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| Titel |
Garnet Lherzolite and Garnet-spinel mylonite in the Ronda Peridotite: Vestiges of Oligocene Back-arc mantle lithospheric extension in the Western Mediterranean |
| VerfasserIn |
Carlos J. Garrido, Frédéric Gueydan, Guillermo Booth-Rea, Jacques Précigout, Károly Hidas, José Alberto Padrón-Navarta, Claudio Marchesi |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048061
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| Zusammenfassung |
| Uplift and exhumation of vast exposures of diamond facies, subcontinental mantle
peridotite in the Western Mediterranean arc are attributed to tectonic scenarios
including pure extension, transpression or subduction followed by delamination- or
roll-back- driven stretching. In the Ronda peridotite (S Spain) the strong overprint of
low pressure assemblages has precluded accurate determination of the P and T
conditions for the onset of exhumation that formed the spinel tectonite and garnet-spinel
mylonite domain in this massif. Here we report unequivocal petrographic evidence
for the existence of prekinematic, coarse-grained garnet lherzolite assemblages
from the garnet-spinel mylonite domain of the Ronda peridotite. Application of
well-calibrated geothermobarometers yields prekinematic minimum equilibration
conditions at 2.4–2.7 GPa and 1020–1100 Ë C, demonstrating that the Ronda peridotite
equilibrated at ca. 85 km before shearing. We also show the existence of synkinematic
garnet and spinel assemblages that overprinted garnet lherzolite assemblages at
800–900 Ë C and 1.95–2.00 GPa. The decompressive cooling path and high-pressure
recorded by garnet-spinel mylonites rule out they were formed by near-isobaric
cooling above a subduction-collision wedge or during (or after) the emplacement of
the peridotite massif into the crust. Ronda garnet-spinel mylonites represent the
vestiges of subcontinental mantle ductile shear zones formed at early stages of
lithosphere extension during back-arc extension in the Western Mediterranean.
South-to-westward retreat of the African slab during the Oligocene-Early Miocene accounts
for intense back-arc lithosphere extension and development of Ronda extensional
shear zone, coeval with extreme thinning of the Alborán domain overlying crust. |
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