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| Titel |
Geochronology and magma sources of Elbrus volcano (Greater Caucasus, Russia) |
| VerfasserIn |
Vladimir Lebedev |
| 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 |
250035359
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| Zusammenfassung |
| Elbrus volcano (5642m), the largest Quaternary volcano in the European part of the Russia, is
situated within the central part of Greater Caucasus mountain system at the watershed of
Black and Caspian seas. Complex isotope-geochronological studies showed that the
Elbrus volcano experienced long (approximately 200-250 thousands years) discrete
evolution, with protracted periods of igneous quiescence (approximately 50 ka) between
large-scale eruptions. The volcanic activity of Elbrus is subdivided into three phases:
Middle–Neopleistocene (225–170 ka), Late Neopleistocene (110–70 ka), and Late
Neopleistocene–Holocene (less than 35 ka). No eruptions presumably occurred during
“quiescence” periods, while the volcano was dormant or revealed only insignificant explosive
eruptions and postmagmatic activity.
Volcanic rocks of the Elbrus volcano are represented by biotite-hypersthene-plagioclase
calc-alcaline dacites (65.2-70.4% SiO2, and 6.4–7.9% K2O+Na2O at 2.7–3.9%
K2O).
Petrogeochemical and isotope-geochemical signatures of Elbrus dacitic lavas
(87Sr/86Sr – 0.70535-0.70636, Eps(Nd) from +0.8 to -2.3, 206Pb/204Pb - 18.631-18.671,
207Pb/204Pb – 15.649-15.660, and 208Pb/204Pb = 38.811-38.847) point to their
mantle–crustal origin. It was found that hybrid parental magmas of the volcano
were formed due to mixing and/or contamination of deep-seated mantle melts by
Paleozoic upper crustal material of the Greater Caucasus. The temporal evolution of
isotope characteristics for lavas of Elbrus volcano is well described by a Sr–Nd
mixing hyperbole between mantle source of “Common”-type and estimated average
composition of the Paleozoic upper crust of the Greater Caucasus. It was shown that, with
time, the proportions of mantle material in the parental magmas of Elbrus gently
increased: from ~60% at the Middle–Neopleistocene phase of activity to ~80% at the
Late Neopleistocene–Holocene phase, which indicates an increase of the activity
of deep-seated source at decreasing input of crustal melts or contamination with
time.
Unraveled evolution of the volcano with discrete eruption events, lacking signs of
cessation of the Late Neopleistocene–Holocene phase, increasing contribution of deep-seated
mantle source in the genesis of Elbrus lavas with time as deduced from isotope–geochemical
data, as well as numerous geophysical and geological evidence including presence of
fumaroles in the summit part and thermal springs along the periphery of volcano indicate that
Elbrus is a potentially active volcano and its eruptions may be resumed. One of possible
scenarios for evolution of the volcano, if its eruptive activity were to continue, suggests the
formation of large collapse caldera and catastrophic decomposition of volcanic edifice with
large-scale pyroclastic ejection and melting of glaciers at the summit part of volcano. |
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