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| Titel |
Petrology and geochemistry of eclogites from the Kechros Metamorphic Complex in eastern Rhodope (NE Greece) |
| VerfasserIn |
Evripides Mposkos, Ioannis Baziotis, Paul Asimow |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250043115
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| Zusammenfassung |
| The Rhodope Metamorphic Province (RMP) is one of the major tectonic units in northern
Greece. It consists of different tectonometamorphic complexes involved in the Alpine
collisional history between the Eurasian and African plates. In eastern Rhodope a Jurassic
UHP metamorphism is documented in the uppermost Kimi Complex by the presence of
microdiamond inclusions in garnets from pelitic gneisses (Mposkos and Kostopoulos 2001).
Partially or completely amphibolitized eclogites are common recording P-T conditions >1.8
GPa and 7500C for the eclogitic stage and 1.5 GPa and 8200C for an early stage of
exhumation (Bauer et al. 2007).
In the underlying Kechros Complex lenses of kyanite eclogites in orthogneisses with
Permian ages of their gabbroic protoliths and of common eclogites within metapelites
associated with serpentinized peridotites occur.
The mineral assemblage of the kyanite eclogites is
Grt+Omp(Jd35-55)+Ky+sodic-Tr+Hbl+Zo/Czo+Phg+Qtz+Rt. Garnet shows growth
zoning with core composition Grs0.19Prp0.15Alm0.63Sps0.03 and rim composition
Grs0.20Prp0.27Alm0.52Sps0.01. Matrix omphacite is in textural equilibrium with kyanite, but
commonly it is replaced by Ca-amphibole. A decrease in jadeite component from the core to
the rim indicates a re-equilibration tendency during exhumation. Temperatures of 550-6000C
and minimum pressure of 1.5 GPa are obtained with Grt-Cpx geothermometry and the jadeite
component (Jd55) in omphacite. However, the coexistence of matrix omphacite with
kyanite constrains the minimum pressure to 2.1 GPa assuming H2O activity equal to
unity.
In the common eclogites the HP mineral assemblage is Grt+Omp+Czo+Gln+Ca-Amph.
Glaucophane is present only as inclusions in garnet. In retrogressed samples Ca-amphibole
replaces garnet and omphacite. It shows compositional zoning with increasing Al2O3 content
from 5.0 wt% in the core up to 20.0 wt% in the rim. In the eclogites subjected to extensive
retrogression, margarite associated with zoisite and albite/oligoclase (An22-28) is formed
during decompression, and with further decompression anorthite-rich plagioclase
(An75-85) is formed replacing margarite+zoisite, indicating isothermal decompression
from the maximum pressure down to 0.5 GPa. Isothermal decompression is also
documented from the mineral assemblage in associated metapelites (Mposkos,
1989).
Two protolith groups are distinguished with geochemical criteria: i) a low-Fe-Ti (LFT)
and ii) a high-Fe-Ti (HFT) group. The LFT eclogites (kyanite eclogites) have low TiO2
content ( |
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