Canadian explorer Nine Mile Metals expects borehole electromagnetic surveys to help it improve drill targeting over a wide area at key prospects in its Bathurst mining district landholding in New Brunswick.
Management said EarthEx Geophysical Solutions had been engaged to do two BHEM surveys, at its California and Wedge volcanogenic massive sulphide (VMS) targets, starting early next month.
“Borehole EM surveying is a high-resolution time domain EM technology that involves the laying of a transmitting loop to the side of the projected drill hole, followed by dropping a survey probe down the hole to detect the electrical conductivity of the adjacent rocks,” Nine Mile said.
“Many factors are taken into consideration in the survey design including the depth of the hole, its position relative to the target, the geology of the country rock, and the specified target.”
At California Lake a proposed 800m-by-800m loop could give a 500-700m search radius.
Previous deep drilling into Flat Landing Brook felsic volcanics, including “extremely siliceous host rocks”, was challenging, Nine Mile director and exploration VP Gary Lohman said.
In addition to burning drill bits, drilling was slow, at times cutting only 1m per hour.
The BHEM survey would allow Nine Mile to see conductivity deeper and in all directions from the probe.
“Borehole geophysics on both drill holes will provide the team with further direction prior to additional drilling,” Lohman said.
“It is imperative we revisit [drill-hole] CL-23-10-01 with BHEM prior to additional drilling.
“In addition to being cost effective, the BHEM survey will delineate potential targets below the end of the present drill hole, while also evaluating the adjacent stratigraphy where we have the convergence of three conductors at Target area 10.
“We are in the right stratigraphy and multiple sources have identified a favorable VMS target environment at depth adjacent to and flanking the drill hole.”
Lohman said historical mining below 500 feet at Wedge was limited.
BHEM results and recent drill assays combined in a new 3D model would help guide the next phase of drilling.
“We look forward to commencing work in early June and advancing the California Lake VMS program, utilising the best technology and data processing available,” Lohman said.
The circa-3800-square-kilometre Bathurst Mining Camp is one of the largest VMS fields in the world.
