New Seismic and Tomography Data in the Southern Part of the Harghita Mountains (Romania, Southeastern Carpathians): Connection with Recent Volcanic Activity

Abstract

The southern part of the southeastern Carpathians represents the site of the most recent volcanic eruptions of the entire Carpathian-Pannonian region. The products of these eruptions range from 42 to 10 Ka radiocarbon ages in the South Harghita Mountains (high K calc-alkaline rocks with adakite-like features), and at 1.2-0.6 Ma K-Ar ages in the Perşani Mountains (alkali basalts). They were emplaced in a post-collisional regime. Ciomadul volcano is located at the southernmost part of the NW-SE oriented Cȃlimani-Gurghiu-Harghita range crossing the inner part of the southeastern Carpathians and in the rough proximity of the Vrancea seismic zone (at ca. 60 km toward NW). Its magma generation is attributed to 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 originating from the Vrancea intermediate-depth foci, (2) the most intense heat-flow anomaly in Romania, (3) the most prominent 3 He/ 4 He anomaly measured in natural ''postvolcanic'' gas emanations, are all in favor of the hypothesis of a still existing hot local magma chamber. Data acquired during recent seismic monitoring of the Vrancea zone and its neighborhoods suggest an enhancement of the local seismicity beneath the southern edge of the South Harghita Mts., both at crustal and subcrustal levels. At the same time, recent tomography images obtained using local earthquake data correlate well with the presence of a vertically extended low-velocity zone coming from the upper mantle to the assumed magmatic chambers located in the crust. The present data, supporting the presence of an active crustal magma chamber beneath Ciomadul, allow us to consider that future volcanic activity at this volcano cannot be discarded.

Topo-Transylvania: a multidisciplinary Earth science initiative in Central Europe to tackle local and global challenges

“…Furthermore, the post volcanic activity transports significant amounts of CO 2 and other volatiles to the surface. These tectono-magmatic processes are also associated with high-intensity geothermal anomalies, micro-seismicity and teleseismic wave attenuation beneath the SE Carpathians volcanic area and the presence of a critical low-velocity crustal anomaly observed in high-resolution seismic tomography (Popa et al 2012). Since the study area is populated, the monitoring and, eventually, warning of these potential geological hazards (seismic and volcanic) are of prime importance.…”

The latest explosive eruptions of Ciomadul (Csomád) volcano, East Carpathians — A tephrostratigraphic approach for the 51–29 ka BP time interval

“…Seismic tomography data support an active crustal magma chamber at depths of 8-20 km (Popa et al, 2012). However, to assess the possibility of future volcanic activity, a detailed chronology of the last eruptions is required.…”

Origin and geodynamic relationships of the Late Miocene to Quaternary alkaline basalt volcanism in the Pannonian basin, eastern–central Europe

“…The eruptive centres appear to be structurally controlled and show a rough NE-SW 190 trending alignment. Popa et al (2012) recorded subcrustal seismicity beneath the Perşani area 191 and, using seismic tomography modelling, suggested that a low-velocity anomaly could be 192 inferred at the crust-mantle boundary. The youngest basalt volcano (Putikov vŕšok; Šimon and 193 Halouzka, 1996) of the CPR is located near Banska Štiavnica upon the Late Pleistocene 194 terrace of the river Hron.…”