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| Titel |
Evolution of the lithosphere-asthenosphere system in the Carpathian-Pannonian region following the Miocene extension: as viewed in petrology, geochemistry, deformation pattern of mantle xenoliths and geophysical observations |
| VerfasserIn |
István Kovács, György Falus, Csaba Szabó, Zsanett Pintér, Endre Hegedűs, Judith Mihály, Csaba Németh, Nóra Liptai, Levente Patkó, Andrea Tommasi, Fabrice Barou, Zoltán Zajacz, Martina Tribus, Jürgen Konzett, Roland Stalder |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250081450
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| Zusammenfassung |
| Detailed geochemical and deformation analysis of numerous of mantle xenoliths
from the Carpathian-Pannonian region revealed that the present lithosphere, which
suffered significant thinning in the Miocene, may be divided into two major layers
based on the equilibrium temperatures as indicators for the depth of origin. The
shallower layer, from the MOHO to ~40 km depth, is characterized mostly by fine
grained, equigranular to porphyroclastic xenoliths, generally displays an ’axial
[010]’ deformation pattern typical for transpressional deformation regime. Mineral
constituents from this shallower layer show high Mg#, low H2O content in nominally
anhydrous minerals (NAMs) and depleted in basaltic major elements implying that
this layer may have undergone considerable depletion. Trace element patterns,
however, show enrichment most probably due to subsequent metasomatic enrichment
episodes.
The deeper layer is below ~40 km and above the present lithosphere-asthenosphere
boundary. The xenoliths show mainly coarse grained, protogranular texture with ’A-type’
deformation pattern typical for asthenospheric flow. Minerals usually have lower
Mg# and richer in basaltic major elements. The NAMs from this layer show higher
H2O content than those in the shallow layer. Trace element patterns, on the other
hand, do not refer to later refertilization episodes by showing dominantly depleted
pattern.
There is also a special group of tabular equigranular xenoliths, which may represent a
domain separating these shallower and deeper layers of the present day lithosphere. This
group shows geochemical and deformation properties resembling more the shallower layer,
however, the H2O content of NAMs is the highest among all studied samples. Xenoliths,
nevertheless, displaying transitional character among these major groups also occur
indicating the complex history of the upper mantle.
We suggest that the deeper, more H2O rich and less-depleted layer of the present day
lithosphere is a juvenile one, which may have added to the lithosphere following the Miocene
extension (~10 Ma) in the thermal relaxation stage. The shallower layer, in contrast, may
have undergone several episodes of depletion, deformation and refertilization prior to and
during the Miocene extension.
This layering may also be seen as seismic reflectors at ~40 km depth in the present
lithospheric mantle beneath the region, and, in addition, the anomalous seismic
anisotropy pattern beneath the CPR may also be explained by the deeper, juvenile layer. |
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