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| Titel |
Pliocene-Quaternary Post-collisional Magmatism in the Greater Caucasus |
| VerfasserIn |
Samuel Bewick, Nigel Harris, Ian Parkinson, Sam Hammond, Shota Adamia |
| 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 |
250099057
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| Publikation (Nr.) |
 EGU/EGU2014-14800.pdf |
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| Zusammenfassung |
| Whole-rock elemental and isotopic analyses are presented for Pliocene-Quaternary volcanism
from northern Georgia. Intense magmatic activity erupted through the thickened crust
(50-60km) of the Greater Caucasus mountain belt, tens of millions of years following
continental collision between the Arabian and Eurasian plates.
Compositions range from basaltic-andesite to dacite (56-67 wt% SiO2). Enrichment of large
ion lithophile elements (LILEs) and light rare earth elements (LREEs) relative to the
high field strength elements (HFSEs) is seen in all samples. Rare earth element
patterns have small enrichments in the middle to heavy REE ((Dy/Yb)N ratios
(1.22-1.65)). Strontium (87Sr/86Sr of 0.7041-0.7049) and Pb isotope ratios suggest a
source that has been enriched relative to DMM with Pb isotopes plotting on an array
sub-parallel to, but enriched compared to the northern hemisphere reference line (Δ7/6 =
10.7-11.3).
LILE enrichment may be indicative of a source enriched by subduction related fluids.
Compositions are also similar to local crustal samples. On Pb isotope plots, samples lie on a
trend extending towards radiogenic crustal values. Trace elements and isotopes are used to
decipher the importance of these two signatures. Heavy REE data provide evidence melting
was relatively shallow ( 10wt%) indicate fractionation occurred deep in the
crust.
Further investigation will allow the sources for Greater Caucasus magmatism to be better
constrained and the petrologic evolution of the magmas to be compared with those from the
wider Arabia-Eurasia collision zone and hence integrated into a post-collisional tectonic
model for the region. |
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