UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2011 Meeting


Section: Atmosphere and Earth Science; Environment Protection


Title:
New seismic and tomography data in the southern part of the Harghita Mountains (Romania, south-eastern Carpathians): connection with recent volcanic activity


Authors:
B. Zaharia


Affiliation:
National Institute for Earth Physics, 12 Calugareni str., Magurele, 077125, Romania,


E-mail
bzaharia@infp.ro


Keywords:
mantle seismicity, Neogene volcanism, post-collisional tectonics, asthenospheric ascent, Vrancea region


Abstract:
The southern part of the South-Eastern Carpathians represents the site of the most recent volcanic eruptions from the entire Carpathian-Pannonian region. The products of these eruptions were dated using radiocarbon method ranging 42 - 10 Ka in the Harghita Mountains, as high K calc-alkaline with adakite-like features and 0.6 Ma in Perşani Mts as alkali basalts. They are characteristic for a post-collisional regime. Ciomadul is situated in the southernmost prolongation of NW to SE oriented Călimani-Gurghiu-Harghita range crossing the inner part of the South-Eastern Carpathians. Ciomadul volcano is located in the rough proximity of the Vrancea seismic zone (a shift of about 60 km toward NW) and its magma generation is attributed to the geodynamic events closely related to the seismogenic area. A number of particular geophysical and geochemical features located in the study region including: 1) the abrupt attenuation of the seismic waves coming from the Vrancea intermediate depth foci for paths going toward to the southern edge of the Harghita Mountains, 2) the most intense heat-flux anomaly in the whole Romania, 3) the most prominent 3He/4He anomaly measured in natural gases and thermal mineral waters, are all in favor of the hypothesis of a still existing local hot magma chamber. Data acquired during recent seismicity monitoring of the Vrancea zone, benefited also from the stations installed in the interior of the Carpathian bend area suggest an enhancement of the local seismicity beneath the southern edge of the Harghita Mountains, both in the crustal and subcrustal levels. At the same time, recent tomography images obtained using local earthquake data correlate well with the presence of a vertical low-velocity material coming from the upper mantle to the assumed magmatic chambers located in the crust. The present data that favor the presence of active crustal magma chambers allow us to consider that mainly Ciomadul, but also Perşani magmatic areas should have possible future activity.