SPM Discrimination in Airborne TDEM Data - A Case Study from the Maniitsoq Area, Southwestern Greenland

SPM effects, which are mainly caused by fine-grained iron particles such as maghemite and magnetite constitute a geological noise in modern airborne transient Time Domain EM (TDEM) systems. Therefore, their identification and discrimination is important when exploring for bedrock conductors associated with metallic mineralisation such as nickel and sulphides. In the transient TDEM data, they are manifested by a power law decay fit at mid-late time close to -1. In this paper, we describe other approaches for identifying and discriminating SPM anomalies observed in the transient TDEM data from Greenland, including a) innovative dual-EM receiver configuration (vertical EM gradiometer), and b) a multiple criteria pattern recognition approach, based on maximum likelihood algorithm. As a result, many SPM-related detected by airborne TDEM surveys were identified and were hence discriminated from further follow-up. Diamond drill testing in 2016 performed on selected targets that were categorized as non-SPM related, has confirmed their link to bedrock conductors and sulphide mineralization.