Paper Number: 1321

Paper Number: 1321 Integrated gravity and magnetics as a tool for investigating the Neogene- Quaternary volcanism of East Carpathians Besutiu, L.1, Zlagnean, L.1, Atanasiu, L.1 and Pomeran, M.1 1 Institute of Geodynamics of the Romanian Academy, Bucharest, Romania, [email protected] ___________________________________________________________________________ The East Carpathians Neogene-Quaternary volcanism (ECV) occurs in the inner part, mostly parallel to the orogene catena. Several attempts have been made to explain its genesis and peculiarities. Recently, large-scale gravity and ground geomagnetic surveys have been conducted over the ECV and neighbouring zone in the frame of INSTEC project. For some confined perimeters, investigations were performed at a higher resolution in order to help solving more intricate problems. In an area largely covered by tephra and/or sedimentary deposits, geophysics were mainly intended to outline hidden or partly cropping out volcanic forms, and to help clarify structural relationships among them, or between them and the neighbouring geological units. The paper aims at presenting some preliminary results Based on the acquired data, consistent images of the gravity and geomagnetic field have been obtained. To enhance the signal/noise ratio, data were further processed by using various filtering techniques. For example, both gravity and geomagnetic anomalies were upward transferred to planar surfaces above the topography for mitigating relief effects, and higher order derivatives have been computed to better outline the contour of the sources. To avoid distortions in positioning, the geomagnetic anomalies were reduced to the pole, and apparent susceptibility maps were constructed. Power spectra of the geomagnetic field were determined and analysed for various types of volcanic manifestations. Pseudo- gravity anomalies were inferred from the geomagnetic data, and results were Prundu Burgaului 2 compared to the Bouguer images. In-depth 3 development of volcanic structures was 1 0 km 10 km 20 km studied by using joint inversion and forward 4 6 5 modelling of the gravity and geomagnetic data under the constraints of the rock 7 Deda Stanceni physical parameters provided by the lab Toplita 0.60 nT/m 8 works. Integrated interpretation of the 0.55 nT/m 9 0.50 nT/m potential fields along with additional data 10 0.45 nT/m allowed for more documented Reghin Ghurghiu 0.40 nT/m 11 considerations on several aspects such as: 12 Gheorgheni 0.35 nT/m 0.30 nT/m (i) location of the main volcanoes along 0.25 nT/m NW-SE trending fault system that seem to 0.20 nT/m Sovata 13 15 belong to the SE extent of Trans-European 16 0.15 nT/m 14 17 0.10 nT/m Suture Zone (Fig. 1), (ii) the progressive 18 0.05 nT/m lowering of geomagnetic energy from north to south, and (iii) more accurate estimates 19 on the ratio between the volume of lava Miercurea Ciuc Vlahita 20 flows and tephra deposits. Odorheiu Secuiesc CONVENTIONAL SIGNS 21 12 volcanic edifices 22 volcanic core 23 caldera 24 neck Baraolt setlement Rupea 25 main fault system secondary faults 26 Acknowledgement. The research has been funded through a CNCS – UEFISCDI grant, project ID PN-II-ID- PCE-2012-4-0137. Figure 1: Imprints of ECV structures in the horizontal .

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