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| Titel |
Subduction initiation and recycling of Alboran domain derived crustal components prior to the intra-crustal emplacement of mantle peridotites in the Westernmost Mediterranean: isotopic evidence from the Ronda peridotite |
| VerfasserIn |
María Isabel Varas-Reus, Carlos J. Garrido, Delphine Bosch, Claudio Marchesi, Antonio Acosta-Vigil, Károly Hidas, Amel Barich |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250096452
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| Publikation (Nr.) |
 EGU/EGU2014-11959.pdf |
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| Zusammenfassung |
| During Late Oligocene-Early Miocene different domains formed in the region between Iberia
and Africa in the westernmost Mediterranean, including thinned continental crust and a
Flysch Trough turbiditic deposits likely floored by oceanic crust [1]. At this time, the Ronda
peridotite likely constituted the subcontinental lithospheric mantle of the Alboran domain,
which mantle lithosphere was undergoing strong thinning and melting [2] [3] coevally with
Early Miocene extension in the overlying Alpujárride-Maláguide stacked crust [4,
5].
Intrusive Cr- rich pyroxenites in the Ronda massif records the geochemical processes
occurring in the subcontinental mantle of the Alboran domain during the Late Oligocene [6].
Recent isotopic studies of these pyroxenites indicate that their mantle source was
contaminated by a subduction component released by detrital crustal sediments [6]. This new
data is consistent with a subduction setting for the late evolution of the Alboran lithospheric
mantle just prior to its final intracrustal emplacement in the early Miocene Further detailed
structural studies of the Ronda plagioclase peridotites—related to the initial stages of ductile
emplacement of the peridotite—have led to Hidas et al. [7] to propose a geodynamic model
where folding and shearing of an attenuated mantle lithosphere occurred by backarc basin
inversion followed by failed subduction initiation that ended into the intracrustal
emplacement of peridotite into the Alboran wedge in the earliest Miocene. This hypothesis
implies that the crustal component recorded in late, Cr-rich websterite dykes might
come from underthrusted crustal rocks from the Flysch and/or Alpujárrides units
that might have been involved in the earliest stages of this subduction initiation
stage.
To investigate the origin of crustal component in the mantle source of this late magmatic
event recorded by Cr-pyroxenites, we have carried out a detail Sr-Nd-Pb-Hf isotopic study of
a variety of Betic-Rif cordillera crustal rocks that might have been potentially subducted
beneath the Alborán domain before the emplacement of Ronda peridotites. Isotopic data rules
out potential crustal sources coming from pre-early Miocene Flysch Trough sediments and
crustal rocks from the Blanca Unit currently underlying peridotite. Crustal rocks from the
Jubrique Unit overlying the Ronda peridotite are the only crustal samples that may account
for the relatively high 207Pb-208Pb/204Pb and low 206Pb/204Pb characteristic of the crustal
contaminant added to the mantle source of late Cr-pyroxenites. These data strongly
support Alboran geodynamic models that envisage slab roll-back as the tectonic
mechanism responsible for Miocene lithospheric thinning, and provides a scenario where
back-arc inversion leading to self-subduction of crustal units at the front of the Alboran
wedge.
REFERENCES
1. Durand-Delga, M., P. Rossi, P. Olivier, and D. Puglisi, Situation structurale et nature
ophiolitique de roches basiques jurassiques associées aux flyschs maghrébins du Rif (Maroc)
et de Sicile (Italie). Comptes Rendus de l’Académie des Sciences - Series IIA - Earth and
Planetary Science, 2000. 331(1): p. 29-38.
2. Lenoir, X., C. Garrido, J.L. Bodinier, J.M. Dautria, and F. Gervilla, The Recrystallization
Front of the Ronda Peridotite: Evidence for Melting and Thermal Erosion of Subcontinental
Lithospheric Mantle beneath the Alboran Basin. Journal of Petrology, 2001. 42(1): p.
141-158.
3. Garrido, C.J., F. Gueydan, G. Booth-Rea, J. Precigout, K. Hidas, J.A. Padrón-Navarta,
and C. Marchesi, Garnet lherzolite and garnet-spinel mylonite in the Ronda peridotite:
Vestiges of Oligocene backarc mantle lithospheric extension in the western Mediterranean.
Geology, 2011.
4. Balanyá, J.C., V. García-Dueñas, J.M. Azañón, and M. Sánchez-Gómez, Alternating
contractional and extensional events in the Alpujarride nappes of the Alboran Domain
(Betics, Gibraltar Arc). Tectonics, 1997. 16(2): p. 226-238.
5. Platt, J.P., M.J. Whitehouse, S.P. Kelley, A. Carter, and L. Hollick, Simultaneous
extensional exhumation across the Alboran Basin: Implications for the causes of late
orogenic extension. Geology, 2003. 31(3): p. 251-254.
6. Marchesi, C., C.J. Garrido, D. Bosch, J.-L. Bodinier, K. Hidas, J.A. Padrón-Navarta,
and F. Gervilla, A Late Oligocene Suprasubduction Setting in the Westernmost Mediterranean
Revealed by Intrusive Pyroxenite Dikes in the Ronda Peridotite (Southern Spain). The Journal
of Geology, 2012. 120(2): p. 237-247.
7. Hidas, K., G. Booth-Rea, C.J. Garrido, J.M. Martínez-Martínez, J.A. Padrón-Navarta,
Z. Konc, F. Giaconia, E. Frets, and C. Marchesi, Backarc basin inversion and subcontinental
mantle emplacement in the crust: kilometre-scale folding and shearing at the base of the
proto-Alborán lithospheric mantle (Betic Cordillera, southern Spain). Journal of the
Geological Society, 2013. 170(1): p. 47-55. |
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