Christopher
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