First Cobalt starts borehole survey programme

First Cobalt starts borehole survey programme

First Cobalt announced that it has started the 2018 borehole geophysical and optical televiewer survey programme to test holes drilled in Cobalt South and for the first time in Cobalt North.

The borehole programme is intended to expand known zones of cobalt mineralisation and further define the controlling structures in these two areas. The borehole geophysical data will also be used to assess ground geophysical methods for detecting blind cobalt mineralisation elsewhere in the Cobalt Camp. “Combining survey data with assay results and geological logs allows for quicker assessment and follow-up during the next stage of drilling,” comments Dr Frank Santaguida.

The 2018 borehole geophysical and optical televiewer survey programme is designed to improve understanding of the controlling structures in the mineralised system as borehole surveys provide more accurate data than surface geophysics and aerial surveys. By improving the understanding of the broader structural environment, First Cobalt anticipates it will be better able predict where other mineralized structures may lie. “Borehole televiewer surveys are a relatively modern mineral exploration tool that will help map previously mined silver vein systems and could spatially define mineralization trends to predict where cobalt mineralization occurs,” adds Santaguida.

In 2017, the company conducted magnetism, resistivity and televiewer surveys on historic holes at the Keeley and Frontier mines in Cobalt South prior to drilling. Magnetic data were used to model the Nipissing Diabase and Archean volcanic rocks in 3D, where outcrops are sparse and in the subsurface below the Huronian sedimentary rocks.

Silver-cobalt mineralisation typically occurs within a few hundred metres of the Diabase contact, so mapping this contact is important for exploration targeting. Resistivity data for the host rocks to mineralisation were used to interpret electromagnetic data within the mineralised zones to determine potential for further mineralisation offhole. This method was successfully applied in the Keeley South Zone to define new drill targets.

The 2018 geophysical surveys in this programme will measure magnetism, resistivity, natural gamma radiation and induced conductivity to characterize mineralised zones and their host rocks.

Recent holes drilled at the Kerr Lake area of Cobalt North and the Woods Extension Zone in Cobalt South intersected breccia-hosted sulphide mineralization interpreted to be developed within structures hosting cobalt, silver and nickel. Borehole geophysical surveys have not previously been conducted in Cobalt North. The resistivity and induced conductivity surveys are intended to characterise this style of mineralisation and help determine the orientation of the structures. In addition, the results will be used to assess if ground surveys may be applicable for further exploration.

Optical televiewer surveys in Cobalt South will provide detailed, in-situ structural information and will measure the true orientation of the lithological contacts. The televiewer images will allow for a better appreciation of the structural context within the holes. At Keeley South, where disseminated and broad zones of silver and cobalt mineralization were encountered, the televiewer images will be interpreted to find faults and fractures where drill core recovery was poor.

The televiewer interpretations will be integrated with the surface structural mapping information and geological logs from other nearby drill holes to predict extensions of known mineralisation and infer new areas for drill targeting. DGI Geoscience of Toronto, Ontario was engaged to conduct the borehole survey work.


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