Deep massive sulphide exploration using 2D and 3D geoelectrical and induced polarization data in Skellefte mining district, northern Sweden

Abstract

A B S T R A C TGeoelectrical and induced polarization data from measurements along three profiles and from one 3D survey are acquired and processed in the central Skellefte District, northern Sweden. The data were collected during two field campaigns in 2009 and 2010 in order to delineate the structures related to volcanogenic massive sulphide deposits and to model lithological contacts down to a maximum depth of 1.5 km. The 2009 data were inverted previously, and their joint interpretation with potential field data indicated several anomalous zones. The 2010 data not only provide additional information from greater depths compared with the 2009 data but also cover a larger surface area. Several high-chargeability low-resistivity zones, interpreted as possible massive sulphide mineralization and associated hydrothermal alteration, are revealed. The 3D survey data provide a detailed high-resolution image of the top ß450 m of the upper crust around the Maurliden East, North, and Central deposits. Several anomalies are interpreted as new potential prospects in the Maurliden area, which are mainly concentrated in the central conductive zone. In addition, the contact relationship between the major geological units, e.g., the contact between the Skellefte Group and the Jörn Intrusive Complex, is better understood with the help of 2010 deep-resistivity/chargeability data. The bottommost part of the Vargfors basin is imaged using the 2010 geoelectrical and induced polarization data down to ß1-km depth.

Potential Field, Geoelectrical and Reflection Seismic Investigations for Massive Sulphide Exploration in the Skellefte Mining District, Northern Sweden

“…This was the motivation for deeper geoelectrical investigation thereby the subsurface resistivity down to ca. 1.5 km depth as well as inside a 3D area was imaged (Tavakoli et al 2016). The result from new data strengthened some earlier interpretations, but also provided new insights about anomalies at greater depths (i.e., 0.5-1 km depth).…”

“…2). In contrary to the 2009 profiles for which the potential dipoles (px-py) possessed a constant spacing of 200 m from the current electrode C1, in 2010 C1 was moved between a group of fixed dipoles which were connected differently, depending on the distance of the dipole to C1 (Tavakoli et al 2016). Profile E-1 was 10 km long, covered the SW continuation of Profile II, and imaged the top 1.5 km of the upper crust.…”

“…During two field campaigns, resistivity and chargeability of the subsurface was measured along three profiles (I, II, and E-1; Tavakoli et al 2012aTavakoli et al , 2016 and inside an area in 3D (Tavakoli et al 2016). The field work was carried out using pole-dipole electrode configuration; however, each survey was designed using a specific electrode array and hence different penetration depths were acquired.…”

“…The result from new data strengthened some earlier interpretations, but also provided new insights about anomalies at greater depths (i.e., 0.5-1 km depth). On the other hand, the 3D data, although cover a very small area compared to all other geophysical results, provided valuable result about the distribution of the sulphide ore around the Maurliden deposits (Tavakoli et al 2016). Potential field data was also used to confirm, and in some cases improve the interpretation of the seismic reflection data (Tavakoli et al 2012b).…”

“…The shallow-scale and deep-scale geophysical studies are classified based on the resolution and investigation depth of each method. Shallow investigations provide a high resolution image of the subsurface down to ~ 1.5 km depth and include 2D and 3D resistivity/IP data (Tavakoli et al 2012a(Tavakoli et al , 2016 constrained with potential field data. Deep investigations include seismic reflection (Dehghannejad et al 2012a), MT (García Juanatey 2012) and potential field data (Tavakoli et al 2012b) which provide a deep image of the subsurface down to ~ 4.5 km depth.…”