Barnscheid, Kim Carolin and Hölz, Sebastian (2021) Qualitative and quantitative analysis of the new marine electromagnetic “Coil2Dipole” experiment. [Poster] In: 81. Jahrestagung der Deutschen Geophysikalischen Gesellschaft (DGG). , 01.03.-05.03.2021, Kiel (online) .

Abstract

The formation of marine massive sulfides is connected to offshore hydrothermal circulation, where minerals from the underlying crust are mobilized and transported towards the seafloor. These sulfides have a high electrical conductivity, which can be detected by electromagnetic systems. To study potential occurrences of massive sulfides at the Grimsey Vent Field, which is located to the North of Iceland, two research cruises were in 2018 and 2019. Even though the Grimsey Vent Field is hydrothermally active, previous geoscientific studies were not able to detect these massive sulfides in the seafloor.In order to detect potential occurrences of massive sulfides, several electromagnetic (EM) experiments were done. One of those experiments is the ”Coil2Dipole” experiment, in which the mobile MARTEMIS transmitter system (developed at GEOMAR), which uses a coil antenna, is used to generate a time varying magnetic field. After turning off the electrical current in the transmitter, the induced EM fields are measured with stationary Ocean Bottom EM-receiver (OBEM-receiver) on the seafloor. Through the receivers placed on the seafloor the signal is detectable up to distances of 250m, which yield depth of investigation of about 120m. A ranging system allows for the precise distance measurements between MARTEMIS and OBEM-receivers. This is important for the correct interpretation of acquired data, since the offset has great influence on detected signal.In previous studies (Safipour et al., 2017, Geophysics; Safipour et al., 2018, Geophysical Prospecting) it was demonstrated that the “Coil2Dipole” is suitable to detect conductive targets, like massive sulfides in the seafloor. In this study we carry out a qualitative analysis in terms of 1D modelling of the data. Generally, we observed increasing resistivities with larger depthof investigation, which we attribute to the compaction of the seafloor. In the vicinity of one OBEM-receiver, which is located to the West of the active vent field, we detect a conductive layer, which indicates massive sulfides. Models of other receivers show a resistive seafloor. Finally, a parameter analysis confirms the results of the quantitative analysis.

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