HR: 1400h
AN: V53A-02    [Abstracts]
TI: Variable slab and subarc mantle signatures within dying arc setting-clues from the volcanology and geochemistry of Quaternary volcanic rocks from Armenia.
AU: * Savov, I P
EM: savov@dtm.ciw.edu
AF: Carnegie Institution of Washington , Department of Terrestrial Magnetism 5241 Broad Branch Road, NW, Washington, DC 20015, United States
AU: Luhr, J
EM: luhrj@si.edu
AF: Smithsonian Institution, National Museum of Natural History-Global Volcanism Program, Washington, DC 20560, United States
AU: D'Antonio, M
EM: masdanto@unina.it
AF: University Federico II Napoli , L.go S. Marcellino 10, Naples, 80138, Italy
AU: Connor, C
EM: cconnor@cas.usf.edu
AF: University of South Florida, 4202 E.Fowler Ave, SCA 528, Tampa, FL 33620, United States
AU: Karakhanian, A
EM: georisk@sci.am
AF: Armenian National Academy of Sciences, Geological Institute Marshal Baghramian Ave. 24a , Yerevan, 375019, Armenia
AU: Ghukasyan, Y
EM: yughukasyan@yahoo.com
AF: Armenian National Academy of Sciences, Geological Institute Marshal Baghramian Ave. 24a , Yerevan, 375019, Armenia
AU: Djrbashian, R
EM: jrb_rub@sci.am
AF: Armenian National Academy of Sciences, Geological Institute Marshal Baghramian Ave. 24a , Yerevan, 375019, Armenia
AB: Armenian volcanoes occur within the active continental collision zone involving the Arabian and Eurasian plates. The volcanism is hosted by a chain of pull-apart basins, cumulatively forming an arc across Armenia and extending into Turkey and Iran. We collected fresh volcanic rocks from >100 volcanoes in proximity to the large calc-alkaline strato-volcano Mt.Ararat (Turkey) and the sub-alkaline shield-volcano Mt.Aragats (Armenia).The samples are trachybasalt-andesites o dacites (Aragats Volcanic Plateau) and trachybasalts to rhyolites (Arteni Volcanic Complex, Gegham Plateau and Lake Sevan regions).The major and trace element systematics of the Armenian volcanics reveal mixed arc-like and OIB-like signatures may accompany the transition from subduction to collision (Miocene-recent). Relative to N-MORB our samples show enrichments of fluid mobile elements,Th,U,LILE and LREE,and depletions of HREE and Hf, Nb, Ta and Zr.The lower 87Sr/86Sr ratios (0.7041 to 0.7051) compared to any known crustal material in the region, the regional mantle 144Nd/143Nd isotope ratios [0.5128-0.5129] and the absence of crustal xenoliths cause us to conclude that crustal assimilation did not play a significant role in the magmagenesis.We will report large mineral chemistry dataset and detailed textural observations revealing no significant mineral zoning.Based on mineral rim and groundmass chemistries and using variety of hygrothermometers, we calculated melt H2O contents ranging from 1.9 to 4.5 wt% and also elevated eruption temperatures [range= 1030- 1060°C].This calculations are in agreement with the generally anhydrous nature of the mineral assemblages [Pl+Opx+Cpx+Ol+TiMt] and with the ionprobe study of volatile contents in olivine hosted melt inclusions [H2O = 0.5-2.8 wt%; CO2 = 10-371 ppm; F= 1865-2905 ppm, S= 225-5122 ppm;Cl= 650-1013 ppm]. Although other mechanisms such as delamination and localized extension related to strike slip faulting might also contribute to magma generation we suggest that the unusual combination of anhydrous but fluid mobile element, LILE and LREE-enriched mantle source under the Armenia is due to long-lasting (Jurassic- Miocene) pre-collisional subduction modifications, followed by slab break-off and interaction with hot mantle asthenosphere [1]. Our new data confirms recent tomography scans showing heterogeneous hot mantle domain under the volcanic highlands of Armenia based on large and sharp low shear wave velocity anomaly correlated with long wavelength free-air gravity anomalies [2]. [1] Keskin, M. (2003). Magma generation by slab steepening and breakoff beneath a subduction-accretion complex: An alternative model for collision-related volcanism in Eastern Anatolia, Turkey, Geophys. Res. Lett.,30(24),8046. [2] Maggi, A. and Priestley, K. (2005). Surface waveform tomography of the Turkish-Iranian plateau, Geophys. J. Int.,160, 1068-1080.
DE: 3060 Subduction zone processes (1031, 3613, 8170, 8413)
DE: 3613 Subduction zone processes (1031, 3060, 8170, 8413)
DE: 8170 Subduction zone processes (1031, 3060, 3613, 8413)
DE: 8413 Subduction zone processes (1031, 3060, 3613, 8170)
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly