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3D TEM and Gravity Modeling over the Lombador Deposit, Neves-Corvo, Portugal
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, EAGE 2020 Annual Conference & Exhibition Online, Dec 2020, Volume 2020, p.1 - 5
Abstract
Summary
The 150 Mt Lombador massive sulphide deposit is one of the seven known deposits of the Neves-Corvo mine, in southern Portugal. The deposit dips approximately 45º to the NE and is open down dip, with current exploitation reaching 1 km depth. To investigate the possible continuation of the deposit down dip, a 1D constrained inversion of time-domain electromagnetic (TEM) ground loop data was conducted, followed by 3D EM forward modeling and a constrained 3D gravimetric inversion over the same area. To perform the EM and gravity modelling/inversion, a 3D geologic model was built using a density database comprised of approximately 300 drill-holes and some surface measurements from resistivity surveys. The EM modeling shows that the black pyritic shales are a regional conductive layer which extend to around 1.6 km depth below surface in the Lombador area. This layer is underlain by massive sulphides. The densities of black pyritic shales average 2.83 g/cm3, whereas stockwork and massive sulphide reach 3.2 g/cm3 and 4.6 g/cm3, respectively. The 3D constrained gravity inversion results support the hypothesis that a dense unit is located in the down-dip direction of the Lombador deposit which may have potential to contain stockwork or massive sulphide mineralization.
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