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| Titel |
High-temperature metamorphism during extreme thinning of the continental crust: a reappraisal of the North Pyrenean passive paleomargin |
| VerfasserIn |
C. Clerc, A. Lahfid, P. Monié, Y. Lagabrielle, C. Chopin, M. Poujol, P. Boulvais, J.-C. Ringenbach, E. Masini, M. de St Blanquat |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1869-9510
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| Digitales Dokument |
URL |
| Erschienen |
In: Solid Earth ; 6, no. 2 ; Nr. 6, no. 2 (2015-06-08), S.643-668 |
| Datensatznummer |
250115457
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| Publikation (Nr.) |
 copernicus.org/se-6-643-2015.pdf |
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| Zusammenfassung |
| An increasing number of field examples in mountain belts show that the
formation of passive margins during extreme continent thinning may occur
under conditions of high to very high thermal gradient beneath a thin cover
of syn-rift sediments. Orogenic belts resulting from the tectonic inversion
of distal margins and regions of exhumed continental mantle may exhibit
high-temperature, low-pressure (HT-LP) metamorphism and coeval
syn-extensional, ductile deformation. Recent studies have shown that the
northern flank of the Pyrenean belt, especially the North Pyrenean Zone, is
one of the best examples of such inverted hot, passive margin. In this study,
we provide a map of HT-LP metamorphism based on a data set of more than
100 peak-temperature estimates obtained using Raman spectroscopy of the
carbonaceous material (RSCM). This data set is completed by previous
PT (pressure and temperature) estimates based on mineral assemblages, and new 40Ar–39Ar
(amphibole, micas) and U–Pb (titanite) ages from metamorphic and magmatic
rocks of the North Pyrenean Zone. The implications on the geological
evolution of the Cretaceous Pyrenean paleomargins are discussed. Ages range
mainly from 110 to 90 Ma, and no westward or eastward propagation of the
metamorphism and magmatism can be clearly identified. In contrast, the new
data reveal a progressive propagation of the thermal anomaly from the base to
the surface of the continental crust. Focusing on the key localities of the
Mauléon basin, Arguenos–Moncaup, Lherz, Boucheville and the Bas-Agly, we
analyze the thermal conditions prevailing during the Cretaceous crustal
thinning. The results are synthetized into a series of three regional
thematic maps and into two detailed maps of the Arguenos–Moncaup and Lherz
areas. The results indicate a first-order control of the thermal gradient by
the intensity of crustal thinning. The highest grades of metamorphism are
intimately associated with the areas where subcontinental mantle rocks have
been unroofed or exhumed. |
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