Investigation of a Mid-crustal Conductor in the North Gjallar Ridge, Offshore Norway, Inferred from Magnetotelluric Data

Corseri, Romain; Senger, Kim; Maharjan, Dwarika; Pedersen, C.B.

doi:10.3997/2214-4609.201413214

Cited by 1 publication

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“…Three typical MT responses rotated along the direction of profile P3 are displayed in Figure 4. After processing using the robust multi-station processing scheme of Egbert (1997) combined with a proprietary autogrouping algorithm (Markhus et al, 2015), the 120 stations ( Figure 2) provided good quality MT signal for periods from 1 to 1500 s (Corseri et al, 2015). Subsequently, all 120 stations were used in the inversion phase.…”

Section: Mt Data Acquisition and Analysismentioning

confidence: 99%

“…In this contribution, we carried out 2D inversion of MT data along five profiles ( Figure 2), totalling ~140 km. We obtained good quality MT data from periods 2 to 1500 s, which allow for the investigation of geo-electrical features in the upper continental crust (Corseri et al, 2015). To support the 2D inversion approach and the recovery of abnormally low resistivity (< 0.8 Ω.m) at mid-crustal depths, we performed a dimensionality and electromagnetic strike analysis.…”

Section: Introductionmentioning

confidence: 99%

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Magnetotelluric evidence for massive sulphide mineralization in intruded sediments of the outer Vøring Basin, mid-Norway

Corseri

Senger²,

Selway

et al. 2017

Tectonophysics

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A highly conductive body (0.1-0.8 Ω.m) is identified at mid-crustal depth (8-13 km) in the north Gjallar Ridge from magnetotelluric (MT) data and further investigated in light of other remote-sensing geophysical data (Seismic reflection, gravity, aeromagnetic). A commercial 3D controlled-source electromagnetic survey was conducted in the Vøring Basin in 2014 and, although primarily designed for hydrocarbon exploration, good quality MT data were extracted at periods ranging from 10 0 to 10 3 s. Dimensionality analysis indicates clear 1D to 2D characteristics in the MT data. 2D inversion was carried out on four profiles (totalling ~94 km) oriented perpendicular to the electromagnetic strike and one profile along strike (~45 km), using a 1D subset of the data. All inversions converged quickly to RMS values close to unity and display a very good agreement with borehole resistivity data from well 6705/10-1 located in the survey area. A striking feature on all profiles is a highly conductive (0.1-0.8 Ω.m) body at 8-13 km depth. To explain the prominent conductive anomaly, integration of geophysical data favours the hypothesis of electrical conduction across well-connected mineral network in pre-Cretaceous sediments. Seismic interpretation suggests a link between the conductor and intruded sedimentary successions below a detachment level and associated low-angle faults. In the Vøring Basin, low magnetic signal and temperature at the conductor's depth indicate that such thick mineral deposits could display non-magnetic behaviour while occurring well below the magnetite Curie isotherm (~585°C). Natural occurrences and magnetic properties of common iron-sulphide minerals favour a geological interpretation of mid-crustal conductivity as thick pyrrhotite deposits formed in intrusion's contact metamorphic aureoles.

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Section: Mt Data Acquisition and Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%