Inversion modelling helps define kimberlite targets in the Northwest Territories
A filtering process refined by inversion modelling in Geosoft VOXI has given Margaret Lake Diamonds (MLD) the confidence to select 12 drill targets from more than 60 geophysical anomalies on its 50,000 acre diamond property in the Northwest Territories.
To narrow down the 67 geophysical anomalies resulting from the HeliFALCON® survey, consultants Campbell & Walker Geophysics used all the information they could gather to rank targets, including historic geophysical and geochemical results from ground surveys. Of the 67, eight were based solely on their magnetic response and eleven on previous geophysical data in the assessment files that was confirmed by the 2014 AGG survey. The remaining 48 were based on a combination of their AGG and magnetic responses.
The consultants assigned a rank of one (highest) to four (lowest) to each of the 67 anomalies based on its geophysical and geological (e.g. proximity to indicator minerals) character. None of the anomalies received the highest ranking, but there were 37 in rank 3 and one in rank 2.
After further review, the team selected five Priority A and 17 Priority B targets for inversion modeling using Geosoft VOXI. The model included the Fourier-processed tensor GED, GND and GDD components of the gravity gradiometry data and incorporated magnetics where applicable.
They viewed and imaged the results in 3D along with the high-resolution satellite imagery and physiographic vector data, allowing them to optimize the drilling program both for ice-based vertical holes designed to test the root of the kimberlite and for angled holes from land.
The next step for MLD is to correlate the results of a till sampling program from areas where there is a combination of historic geophysics and indicator minerals with the recent geophysics to derive the final target selection.
MLD has applied for a drilling permit and Brockington hopes to begin drilling the lake-covered targets next winter. The goal is to collect a large enough sample of any kimberlite the company might intersect (a couple of hundred kilograms) in order to complete microdiamond analysis.
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