Interpretation of magnetic anomalies in the volcanic area of northeastern Spain

doi:10.1016/0040-1951(91)90257-S

Tectonophysics

Volume 192, Issues 1–2, 10 June 1991, Pages 201-210

https://doi.org/10.1016/0040-1951(91)90257-S Get rights and content

Abstract

Data from an aeromagnetic survey carried out in northeastern Spain are used for the interpretation of magnetic anomalies in an area of Neogene and Quaternary volcanism. Two, two-and-a-half and three dimensional models lead to the hypothesis that a larger area than that visible at the surface is affected by magmatic activity. In particular in the western part of the study a significant amount of basaltic rock seems to be located between the Paleozoic basement and about 2000–2500 m of Tertiary molasse sediments. Further east, basaltic rocks do not seem to be restricted to the areas where they outcrop but could have also filled extensional fault planes active during the Neogene without having reached the surface.

References (13)

P. Anadón et al.
Evolución tectonoestratigráfica de los Catalánides
Acta Geol. Hisp.
(1979)
V. Araña et al.
El volcanismo neógeno-cuaternario de Catalunya: Caracteres estructurales, petrológicos y geodinámicos
Acta Geol. Hisp.
(1983)
V. Baranov
A new method for interpretation of aeromagnetic maps: Pseudo-gravimetric anomalies
Geophysics
(1957)
M. Fernàndez et al.
Thermometry and hydrogeochemistry of the southern border of the South Pyrenean foreland basin
R.R. Hartman et al.
A system for rapid digital aeromagnetic interpretation
Geophysics
(1971)
R.G. Henderson
A comprehensive system of automatic computation in magnetic and gravimetry interpretation
Geophysics
(1960)

There are more references available in the full text version of this article.

Cited by (5)

Melting and metasomatism in the lithospheric mantle of NE Spain: Geochemical and SrNd isotopic characteristics
2014, Chemical Geology
Citation Excerpt :
Moreover, seismic and electrical data indicate that outcropping volcanic rocks are less than 140 m thick, with a likely Eocene substratum (Gallart et al., 1991). However, magnetic anomalies indicate that a larger volume than that exposed could have been affected by the injection of basaltic sheets and dykes (Zeyen et al., 1991). Although seismic profiles provide no evidence for the existence of magmatic bodies in the upper 5 km of the crust, the xenoliths of group II are equilibrated at ≤ 10 kbar pressure (Neumann et al., 1999), which would indicate the existence of magma bodies at the boundary crust–mantle.
The study of major and trace element compositions of whole rocks and minerals, along with SrNd isotopes on separated clinopyroxene crystals, from mantle xenoliths in Neogene–Quaternary basaltic rocks, serves to evaluate the processes which have affected the subcontinental lithospheric mantle in the Catalan Volcanic Zone of NE Spain, and to compare it to other mantle domains in Europe. These xenoliths are mainly anhydrous spinel lherzolites and harzburgites, with rare olivine websterites. Concentrations of Al₂O₃, CaO, TiO₂ and mildly incompatible trace elements decrease gradually from lherzolites to harzburgites. Light rare earth elements (LREE) and other incompatible trace elements display scatter vs. depletion indexes and usually increase from depleted lherzolites to much enriched harzburgites, indicating that metasomatism affected mainly the latter. Clinopyroxene rare earth element (REE) patterns show slight LREE depletion in most lherzolites and LREE–middle rare earth element (MREE) enrichment in harzburgites. The exceptions are a few clinopyroxene patterns from lherzolites with significant LREE–MREE depletion or LREE enrichment and u-shapes. The SrNd isotopic compositions of clinopyroxene also show a gradual variation from depleted MORB mantle (DMM) lherzolites to very enriched mantle (EM) harzburgites (⁸⁷Sr/⁸⁶Sr: 0.702486–0.709772; ¹⁴³Nd/¹⁴⁴Nd: 0.513359–0.512411). Most of these compositions match those for off-craton xenoliths. They are also similar to compositions observed in xenoliths of anhydrous spinel lherzolites and harzburgites from the neigbouring subcontinental lithospheric mantle of SE Spain and the southern part of the Massif Central, France. Fractional melting estimates from a Primitive Mantle source indicate that melt extraction was under 12% and 26% for lherzolites and harzburgites respectively. Melting took place in the spinel lherzolite field except for a few lherzolites that may have started to melt in the presence of garnet and continued in the spinel field. The formation of DMM lherzolites as refertilisation products, via percolation and reaction of N-MORB type basalts with refractory and ancient isotopically enriched harzburgites, cannot be ruled out. However, there is no definitive compositional evidence of such a process. It is suggested that harzburgites would have undergone multi-stage metasomatism. An earlier episode would have been caused by subduction-related hydrous fluids or melts related to the Variscan orogeny or an earlier orogenic episode. This is deduced from the time integrated low ¹⁴³Nd/¹⁴⁴Nd and very enriched ⁸⁷Sr/⁸⁶Sr values of harzburgite clinopyroxene. A later metasomatic episode is mainly cryptic and would have been related to the percolation of alkaline silicate melts and carbonatite derivatives. It would have affected lherzolites and especially harzburgites, causing opposite isotopic trends in the former compared to the latter. The SrNd isotopic compositions of the metasomatic agents would be close to that of a websterite xenolith. The age of this second metasomatism is also uncertain, since magmatic alkaline episodes have been registered since the Permo-Triassic periods.
Geochemistry of the Quaternary alkali basalts of Garrotxa (NE Volcanic Province, Spain): A case of double enrichment of the mantle lithosphere
2000, Journal of Volcanology and Geothermal Research
Citation Excerpt :
The NEVP developed in a series of extensional basins and minor graben-type structures hosting intraplate alkaline basaltic volcanism with close affinities to the analogous Tertiary/Quaternary intraplate magmatism of the neighboring volcanic provinces of Calatrava, Central Spain (López-Ruiz et al., 1993; Cebriá and López-Ruiz, 1995) and Massif Central, France (Chauvel and Jahn, 1984; Downes, 1984; Briot et al., 1991; Wilson and Downes, 1991; Wilson et al., 1995a), as well as the Volcanic Provinces of Germany (Mertes and Schmincke, 1985; Wörner et al., 1986; Wilson and Downes, 1991; Wedepohl et al., 1994; Hegner et al., 1995; Wilson et al., 1995b; Jung and Masberg, 1998), thus linking this volcanism to the European Cenozoic extension-related magmatism. The lavas of the NEVP have previously been studied from both the petrologic and geochemical point of view (mainly Araña et al., 1983; López-Ruiz and Rodrı́guez-Badiola, 1985) as well as from the geotectonic one (Araña et al., 1983; Zeyen et al., 1991; Martı́ et al., 1992). Although several geodynamic hypotheses have been suggested for the volcanism of the NEVP, the previously available models for the geochemical evolution of the region were insufficient and therefore the proposed geodynamic/geochemical models could not satisfactorily integrate the geological, structural, and geochemical data within a global tectonomagmatic scheme.
The area of Garrotxa (also known as the Olot area) represents the most recent (700,000–11,500 y) and better preserved area of magmatic activity in the NE Volcanic Province of Spain (NEVP). This region comprises a suite of intracontinental leucite basanites, nepheline basanites and alkali olivine basalts, which in most cases represent primary or nearly primary liquids. The geochemical characteristics of these lavas are very similar to the analogous petrologic types of other Cenozoic volcanics of Europe, which are intermediate between HIMU, DM and EM1.
Quantitative trace element modeling, suggests derivation from an enriched mantle source by degrees of melting that progressively increased from the leucite basanites (∼4%) to the olivine basalts (∼16%). However, the relatively more variable Sr–Nd–Pb isotope signature of the magmas suggests the participation of at least two distinct components in the mantle source: (1) a sublithospheric one with a geochemical signature similar to the magmas of Calatrava (Central Spain) and other basalts of Europe; and (2) an enriched lithospheric component with a K-bearing phase present. The geochemical model proposed here involves the generation of a hybrid mantle lithosphere source produced by the infiltration of the sublithospheric liquids into enriched domains of the mantle lithosphere, shortly before the melting event that generated the Garrotxa lavas.
The available geological data suggest that the first enrichment event of the mantle lithosphere under the NEVP could be the result of Late Variscan mantle upwelling triggered by the extensional collapse of the Variscan orogen during the Permo-Carboniferous. By Jurassic/Cretaceous time, large-scale NNE-directed sublithospheric mantle channeling of thermally and chemically anomalous plume material was placed under the Iberian Peninsula and Central Europe. However, the geodynamic conditions in the NEVP did not favor magmatism, which could not take place until the Cenozoic after extension started. This favored the second enrichment event of the mantle lithosphere by entrainment and storage of liquids generated in the sublithospheric plume material. After a relatively short period of time, as extension progressed, it triggered melting in the enriched portions of the mantle lithosphere during the Quaternary, generating the Garrotxa volcanism.
Space-time evolution of monogenetic volcanism in the mafic Garrotxa Volcanic Field (NE Iberian Peninsula)
2013, Bulletin of Volcanology
Thermal and redox state of the subcontinental lithospheric mantle of NE Spain from thermobarometric data on mantle xenoliths
2011, International Journal of Earth Sciences
Origin and implications of mafic xenoliths associated with Cenozoic extension-related volcanism in the València Trough, NE Spain
1999, Mineralogy and Petrology

^∗: Now at: Geophysics Institute, University of Karlsruhe, Hertzstrasse 16, Bau 42, 7500 Karlsruhe 21, FRG.

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Interpretation of magnetic anomalies in the volcanic area of northeastern Spain

Abstract

Evolución tectonoestratigráfica de los Catalánides

Acta Geol. Hisp.

El volcanismo neógeno-cuaternario de Catalunya: Caracteres estructurales, petrológicos y geodinámicos

Acta Geol. Hisp.

A new method for interpretation of aeromagnetic maps: Pseudo-gravimetric anomalies

Geophysics

Thermometry and hydrogeochemistry of the southern border of the South Pyrenean foreland basin

A system for rapid digital aeromagnetic interpretation

Geophysics

A comprehensive system of automatic computation in magnetic and gravimetry interpretation

Geophysics