Geophysical Investigation of the Pb–Zn Deposit of Lontzen–Poppelsberg, Belgium

Abstract

The drillhole information from the Lontzen-Poppelsberg site has demonstrated three orebodies and has allowed the estimation of the extension of the lodes, their dip, and the location at the ground surface. The localisation of the lodes makes them excellent targets for further exploration with geophysics. This deposit is classified as a Mississippi Valley Type (MVT) deposit. It consists mainly of Pb-Zn-Fe sulphides that display contrasting values in resistivity, chargeability, density, and magnetic susceptibility, with regards to the sedimentary host rocks. The dipole-dipole direct current (DC) resistivity and induce polarization (IP) profiles have been collected and inverted to successfully delineate the Pb-Zn mineralization and the geological structures. Short-spacing EM34 electromagnetic conductivity data were collected mainly on the top of Poppelsberg East lode and have revealed a conductive body matching with the geologically modelled mineralization. Gravity profiles have been carried out perpendicularly to the lode orientation; they show a strong structural anomaly. High resolution ground magnetic data were collected over the study area, but they showed no anomaly over the ore deposits. The geophysical inversion results are complementary to the model based on drill information, and allow us to refine the delineation of the mineralization. The identification of the geophysical signatures of this deposit permits targeting new possible mineralization in the area.

Induced Polarization as a Proxy for CO2-Rich Groundwater Detection—Evidences from the Ardennes, South-East of Belgium

“…Interpretation [70] Pb-Zn deposit Sulphides (galena, sphalerite, pyrite and marcasite) [26] manganese deposits manganese deposits (pyrite, chalcopyrite),Fe oxides [71] Gold exploration Disseminated sulphides (pyrite, chalcopyrite),iron oxides [34] Water exploration Sand with heavy minerals [72] Detecting cracks in clay rocks 13% Pyrite in calcite rock [73] Detection of ore bodies [74] Metalliferrous veins exploration Presence of Barite and Galena [75] Plutonic rock mineral exploration Sulphure mineralizations [76] Plutonic rock mineral exploration Ore deposits [77] Galena exploration Pyrite, chalcopyrite, galena [35] Volcanic geothermal area Pyrite, iron oxides [78] Case study alluvial fans High clay content [47] Hydrocarbon contamination Clayey silt [34] Water exploration Weathered rock leaching clay minerals [79] Slope study Clay [72] Detecting cracks in clay rocks Clay rocks [80] Landfill characterization Clayey till [52] Mapping of lithotypes Clay till [81] Landfill characterization Waste, plastic and metal [82] Landfill characterization Waste, soil with leachate [80] Landfill characterization Waste and leachate [83] Landfill characterization Waste Figure 12a illustrates the difficulty of interpreting normalized chargeability data when no in-situ information is available. Except for the group Landfill that is well distinguished from the others and could possibly be discriminated based only on the normalized chargeability values, all the other groups are mixed together with values approximately in the range [0.01-1] mS/m.…”

Some Experiences of Resistivity and Induced Polarization Methods on the Exploration of Sulfide: A Review

“…The effectiveness of detecting sulfide deposits depends on the evolution of their hosting with adequate contrast in their physical properties between the base metals and their host rocks. Resistivity appears to be negatively correlated with porosity, Basalts indicate high resistivity and low IP along the resistivity, volcanic tuff areas are predominated by high resistivity values (Tavakoli et al, 2016b;Komori et al, 2017;Evrard et al, 2018) etc. The resistivity variation of various host rocks and sulfide minerals is summarized in Table 3.…”

“…expects to much contrast and detectable (Meju, 2002;Airo, 2015), because of their resistivity variations: Shale and clays present low values followed by sandstones with intermediate values, while coal and limestone beds have high values (Lau, 2000). Generally, sulfide in sedimentary hosts indicates low resistivity values with a strong correlation between the low resistivity and high chargeability areas for most of sedimentary host (Côrtes et al, 2016;Evrard et al, 2018). Massive sulfide surveyed around the submarine area usually shows low resistivity values lower than the seawater value (Goto et al, 2013;Komori et al, 2017;Ishizu et al, 2019).…”

“…Pyrrhotite is highly conducive and can significantly influence a sulfide body's general electrical conductivity signature (Roach & Fitzpatrick, 2003). Pyrite and chalcopyrite also give potentials higher polarized (too conductive) state than galena (Wells, 1914;Roach & Fitzpatrick, 2003), but sphalerite is generally insultator with less conductivity and lower IP signatures than other sulfide minerals (Komori et al, 2017;Evrard et al, 2018). It can be conducive when associated with other conducive/chargeable sulfide minerals such as pyrite and pyrrhotite, even in small quantities (Roach & Fitzpatrick, 2003;Evrard et al, 2018).…”

“…It can detect subsurface sulfide mineral distribution by studying the nature of the flow of electricity in the earth, for being uniquely able to see a large range of magnitudes which can vary up to 20 orders (Morgan, 2012). This method can delineate the various sources of mineralization according to their types (Evrard et al, 2018). The resistivity method is used to map spatial variations in subsurface electrical conductivity, while the induced polarization (IP) method is used to map changes in chargeability.…”