Imaging the Kristineberg mining area with two perpendicular magnetotelluric profiles in the Skellefte Ore District, northern Sweden

Abstract

A B S T R A C TNew magnetotelluric (MT) data from two perpendicular profiles in the Kristineberg area, northern Sweden, were analysed and modelled. In the Skellefte Ore District, the Kristineberg volcanic hosted massive sulphide (VHMS) deposit mine is one of the largest and deepest (1250 m). Seventeen broadband magnetotelluric stations were installed along two existing seismic reflection lines. The profiles were 6 and 12 km long with 500 m and 1 km site spacing, respectively. The obtained MT transfer functions in the period range of 0.0015-200 s are of fairly good quality. Detailed strike and dimensionality analysis reveal consistent but period dependent, strike directions, indicating a change in the geoelectrical strike with depth. From the two-dimensional inversion of the determinant of the impedance tensor, two stable conductivity models with good data fit were obtained. The addition of seismic reflection information from the co-located survey, improved the data fit of one of them. Extensive sensitivity analyses helped to delineate the well resolved regions of the models and to determine the position of pronounced boundaries. The results are in good agreement with previous studies, especially regarding the presence of a deep conductor interpreted as a structural basement to the district. They also reveal with more detail the configuration of the main geological units of the Skellefte Ore District, especially of the ore bearing volcanic rocks and the embedded alteration zones.

Two‐dimensional magnetotelluric inversion using reflection seismic data as constraints and application in the COSC project

“…In simple tear-zone inversions, smoothness constraints are removed across identified borders. Tear-zone inversions of EM or ERT data with seismic or GPR constraints have been successfully applied [Doetsch et al, 2012;Favetto et al, 2007;Garcia Juanatey et al, 2013;Muñoz et al, 2010]. However, untrustworthy structural borders can introduce significant artefacts into EM or ERT inversion models and may prevent inversions from converging.…”

An integrated feasibility study using passive geophysical methods for the investigation of the Gerolekas bauxite deposits site, Greece

“…Gravity and magnetotelluric methods are traditionally applied to a great variety of different exploration surveys, including hydrocarbon, geothermal, groundwater and mining investigations (Abdelzaher et al ., 2012; De los Angeles Garcia Juanatey et al , 2013; 2016; Nabighian et al ., 2005; Chen et al ., 2015; Yehuwalashet and Malehmir 2018; Maxime et al ., 2018). The reliability and the effectiveness of both methods are heavily dependent on the correct implementation and parameterization of the entire analysis in relation to the acquisition of data and the processing steps, as well as on the use of prior information in the process of interpretation.…”